In order to explore the reliability of type selection in the design of lift pipe for underwater transport system in deep sea mining, hydrodynamic parameters were checked with transport indices as input for design. Based on the settling velocity of polymetallic nodules, anti-fatigue threaded sleeve of P110 steel, with outer diameter of 244.48 mm and wall thickness of 20.24 mm, was selected for lift pipe. And a towing test performed in a pool shows that the resistance drag coefficient is 1.4 for the lift pipe at the upper end of the pump and 1.3 at the lower end of the pump. Hydrodynamic parameters were calculated and analyzed for the underwater transport system according to working conditions and launching conditions, showing that the safety factor of lift pipe can meet the requirements of API RP 2RD Standard. In the deep-sea polymetallic nodules mining test project, lift pipe in the at-sea acceptance test, with reliable joint connection, could meet the requirement for each transporting parameter, which has verified that the type selection of lift pipe in the design is acceptable.

The composition structure and operation process of mini seafloor crawler drill are briefly introduced. A multi-body dynamic model of mini seafloor crawler drill was established by using Recurdyn software. And then, a mechanical model was established for seafloor sediment based on an experimental study on mechanical properties of sediment soil. Dynamic simulation was also performed for the motion of mini crawler drill on seafloor. Results show that mini seafloor crawler drill runs on seafloor sediment with slight slippage and an elevation angle due to a certain sinking of seafloor sediment. It is found that the dynamic characteristics of mini seafloor crawler drill is significantly influenced by the mechanical properties of sediment (especially thin and soft sediment), and mini seafloor crawler drill running at a lower speed will bring greater influence to its dynamic characteristics.

A new directional core acoustic emission technique was used to measure in-situ stress of the gas storage reservoir construction area of the Zhangbei Comprehensive Energy Project in Hebei Province. Results show that three boreholes buried at depth of 90 m have the corresponding in-situ stress dominated by horizontal structural stress, with the maximum principal stress approximately in the same north-south direction. In addition, the circumferential wave velocity anisotropy analysis method was conducted for verification, and the results show that the maximum principal stress is in a direction consistent with the result obtained from the acoustic emission testing of borehole core, which further verifies the correctness of the measurement by acoustic emission technique for the borehole cores.

Calculation was made for four typical pipelines by adopting typical critical flow rate and frictional pressure drop calculation model. The precision of the model was analyzed by comparing the calculated value with the measured value of four pipelines. The results show that as for flow rate and pipe diameter, the calculated values from Wasp model, HAN Wenliang model, FEI Xiangjun model and LIU Dezhong model are in good agreement with the measured value, presenting the maximum deviation within the range of ± 15%. FEI Junxiang model presents higher precision in the calculation of frictional pressure drop, with the maximum deviation within the range of ± 10%, but also has certain margin in calculation. It is concluded that FEI Xiangjun model can provide an important basis and reference for the design of long-distance transportation.

The effects of different heat treatment regimes on the microstructure and properties of as-cast Mg-5Sn-1.5Al-1Zn-1Si alloy were investigated. The results indicate that during the dissolution of solid, as the dissolution time is prolongsed, the alloy dendrites gradually dissolve and the grains gradually spheroidize. It is shown that the appropriate dissolution parameter is 510 ℃ × 8 h, and the alloy after such treatment has an evenly distributed microstructure, with a trace of precipitation of fine second-phase particles from the matrix, and thus possesses a high elongation rate. The appropriate aging parameter for the alloy is 200 ℃ × 16 h, and due to precipitation and migration of the phases segregating at the grain boundary, the alloy after aging treatment possesses clear grain boundaries and a microstructure with high uniformity, and also has the yield strength up to 136.3 MPa, which is higher than that of the as-cast alloy by 16.5%. After a treatment including 8 hours of solid dissolution at 510 ℃ and 16 hours of aging at 200 ℃, the alloy has its uniformity and dispersion of the microstructure further improved, and its tensile strength and hardness reach to 178.2 MPa and 59.6HB, respectively, up by 21.6% and 23.4% compared to the as-cast alloy.

In order to obtain the information of landslide in forest area, a high-resolution digital terrain model was derived from LiDAR point cloud, and the data of landslide in forest area were extracted by Res-Unet network and persistent homology. The Fenghe Experimental Forest in Washington State of USA was selected for study, among which three areas were selected for quantitative analysis. Based on calculation, the extracted data of landslide in the forest area show an average precision of 79.7%, an average recall rate of 70.2%, and average F₁ of 65.5%. The extraction method based on Res-Unet and persistent homology can accurately identify most landslides in the research area. It is shown that by using deep learning and persistent homology, this extraction method can make up for the weakness of traditional remote sensing methods in extracting landslide information in vegetation covered areas, and also provide a technical support for landslide analysis.

