Aiming at potential emergency discharge required during at-sea testing of deep-sea polymetallic nodules lifting system consisting of pipeline and lifting pump, a theoretical calculation was conducted for the hydraulic system of emergency discharge mechanism for at-sea testing, and also a simulation analysis was conducted with AMEsim. It is found that the reliability coefficient of AMEsim for the system is 0.86. An AMEsim-based hydraulic system model was established for the actuator in an at-sea test at 500 m depth. The simulation results show that the oil pipeline in the hydraulic system is 16 mm in diameter, with the set pressure not less than 10.47 MPa, and the action time of actuator is 6 s. This research results can provide a reference for the design of emergency discharge mechanism.

The numerical simulation was used to establish a single-hole blasting model, which was then used to simulate the blasting effect with different stemming length. Otsu thresholding technique was adopted for image segmentation, and the data, such as percentage of cracked rock area, fractal dimension of pore structure, and fragmentation of rock mass, were extracted for comparative analysis, so as to explore the influence of stemming length on damage effect under deep-hole blasting. The results show that fractal dimension and percentage of cracked rock area are in an uptrend before falling down as stemming length increases. The fractal dimension reaches the maximum value with stemming length of 3.0 m, and the percentage of cracked rock area reaches the maximum value with stemming length of 1.7 m. Stemming length of 2.2 m can bring the highest number of fragments, and stemming length of 2.0 m can result in the smallest average area of fragments. It is found that the blasting with the stemming length of 2.0-2.2 m can lead to better rock fragmentation effect. As the stemming length increases, the flyrock becomes bigger, and the displacement distance decreases. The research results can be taken as reference in selection of stemming parameters for blasting operation.

Manganese-containing master alloy was prepared by vacuum induction melting. Effects of factors, such as manganese source, Mn/Al mass ratio, preheating time, and refining time on the composition of the manganese-containing master alloy were studied, and the influence of manganese-containing master alloys replacing the traditional “Mn + Al” feed on the prepared manganese-containing AB₅-type rare-earth-based hydrogen storage alloy was also discussed. The experimental results show that compared to manganese powder, manganese flakes as manganese source can bring higher melting yield. Manganese-containing master alloys can be formed with different Mn/Al mass ratios. As the preheating time is prolonged, the melting yield firstly increases and then decreases, and the optimal condition for preheating is 10 minutes at a power of 4 kW. As the refining time increases, the melting yield decreases slightly, and the optimal condition for refining is 1 minute at a power of 15 kW. The average melting yields of rare-earth-based hydrogen storage alloy prepared with MnAlNi alloy and MnAl alloy are increased by 0.37% and 0.78% respectively than that with “Mn + Al” as raw material. The preparation of AB₅-type rare-earth-based hydrogen storage alloy with manganese-containing master alloy can optimize the yield, with the hydrogen storage performance not influenced. The application of this method in practical industrial production brings good effect.

For phosphorus-iron waste left after lithium extraction from cathode powder of spent lithium iron phosphate (LFP) batteries, a selective leaching with sulfuric acid was adopted to remove impurities therein. The results indicate that after a 4-stage leaching at 80 ℃ for 2 h, with a sulfuric acid at a concentration of 0.32 mol/L and a liquid-to-solid ratio of 5 mL/g, the total leaching rates of elemental impurities, including Cu, Mn, Al, Ca, Na and Mg reach 70.81%, 68.33%, 65.57%, 68.03%, 67.85% and 64.28%, respectively, and the total leaching rates of P and Fe are only 2.52% and 2.24%, respectively. It is concluded that the main elemental impurities can be effectively leached out from such phosphorus-iron waste, with elements of P and Fe left for subsequent resource utilization.

Influence of Al content on the microstructure, phases, hardness, tensile and impact properties of quenched and tempered 4Cr5MoVSi die steel was studied by using optical microscopy, transmission electron microscopy (TEM), tensile testing machine among other instruments. It is found martensite is formed in the quenched and tempered 4Cr5MoVSi die steel with Al content of 0-0.6% (mass fraction, the same below), while martensite plus δ ferrite are formed in the quenched and tempered 4Cr5MoVSi die steel with Al content of 1.2%-1.8%. Without adding Al or with an addition of 0.3%-1.8% Al, 4Cr5MoVSi die steel after quench and tempering has α-Fe and M₇C₃ formed as its main phases. The 4Cr5MoVSi die steel with an Al content of 0.3%-1.2% has its relatively small variation in its hardness after quenching and tempering; however, with Al content up to 1.8%, the quenched and tempered die steel has its hardness significantly reduced. It is concluded that an appropriate addition of Al is beneficial to improvement in the room-temperature tensile strength, elongation at break, and impact toughness of quenched and tempered 4Cr5MoVSi die steel; with an addition of 1.2% Al, the quenched and tempered 4Cr5MoVSi die steel can have higher hardness, strength, and impact toughness.

