Intelligent Trajectory Design for RIS-NOMA aided Multi-robot Communications

A novel reconfigurable intelligent surface-aided multi-robot network is proposed, where multiple mobile robots are served by an access point (AP) through non-orthogonal multiple access (NOMA). The goal is to maximize the sum-rate of whole trajectories for multi-robot system by jointly optimizing trajectories and NOMA decoding orders of robots, phase-shift coefficients of the RIS, and the power allocation of the AP, subject to predicted initial and final positions of robots and the quality of service (QoS) of each robot. To tackle this problem, an integrated machine learning (ML) scheme is proposed, which combines long short-term memory (LSTM)-autoregressive integrated moving average (ARIMA) model and dueling double deep Q-network (D$^{3}$QN) algorithm. For initial and final position prediction for robots, the LSTM-ARIMA is able to overcome the problem of gradient vanishment of non-stationary and non-linear sequences of data. For jointly determining the phase shift matrix and robots' trajectories, D$^{3}$QN is invoked for solving the problem of action value overestimation. Based on the proposed scheme, each robot holds a global optimal trajectory based on the maximum sum-rate of a whole trajectory, which reveals that robots pursue long-term benefits for whole trajectory design. Numerical results demonstrated that: 1) LSTM-ARIMA model provides high accuracy predicting model; 2) The proposed D$^{3}$QN algorithm can achieve fast average convergence; 3) The RIS with higher resolution bits offers a bigger sum-rate of trajectories than lower resolution bits; and 4) RIS-NOMA networks have superior network performance compared to RIS-aided orthogonal counterparts

Novel Segmented Roadside Plugging-Filling Mining Method and Overlying Rock Mechanical Mechanism Analyses

The no-pillar mining method is widely used in coal mining engineering because of its superiority in resolving mine pressure hazards and protecting natural resources. In view of the geological conditions of stable strata in a coal mine of the Shandong Coal Zone, a novel segmented roadside plugging-filling mining method is proposed by introducing the filling coefficient into roadside filling. The operation process is designed with a new grouting filling forming device. Based on the relationship between the theoretical deflection of a cantilever beam and geometric settlement and parallel settlement models, strength formulas applicable to the segmented roadside plugging-filling (SRPF) method at different migration stages are obtained, and the deformation formulas of a roadway toward a rock slab are solved by an elastic equivalent model. Further, the determination procedure of the filling mode under the mining method is clarified. The SRPF method was implemented on a test stope, and the test results indicated that the theoretical deformation produced by the SRPF method was small and can meet the mining requirements. Through on-site test monitoring, the deformation of surrounding rock was 0−160 mm and the filling body under the SRPF method could maintain its own strength and the stability of the surrounding rock. In addition, entire successful mining been completed in the working stope, which further proves the applicability of this method. The backfilling cost of the gob-side filling was reduced by approximately 50%, and the backfilling efficiency was improved in the mine. The description of the novel mining method may provide theoretical and practical guidance for coal mining in similar geological conditions

Stability analysis of grouting surrounding rock in fracture zone in coal seam floor

Affected by the geological concealment and complexity, there is a potential safety risk of mining induced damage due to insufficient grouting in fissures. Based on the analysis method of combining numerical simulation and microseismic monitoring, the grouting treatment effect of water conducting channel is analyzed based on the background of the grouting floor of 1612A working face in Zhangji Coal Mine. The influence of mining stress and the stability of grouting rock mass are revealed before and after grouting. The results show that: compared with the non-grouting, the abnormal stress area of surrounding rock decreases. The coupling is no longer connected to the working face. After 10 m away from the roadway side, the disturbance degree decreases with the increase of distance. Microseismic monitoring further verified the calculation results: the rock fracture signal “detours” in the grouting affected area. The number of microseismic events in surrounding rock area is small, and the grouted rock mass is in stable state

Correction to: Contrasting transcriptional responses of PYR1/PYL/RCAR ABA receptors to ABA or dehydration stress between maize seedling leaves and roots

Following publication of the original article [1], a reader spotted that the article appears to have some misplaced/duplicated figures. In particular, Fig. 5a and Fig. 6a appear to be identical, and do not match what is written in the text. The authors apologized for this oversight and supplied the original pictures, which are reproduced below

