Numerical Study on Reasonable Entry Layout of Lower Seam in Multi-seam Mining

Abstract: According to the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, reasonable entry layout of lower seam in multi-seam mining has been studied by FLAC3D numerical simulation. Three ways of entry layout including alternate internal entry layout, alternate exterior entry layout and overlapping entry layout has been put forward for discussing on reasonable entry layout. Then stress distribution and displacement characteristics of surrounding rock have been analyzed in the three ways of entry layout by numerical simulation, leading to the conclusion that alternate internal entry layout pattern, which make the entry located in stress reduce zone and avoid the influence of abutment pressure of upper coal seam mining to a certain extent, is a better choice for multi-seam mining. The research results herein can offer beneficial reference for entry layout with similar geological conditions in multi-seam minin

SuperLine3D: Self-supervised Line Segmentation and Description for LiDAR Point Cloud

Poles and building edges are frequently observable objects on urban roads, conveying reliable hints for various computer vision tasks. To repetitively extract them as features and perform association between discrete LiDAR frames for registration, we propose the first learning-based feature segmentation and description model for 3D lines in LiDAR point cloud. To train our model without the time consuming and tedious data labeling process, we first generate synthetic primitives for the basic appearance of target lines, and build an iterative line auto-labeling process to gradually refine line labels on real LiDAR scans. Our segmentation model can extract lines under arbitrary scale perturbations, and we use shared EdgeConv encoder layers to train the two segmentation and descriptor heads jointly. Base on the model, we can build a highly-available global registration module for point cloud registration, in conditions without initial transformation hints. Experiments have demonstrated that our line-based registration method is highly competitive to state-of-the-art point-based approaches. Our code is available at https://github.com/zxrzju/SuperLine3D.git.Comment: 17 pages, ECCV 2022 Accepte

Isoflurane-Induced Spatial Memory Impairment in Mice is Prevented by the Acetylcholinesterase Inhibitor Donepezil

Although many studies have shown that isoflurane exposure impairs spatial memory in aged animals, there are no clinical treatments available to prevent this memory deficit. The anticholinergic properties of volatile anesthetics are a biologically plausible cause of cognitive dysfunction in elderly subjects. We hypothesized that pretreatment with the acetylcholinesterase inhibitor donepezil, which has been approved by the Food and Drug Administration (FDA) for the treatment of Alzheimer's disease, prevents isoflurane-induced spatial memory impairment in aged mice. In present study, eighteen-month-old mice were administered donepezil (5 mg/kg) or an equal volume of saline by oral gavage with a feeding needle for four weeks. Then the mice were exposed to isoflurane (1.2%) for six hours. Two weeks later, mice were subjected to the Morris water maze to examine the impairment of spatial memory after exposure to isoflurane. After the behavioral test, the mice were sacrificed, and the protein expression level of acetylcholinesterase (AChE), choline acetylase (ChAT) and α7 nicotinic receptor (α7-nAChR) were measured in the brain. Each group consisted of 12 mice. We found that isoflurane exposure for six hours impaired the spatial memory of the mice. Compared with the control group, isoflurane exposure dramatically decreased the protein level of ChAT, but not AChE or α7-nAChR. Donepezil prevented isoflurane-induced spatial memory impairments and increased ChAT levels, which were downregulated by isoflurane. In conclusions, pretreatment with the AChE inhibitor donepezil prevented isoflurane-induced spatial memory impairment in aged mice. The mechanism was associated with the upregulation of ChAT, which was decreased by isoflurane

Effect of regional anesthesia on the postoperative delirium: A systematic review and meta-analysis of randomized controlled trials

ObjectivePostoperative delirium (POD) starts in the recovery room and occurs up to 5 days after surgery. However, the POD guidelines issued by the European Society of Anesthesiology (ESA) suggest that the effect of regional anesthesia on POD is controversial. This meta-analysis aims to investigate whether perioperative regional anesthesia reduced the incidence of POD.MethodsStandard Published randomized controlled trails (RCTs) were searched from bibliographic databases to identify all evidence that reported regional anesthesia assessing incident delirium following diverse surgeries. The primary outcome was the incidence of POD, and the secondary outcomes were POD scores, pain scores, and emergence time. The relative risk (RR) for dichotomous outcomes and the weighted or standardized mean difference (WMD, SMD) for continuous outcomes were estimated using a random-effects model.ResultsTwenty RCTs with 2110 randomized participants undergoing different surgeries were included. Meta-analysis showed that regional anesthesia was associated with less POD incidence compared to general anesthesia (total intravenous anesthesia (TIVA) or inhalation anesthesia) (relative risk (RR) = 0.62, 95% confidence interval (CI) = 0.45–0.85)). Subgroup analysis showed that the decrease in POD incidence was associated with a nerve block (0.46, 95% CI = 0.32–0.67) and regional-combined-general anesthesia (0.42, 95% CI = 0.29–0.60). Regional anesthesia significantly reduced POD incidence in the recovery room after pediatric surgeries (0.41, 95% CI = 0.29–0.56). Regional anesthesia also reduced the POD score (SMD −0.93, 95% CI = −1.55 to −0.31) and pain score (SMD −0.95, 95% CI = −1.72 to −0.81). There was no significant difference in emergence time between regional anesthesia and general anesthesia (WMD −1.40, 95% CI = −3.83 to 6.63).ConclusionsThere was a significant correlation between regional anesthesia and the decrease in POD incidence, POD score, and pain score

