The No. 2₁ coal seam in the Zhengzhou mining area is a soft, three-layer, low-permeability coal seam prone to outbursts. The three-layer structure includes the coal seam and the roof and floor layers, which exhibit high gas contents and poor permeability. The dynamic hazards caused by coal and gas outbursts are very serious. A new permeability-increasing fracturing technique that combines hydraulic perforation and hydraulic fracturing was developed specifically for the geologic conditions of the gas-bearing No. 2₁ coal seam. Numerical simulations were developed to study the influence of the technique on the stress distribution and permeability of the coal around the borehole. In addition, the extracted borehole gas concentrations and extraction amounts at multiple sites were investigated before and after using the technique. The study shows that the permeability-increasing fracturing technique destroys the concentrated stress coal pillars via the development of fractures between boreholes in exposed hydraulically perforated coal. The coal stress within the zone with an effective increase in permeability decreased by 30. Furthermore, the permeability in this zone increased by three times, and the average extracted gas concentration increased by over six times. The gas pressure in the No. 2₁ coal seam decreased from 1.1MPa to 0.4MPa, and the gas content decreased from 15.96m³/t to 5.6m³/t. All outburst prediction indexes measured on site did not exceed their respective limits. The technique not only effectively eliminated the dynamic hazards caused by coal and gas outbursts but also achieved efficient gas extraction in the Zhengzhou mining area.

Aiming at the problem that the traditional method has poor reliability and low sensitivity on locating the position of single-phase ground fault, this paper proposes a method based on energy discharge function. This method uses the waveform information of fault phase, based on the analysis of action characteristics of arc suppression coil and influence on phase voltage. For the non-fault section, the energy discharge function remain nearly unchanged when the system runs normally or during the process of fault happen. The value is a very small positive number. For the fault section, the trend of energy discharge function rises first and then goes down. It reaches the maximum value when the coil takes action and produce stable compensation current. Therefore, we can use the value of energy discharge function to decide the fault section. Finally, the feasibility, reliability and sensitivity of the method are verified by PSCAD/EMTDC software simulation.

In the past decade, open-source software (OSS) has become a very popular research topic in the field of software engineering. Because its code is open to the public, it has been pursued by programming teams all over the world, including those in universities, government agencies and enterprises. In addition to analyzing some famous OSS projects, researchers also studied OSS projects and their functions in GitHub. However, the evolution process and the rules of OSS projects in GitHub have not been widely investigated so we conducted in-depth research on this issue. We use the cellular automata (CA) in the field of system dynamics to model the OSS project, construct the evolution rules of the Gray wolf optimization (GWO) algorithm, define the objective vector, objective function and key optimization operators of GWO for OSS cellular evolution, and realize the intelligent acquisition of OSS project evolution rules in GitHub. In addition, we also selected the data of some OSS projects in GitHub from 2015 to 2020 for the simulation experiment. The experiment results show that the total accuracy of the simulation is 91.4%, which is consistent with real data.