To reveal the relationship among uniaxial compressive strength, tensile strength and shear strength, 159 sets of rock mechanics data collected from 38 mines were taken as samples. Firstly, the relationship between uniaxial compressive strength and tensile strength was characterized by data analysis, and the range of uniaxial compressive and tensile strength in the formulae for calculating shear strength was calibrated. Then, a BP neural network prediction model was constructed, with which the shear strength of rocks can be predicted with uniaxial compressive strength and tensile strength as the input layer. The results show that: the uniaxial compressive strength of rock is 7.6-27.8 times tensile strength; the cohesion value obtained from multiple comparison tests is 1.0-2.2 times that from the original empirical formula, and the tangent value of internal friction angle is 0.35-1.00 times that from the original empirical formula, presenting high confident and reliable results; based on comparison between the predicted value with BP neural network and the actual value, the cohesion deviation ranges from -10.53 MPa to 20.12 MPa, and the internal friction angle deviation ranges from -18.43° to 28.97°, exhibiting an overall normal distribution.

To investigate the rheological properties of heat-treatment-free AlSi9MnMg alloy specifically for high-pressure die casting (HPDC) process, influence of temperature and shear rate on the viscosity of molten alloy was studied by using a rotational rheometer based on the Searle principle, and the microstructure of the samples in rheological testing was analyzed. The results indicate that the viscosity of molten alloy decreases as the temperature rises in the test. At a given temperature, the viscosity decreases as the shear rate increases. With the shear rate exceeding 800 s^-1, the viscosity remains unchanged with shear time at the same shear rate. Under the action of shear force, the dendritic grains in the melt undergo fragmentation, agglomeration and spheroidization. Moreover, as the temperature rises in the test, the particle agglomerates become smaller in size.

To enhance the positioning accuracy of seismic source in underground mining and solve the problem of spatiotemporal changes in the wave velocity field caused by excavation disturbance and complex structures, seismic source relocation with real-time inversion of wave velocity field as a prior was proposed, which combined ray tracing and quasi-Newton iteration algorithm to realize dynamic update of wave velocity field and high-precision positioning of seismic source. The validity of this method was verified by synthetic monitoring and field testing. The synthetic monitoring results showed that compared to the least squares procedure, the real-time inversion resulted in the average positioning accuracy enhanced by 49.8% and the accuracy of wave velocity inversion exceeding 95%. In the field testing, a 180 m×180 m to-be-filled area in mining operation was taken for imaging target. Compared to the least squares procedure, this method brought the average error in positioning reduced by 7.074 m, and the accuracy of wave velocity inversion in each region exceeding 95%. The research indicates that this method not only is suitable for seismic source positioning in microseismic monitoring, but also can be used as a geophysical method for detecting passive imaging of goaf areas.

The polymetallic ore from Shizhuyuan of Hunan Province was taken for research. Based on the characteristics of uneven coarse-fine dissemination of minerals and insufficient deliberation of Mo-Bi sulfide ore for flotation, an enhanced recovery technology by stepwise separation was developed for the low-grade Mo-Bi sulfide ore. The results show that an experiment by adopting such stepwise separation technique produced a bulk flotation concentrate grading 1.31% Mo and 2.83% Bi at corresponding recoveries of 88.43% and 85.99%, presenting 5.34 and 4.80 percentage points up, respectively, compared to on-site conventional bulk flotation process. This creates favorable conditions for the following tungsten flotation from the bulk flotation tailings. It is shown that a closed-circuit tungsten flotation can produce a tungsten concentrate grading 44.64% WO₃ at 84.12% recovery.

As for fracture development and potential instability in the open-pit bench slopes in Dabaoshan in Guangdong Province, the blockiness was proposed to be taken as a quantitative measure of rock mass integrity. Based on the existing data, 72 potentially unstable zones on the western slope were identified. The structural characteristics of the rock mass were analyzed based on investigation of fracture occurrence characteristics and 3D fracture network modeling, and rock mass integrity was also evaluated by blockiness analysis. It is found that there are fully-developed fractures with good ductility in all the zones, creating the structural conditions for block formation; in 84.9% of the zones, the inclination angle of superior fractures and the slope inclination angle are supplementary, which can significantly reduce sliding risks; in 97.3% of the zones, the blockiness of rock mass is less than 27, indicating mild blockiness, good integrity of rock mass, and overall high stability. There are only rock mass with blockiness over 27 in Zone 6^# and Zone 46^#, presenting moderate blockiness. In these two zones, the rock mass structure is significantly degraded, leading to reduction in damage tolerance. It is concluded that there are potential risk of slope instability in those two zones, which should be taken as the focus in the subsequent disaster prevention and control for the slopes in Dabaoshan.