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Coal-accompanying gas is an essential resource, with numerous mining methods. The practice has proved that injecting high-pressure air into the coal seam can replace and flush the gas in the coal seam, effectively solving the problem of inadequate single gas drainage in soft and low permeability coal seams. This paper uses the finite element method to solve the model, simulate and study the gas drainage by high-pressure air injection in the bedding drilling, and establish a fluid-structure coupling model for gas drainage by high-pressure air injection. The competitive adsorption of N2, O2, and CH4, diffusion and migration of CH4 in coal matrix and fissure, matrix deformation caused by CH4 adsorption, and desorption and control of coal deformation by applied stress are considered in the model. When the fixed extraction time is 600 days (d), the optimal spacing between the extraction hole and injection hole is 12.5 m. The safe extraction effect and minimum drilling amount can be ensured. It provides a basis for guiding gas drainage by injecting high-pressure air on-site. [ABSTRACT FROM AUTHOR]

This paper analyzes how imitation and innovation strategies of high-tech small and medium-sized enterprises (SMEs) impact their sustainable performances and also the whole business ecosystem with the NK-model that mimics the fitness landscape and simulates enterprises' choice of technological strategy in response to causal ambiguity and environmental complexity. Our study yielded three findings: (1) When the imitation barriers are low, the imitation strategy of high-tech SMEs has a better effect on the performance improvement in the early stage of the operation than the innovation strategy. In the long run, high-tech SMEs exhibit innovation, which plays a greater and more lasting role in enhancing sustainable performance. On the contrary, it is always difficult for imitators to realize significant performance improvement, (2) In a simple environment, imitation strategy plays a more effective role in improving high-tech SMEs' performance, whereas in a complex environment, innovation strategy is more conducive to discovering opportunities, and it issues from high levels of competition, and (3) more importantly, the simulation finds that the innovation of high-tech SMEs contributes more to the performance of the business ecosystem as a whole. The introduction of the NK-model simulation method in the research of technological strategies and the new scope of looking at the strategies in the business ecosystem provide new research venues for the literature. [ABSTRACT FROM AUTHOR]

The traditional anchoring method of bolts has insufficient control over the surrounding rock of the coal roadway. Based on this background, full-stress anchoring technology of bolts was proposed. Firstly, a mechanical relationship model of a bolt-drawing, anchoring interface was established to obtain the equations of the axial force and obtain shear stress distribution as well as the decreasing-load transfer law of the anchoring section of bolts. Through studying the prestress-loading experimental device of bolts, we found that increasing the initial preload could increase the axial force under the same conditions and the retarded anchoring section could control the axial-force loss of bolts in the middle of the anchoring section. Under the full-stress anchoring mode, the effect of applying a pre-tightening force was better than that of applying a pre-tightening force under traditional anchoring methods. Moreover, FLAC3D (Fast Lagrangian Analysis of Continua 3D; ITASCA (Ita sca International Inc), Minnesota, USA) numerical simulation calculation was performed. Under the full-stress anchoring mode of bolts, the increased anchoring length reduced the damage of the anchoring section, with a wider control range of the rock formation and higher strength of the compressive-stress anchoring zone. Based on the above research, four methods for applying the full-stress anchoring technology of bolts in engineering were proposed. The full-stress anchoring technology of bolts in the coal roadway has been applied in the support project of the return-air roadway at working face 3204 of the Taitou Coking Coal Mine of the Xiangning Coking Coal Group, Shanxi. The maximum moving distance of the roof and floor of the roadway was reduced from 200 to 42 mm, and the maximum moving distance on both coal sides was reduced from 330 to 86 mm. The full-stress anchoring technology of bolts was able to control the surrounding rock in the coal roadway. [ABSTRACT FROM AUTHOR]