With a water cut-off and slope reinforcement project in Tenglong open-pit mine in Hebei Province as the background, a three-dimensional numerical model was established for finite slope with a retaining wall. Firstly, this numerical model was verified for its validity, and then was adopted in numerical simulation and analysis for the distribution law of earth pressure on the back of wall under translational motion. The results show that as the bench becomes wider, the angle of inclination for sliding surface of finite slope falls down to zero first, and then is gradually increased. When the bench is 9 m wide, the numerical solution of passive earth pressure on the back of wall is almost consistent with the analytical solution in term of its variation rule, which fully verifies the validity of this numerical model. The passive earth pressure presents nonlinear distribution, and the active earth pressure presents convex curve distribution. With both the stability of retaining wall and the construction cost taken into consideration, it is recommended that the slope degree should be set at 30° and the bench should be 9 m wide.

The furnace slag generated from smelting of South African vanadium-titanium magnetite was taken in an experimental study by adopting direct reduction followed by melting, and then analyzed by XRD to investigate the effect of basicity on the metallurgical properties of the slag, as well as on the separation of iron from slag. Furthermore, the effect of basicity on the melting characteristics and viscosity of the slag were also explored. Results show that melting at 1 450 ℃ with the addition of carbon at an amount of 5%, the slag has its corresponding softening temperature, hemisphere temperature and flow temperature rising gradually with the increase in basicity. With the basicity ranging from 0.9 to 1.2, the melting temperature of slag increases rapidly, and the measured and calculated viscosity of slag presents a trend of an initial decrease followed by increase. When the basicity rising from 0.9 to 1.4, the diffraction peaks of pyroxene and feldspar in the slag climb to the high value and then start to fall, and the relative contents of perovskite and calcium-aluminum spinel gradually increase after an initial decrease. It is shown that the slag with basicity of 1.2 and viscosity of 0.130 Pa·s can present better performance.

Based on the technique for separation and recovery of metal ions in the leaching solution of spent lithium-ion batteries, nickel and cobalt ions were efficiently separated from manganese ions in leaching solution by selective precipitation of sulfide. The effects of pH value, addition coefficient of sodium sulfide, temperature and time for precipitation on the precipitation rates of nickel, cobalt and manganese ions were systematically investigated. The results show that the precipitation rates of nickel, cobalt, manganese and aluminum ions are 99.73%, 100%, 2.77% and 1.24%, respectively, after 6 min-precipitation at 25 ℃ with the addition of sodium sulfide at a coefficient of 1.5 and pH of 5.0. An orthogonal experiment shows that factors of addition coefficient of sodium sulfide, pH value, precipitation temperature and precipitation time have influence on the precipitation rates of nickel ions in a descending order, while the various factors of addition coefficient of sodium sulfide, precipitation temperature, pH value and precipitation time also have influence on the precipitation rates of cobalt ions in a descending order. It is found that the precipitation rates of manganese and aluminum can reach 99.77% and 6.86%, respectively, after a 12 min-precipitation at 70 ℃ with addition of sodium sulfide at a coefficient of 2.5 and pH of 6.0.

V₂O₅ thin films were prepared on FTO conductive glass substrates by electrodeposition-assisted sol-gel technique, and effects of precursor concentration on the structure, morphology and optical properties of V₂O₅ thin films were investigated. The results of XRD and XPS show that the prepared films are all V₂O₅ films, and the diffraction peaks in the XRD pattern are sharp, indicating that the films have good crystallinity. No other impurity peaks appeared in the XRD and XPS spectra, which indicated that the prepared V₂O₅ film had high purity. The results of SEM show that the surface of V₂O₅ film is uniform and compact, and mainly consists of spaced small particles. UV/VIS/NIR test results indicate that the transmittance of V₂O₅ thin film is greatly affected by the concentration of precursor, and reaches the highest of 80.18% when the concentration of precursor is 1∶100. The infrared spectrum test result shows that the infrared transmittance of V₂O₅ thin film decreases from 89.5% to 20.5%, as its semiconductor state at low temperature changes to metal state at high temperature.