Mechanical response analysis of surrounding rock bearing structure of soft rock roadway based on full-length anchorage

A mechanical model of full-length anchoring bolt is established to study the stability of mechanical bearing structure of surrounding rock in high stress soft rock roadway after full-length anchoring bolt. The model considers the dilatancy characteristics of soft rock post-peak strength softening and the stress boundary conditions of full-length bolt, and the analytical formula of bolt stress is derived. Furthermore, the mechanical model of full-length anchored surrounding rock is established by equivalent the anchoring force to the form of volume force. From shallow to deep, it is divided into anchorage residual zone, anchorage plastic softening zone, non-anchorage plastic softening zone and elastic zone, and the stress expression of each zone is deduced. Combined with engineering examples, the influence of space effect, expansion coefficient, bolt length and tray reaction force on surrounding rock stress and bolt stress is analyzed. The results show that under the influence of spatial effect, the deformation and failure of roadway presents progressive development. The concept of ' anchorage control zone ' is proposed, that is, in the process of full-length bolt support, the virtual support force and anchoring force of surrounding rock are in a state of reciprocal growth and decline, thus inhibiting the transfer of surrounding rock stress to the deep and effectively reducing the plastic zone. The earlier the anchor bolt is installed, the greater the deformation of the surrounding rock acting on the rod body, and the easier it is to form a common bearing body with the surrounding rock. The axial force of the anchor bolt is proportional to the expansion coefficient. With the increase of the expansion coefficient, the growth rate of the anchoring force is significantly accelerated, which ensures the recovery effect of the anchor bolt on the radial stress of the surrounding rock. The axial force distribution and peak value of the rod body will increase with the increase of the length of the bolt and the bonding range of the surrounding rock/anchoring agent interface, and then the peak area of the tangential stress of the surrounding rock will shift to the direction of the tunnel wall. The effect of the reaction force of the full-length bolt tray is mainly reflected in improving the stress of the bolt, giving full play to the anchoring effect of the bolt and the ability to protect the surface, and having little effect on the boundary of the residual zone and the plastic zone

Anisotropy and energy evolution mechanism of rock mass under true triaxial loading-unloading

In the process of underground excavation, the surrounding rock is in a very complex stress environment, especially under the influence of its anisotropy, the occurrence of dynamic disaster is hidden. In this paper, the loading and unloading tests of sandstone in different principal stress directions were carried out by using the true triaxial unloading disturbed rock test system. The mechanical properties and failure characteristics of true triaxial under different principal stresses were studied, the energy evolution mechanism in other directions induced by loading and unloading of different principal stresses was analyzed. Results showed that under the influence of rock mass secondary stress anisotropy, during the cyclic loading and unloading process of the first principal stress, the strain in other directions shows opposite deformation. The volumetric strain compresses first and then expands, and the final volumetric strain shows a macroscopic phenomenon of expansion. When the third principal stress of high confining pressure rock mass is unloaded, the first principal stress produces a compression deformation, while the second and third principal stresses produce an expansion deformation. The deformation of the second principal stress is less than that of the third principal stress, and the deformation in unloading direction changes from linear elastic state to elastic-plastic nonlinear state. The accumulated energy of rock mass is a great difference between the first principal stress unloading and the third principal stress unloading. The energy variation characteristics of unloading in the dominant direction determine the energy accumulation and release law in the other two induced directions. The limit stored energy of the third principal stress unloading rock decreases, and the second principal stress accelerates the rock failure with the increase of the first principal stress, which verifies that the rock is easier to be destroyed by unloading than by loading. The higher the unloading rate of the third principal stress, the higher the energy released and the lower the dissipated energy, and the lower the energy density and total accumulated energy density in the unloading direction of rock mass. The main cause of dynamic accidents is the accumulation and release of energy in rock mass. The secondary anisotropy of rock mass has a great influence on the ultimate stored energy of rock mass. The study on the influence characteristics of three-dimensional loading and unloading secondary stress on the ultimate stored energy of rock mass provides a reference for preventing rock burst

Neuroinflammation Induced by Surgery Does Not Impair the Reference Memory of Young Adult Mice

Postoperative cognitive dysfunction (POCD) increases morbidity and mortality after surgery. But the underlying mechanism is not clear yet. While age is now accepted as the top one risk factor for POCD, results from studies investigating postoperative cognitive functions in adults have been controversial, and data about the very young adult individuals are lacking. The present study investigated the spatial reference memory, IL-1 , IL-6, and microglia activation changes in the hippocampus in 2-month-old mice after anesthesia and surgery. We found that hippocampal IL-1 and IL-6 increased at 6 hours after surgery. Microglia were profoundly activated in the hippocampus 6 to 24 hours after surgery. However, no significant behavior changes were found in these mice. These results indicate that although anesthesia and surgery led to neuroinflammation, the latter was insufficient to impair the spatial reference memory of young adult mice