Depth determination of floor crack zone in coal mining face of Group A in Huainan Mining Area

The production mines of Huainan Mining Area have already mined Group A coal, which is seriously threatened by deep high-pressure water, in order to solve the problem of the applicability of the traditional coal seam floor mining failure depth empirical formula, based on the production geological parameters of the Huainan Mining Area, the statistical software SPSS is used to analyze the partial correlation of various parameters, optimize the traditional damage depth calculation formula, and apply the fitting formula to the calculation of the floor damage of the 1612A working face in Zhangji Coal Mine; based on numerical simulation and micro-seismic monitoring are used to verify the accuracy of the formula calculation. The research results show that the coal seam thickness and other parameters are related to the depth of the fissure zone; a new calculation formula is obtained by fitting, and the calculated failure depth of the working face reaches 27.33 m, which is consistent with the fracture zone depth of 28 m measured by water injection test and 30 m calculated by numerical method; the concentration and distribution of micro-seismic events monitored on site are used to obtain a concentration depth of 30-35 m for the micro-fracture of the bottom plate

Identification method of hidden structure reactivation based on microseismic and numerical simulation

The microseismic monitoring can be used to identify and predict the activations strength of rock breaking, faults or hidden structures, and the use of numerical simulation technology can realize the inversion and reproduction of the stress field in the structural activation zone, the two complement each other, which can realize stress disturbance- stress concentration- local micro fracture- stress migration captured from internal cause to the appearance in the whole activation process of hidden structure. Based on the production and geological conditions of 1612A working face in Zhangji Coal Mine of Huaihe Energy Group, and the microseismic(MS) monitoring system, the temporal and spatial distribution characteristics of MS events were analyzed in the stope. The relationship between microseismic activity and fault activation was explored. And the identification method of hidden structure activation was proposed with the inversion of numerical simulation based on the MS data. The results show that, the MS events in the stope had typical time-phased and spatial regional distribution characteristics. Combined with the source parameters, it is determined that there is an abnormal area near the faults of F1611A76-F1611A7677, which was suspected to be a derivative fault of these faults. Through numerical simulation of the stress changes under two conditions to respond to the energy release law, the inversion results indicated that there were hidden structures in the measured area. Through field survey and trough wave geophysical exploration, it was found that there were typical broken abnormal areas in the specific range, which further verified the feasibility and accuracy of MS monitoring combined with numerical simulation to identify the activation of hidden structures

Grouting Mechanism in Water-Bearing Fractured Rock Based on Two-Phase Flow

Grouting is always used in mine water plugging, reinforcement, and other disaster prevention projects. The diffusion mechanism of slurry in fractured rock is affected by geological environment and slurry performance, which should be revealed and characterized better. Based on the two-phase flow diffusion theory, a slurry diffusion model considering flowing water condition was established for a blocking area of a fracture zone in one case from China. The feasibility of two-phase flow model in grouting diffusion calculation was analyzed. The diffusion model in dynamic water environment was studied, and the diffusion range varying with time in the grouting area of Zhangji Coal Mine was explored. The optimization method of multi grouting holes was put forward, and the influence of water flowing was discussed. The results show that the slurry diffusion calculated by the two-phase flow model was feasible and consistent with the experimental study. The dynamic water can change the conventional circular diffusion state of slurry, but its pattern was oval and leaf type. There were different penetration distances in directions, and typical grouting voids were made on the side and upstream. When the single-hole grouting was carried out, the predetermined value can be achieved in the height range, but it was only about 15 m on the side because of the water flowing, which cannot meet the requirements. The optimization scheme of grouting was put forward, which adopted multiple grouting holes in the long side, and grouting in different directions and periods to avoid the possible problems of multihole intersection. The rationality and effectiveness of the proposed optimization method were verified through the calculation of water yield and analysis of cement composition from the drilling core in the grouted zone. In the grouting process, the water flowing has double effects, which has a significant role in promoting and scouring along the flow direction, but there is a significant weakness in the side diffusion. It is very important to realize the rational use of the dynamic water through the optimization scheme. This study is an important basic work of grouting mechanism, and it is expected to promote the development of grouting technology and application of two-phase fluid-solid coupling theory