Maintaining surrounding rock mass stability of roadways is essential to the safety of deep coal mining. In this study, the No. 2‐2092 roadway of the No. 2‐209 mining face in Ganhe coal was taken as the target roadway for field analysis. The selected region can be considered a typical area with dominating geological tectonic stress, based on the geological survey and in situ stress results. A mechanical model of roadway overburdens was developed to analyse the large deformation and stress field distribution. It is found that the large deformation is caused by the combined superposed stress field including laterally transferred stress formed in structures at overlying strata, mining‐induced advanced abutment pressure, and the regional in situ stress. Thus, a Two‐Direction Hydrofracturing Technique (TDHT) was proposed to reduce the pressure of the No. 2‐2092 roadway by altering the roof structure in the influenced zones. Compared with the original roadway without fracturing, it is found that the roof to floor convergence has dropped by nearly 47% after fracturing; the displacement of sidewalls has reduced by almost 31%, demonstrating the effectiveness of the proposed method in pressure relief. Results from this study can provide guidance on controlling the large deformation of roadways in deep underground mines.

A new type of similar material considering water characteristics is developed through orthogonal experiments. The similar material is composed of river sand, barite powder, cement, gypsum, and water. We determine the best test development process. First, the proportion test scheme is designed based on the orthogonal test. Then, the effects of the moisture content, mass ratio of aggregate to binder and other components on the density, uniaxial compressive strength, elastic model, and Poisson’s ratio of similar materials are analyzed by range analysis. Finally, the multiple linear regression equation between the parameters and the composition of similar materials is obtained, and the optimal composition ratio is determined according to the relationship between the test’s influencing factors and the mechanical properties of similar materials. The results show that the selected raw materials and their proportioning method are feasible. The content of barite powder plays a major role in controlling the density and Poisson’s ratio of similar materials. The mass ratio of aggregate to binder is the main factor that affects the uniaxial compressive strength and elastic modulus of similar materials, while the moisture content has the second largest effect on the density, uniaxial compressive strength, elastic modulus, and Poisson’s ratio of similar materials. When the residual moisture content increased from 0 to 4%, the uniaxial compressive strength and elastic modulus of similar materials decrease by 49.5% and 53.3%, respectively, and Poisson’s ratio increases by 54.8%. Determining the residual moisture content that matches the design of similar material model tests is critical to improving the test accuracy and provides a reference to prepare similar materials with different requirements.

A high power and high efficiency fully internally-matched GaN power amplifier operating at X-band is proposed. The device is realized by matching four GaN power bars of 18-mm gate periphery. To reduce the size, single layer capacitors with high permittivity are used, and the impedance matching circuits are fabricated on Al₂O₃ ceramic substrate. The device exhibits saturated output power of more than 660 W with power gain above 9.8 dB within the frequency range of 8.2–8.8 GHz, based on the pulse mode of 100 μs pulse width and 10% duty. In addition, the highest saturated output power and power added efficiency reach 705 W and 51.7% with packaging compact size (26 mm × 17.4 mm).

Artificial support system takes advantages of self-bearing capacity of surrounding rock mass in roadway support, which is one of the important supporting ideas in modern times. The implementation way of an artificial support system is worthy of deep investigation. In this study, an HLBR hypothesis was proposed with comprehensive consideration of mechanical properties of surrounding rock mass based on the reinforced arch theory and axial variation theory. A model of bearing structure in surrounding rock mass was constructed, and the stress state on the bearing structure was analyzed. It was believed that when the axial ratio (k) of this bearing structure is equal to the lateral stress factor (λ) (which is the optimal axial ratio), the tangential stress on the bearing boundary reaches the minimum and is in uniform distribution. At this moment, the roadway and the supporting structure can make good use of the self-carrying capacity of surrounding rock mass, which is conducive to lowering the stress distribution level of surrounding rock mass. According to prestress diffusion characteristics of bolt, some ways to achieve HLBR were proposed, which were the optimal axial ratio design, difference support and local grouting modification, and finally performance of the original support design in a belt roadway of the mining district IV of a mine in Shanxi Province. A new supporting scheme was provided according to the HLBR hypothesis. In addition, the FLAC3D strain-softening model was modified by C++, which was used to interpret the reasonability of the suggested supporting scheme. The proposed HLBR hypothesis discloses ways to use self-capacity of surrounding rock mass. This study provides a new idea for roadway sectional design and roadway support design, which are beneficial to maintaining the stability of surrounding rock mass in roadways.

The high concentration of CO generated in confined spaces following a gas explosion constitutes the primary lethal factor, and its rapid elimination represents a critical technical bottleneck in emergency rescue operations. This study systematically investigates the confined thermodynamic characteristics of CO catalytic oxidation over hopcalite across a wide temperature range of 15–65 °C. Based on the ideal gas assumption and constant-volume boundary conditions, the thermodynamic processes were classified into two categories: constant-volume variable-temperature and constant-temperature constant-volume. The influence of temperature on enthalpy change, heat release, entropy change, and the chemical equilibrium constant was quantitatively examined. The results demonstrate that the total enthalpy change and heat release remained negative throughout the entire temperature range, exhibiting a trend of “initial increase, subsequent decrease, followed by a slight rise”, with the maximum exothermic value observed at 25 °C. The total entropy change was persistently negative across the full temperature range; the positive offset contribution of the physical entropy change induced by temperature elevation was negligible, resulting in a consistently high absolute value of the total entropy change. The logarithm of the standard equilibrium constant decreased linearly with increasing temperature yet remained as high as 180.48 at 65 °C, indicating that the reaction maintains an extremely strong thermodynamic spontaneity and a nearly complete conversion limit under all tested conditions.