A core of uranium deposit was taken in an experiment of column leaching with alkaline solution (NaHCO₃+H₂O₂), and then the surface characteristics and pore distribution of sandstone-type uranium deposit were analyzed by using scanning electron microscope images. The variation in the microscopic pore structure of uranium-bearing sandstone in alkaline in situ leaching process was characterized by using T₂ spectrum of nuclear magnetic resonance (NMR). The results show that the matrix in the core firstly becomes connected pores due to chemical dissolution of leaching solution, resulting in more pore throats among large and small pores. The Al(OH)₃ mineral colloid and CaCO₃ generated by the reaction are deposited intensively in the pores and microcracks, which reduces the effective reaction area between leaching solution and matrix, thus reducing the uranium leaching efficiency. During the period of 97-158 h, dissolution is predominant, leading to the amount of chemical dissolution much higher than the amount of precipitation and accumulation, thus forming a large number of connected pores. Further reaction and dissolution of uranium minerals in the leaching solution can increase the recovery of uranium mineral to the peak.

With a transport roadway at+392 m section of №92 ore body in Tongkeng Mine as an example, the testing area was firstly divided for investigating the required on-site data. Then, the roadway roof rock was scored by using mining rock mass rating (MRMR) system for rock quality classification and rating. Finally, an appropriate support measure was proposed for the roadway roof based on the grading result. It is shown that the roof rock mass has its score of 50 by RMR system and is rated to be Grade Ⅲ. However, with the modified MRMR system, the rock mass has its score of 29 and is rated to be Grade IV. Compared with the on-site actual investigation of structural plane, the rating result by using MRMR system is much more consistent with actual situation.

In order to study the energy distribution of blast wave propagation, the EEMD and Hilbert transform techniques were adopted to analyze the blast vibration signals at the same measuring point in different directions, on the same line with different distance away from explosion center, as well as with the same distance away from explosion center but with different maximum charges. It is found that vertical signal energy is mainly concentrated in the midbands, while the radial signal energy in horizontal direction is distributed in both the mid- and low-bands, and tangential signal energy in the horizontal direction is mainly concentrated in the high-bands. Under the same monitoring, a greater attenuation is found in high frequency energy and the proportion of signal energy distribution shifts from high-bands to low-bands as the distance is farther away from the explosion center. However, with the same distance away from the explosion center, increasing the maximum charge in a single stage can lead to higher proportion of low frequency energy, and significantly increased charge can bring more obvious effect.

Polycrystalline Cubic boron nitride (PCBN) composites were synthesized by adding a certain amount of Al and Ti, with TiN as the main binder. The effects of temperature (1 300-1 600 ℃) on the composition, microstructure and mechanical properties of the PCBN composites sintered with TiN-Al-Ti in combination with CBN were investigated. It is found that the phases of PCBN specimen are mainly composed of BN, TiB₂, TiN and AlN, and almost all Ti reacts with CBN in the sintering process to form TiN and TiB₂ phases. The relative density, flexural strength and hardness of PCBN are generally trending up with the rising of sintering temperature. And composite material with good comprehensive performance can be obtained at a sintering temperature of 1 500 ℃, showing its relative density of 99.1%, flexural strength of 807.8 MPa, fracture toughness of 6.2 MPa·m^1/2, and micro-hardness of 3 233HV.

In order to understand carbon performance of the mining sector in Hunan Province, the carbon emissions and carbon performance of the mining sector in Hunan Province were calculated based on the latest statistical data of national economic accounting, and factors influencing carbon performance were analyzed based on the established model. It is shown that the carbon performance of Hunan's mining sector was at a relatively low level from 2010 to 2020, and there was great difference in carbon performance of sub-sectors. Factors of asset size and energy efficiency had a positive impact on carbon performance, while factors of asset liability ratio and energy structure had negative constraints on carbon performance. Achieving economies of scale, improving energy efficiency, optimizing energy structure and maintaining a stable liabilities-to-assets ratio made sub-sectors of non-ferrous metal and gas production and supply in the front rank in terms of carbon performance. However, decreasing returns of scale in sub-sectors of coal mining and washing, as well as unreasonable energy structure and low energy efficiency in coal sub-sector led to the carbon performance of coal sub-sector ranking at the bottom. Consequently, it is suggested that the mining sector in Hunan Province should optimize its energy structure, accelerate low-carbon innovation, and increase various energy efficiency, so as to improve their carbon performance.

In order to improve the accuracy of flatness pattern recognition, a flatness pattern recognition method based on modified seagull optimization algorithm (MSOA) and Elman network is proposed. The weight threshold of Elman network is optimized with MSOA and then used for flatness pattern recognition. 20 sets of data are chosen for testing, and the obtained results are compared respectively with the flatness pattern recognition results based on BP neural network and traditional Elman network. It is found that algorithm method proposed in this paper has higher accuracy and better effect, with the mean square error lower than other algorithms by two orders of magnitude.

The progress in the research of micro-fine mineral flotation process is reviewed in terms of grinding, pulping, separation, and finally a prospect for the research direction of micro-fine mineral flotation process is presented.

For solving the problems of coarse feed size for grinding and high energy consumption in processing Daye Iron Ore, an experiment was carried out with high pressure roller grinding (HPRG) to mill the fine crushing products. The parameters of pressure between rollers, the water content of feed and the rotational speed at roller surface were optimized correspondingly as 10 MPa, 2% and 0.26 m/s. A closed-circuit test shows that HPRG can obviously reduce grinding energy consumption and improve mineral liberation degree. Jaw crushing and HPRG products were then taken as the feed for grinding-flotation test and it is shown that HPRG can improve flotation recovery, with recoveries of Cu, Fe and S all up by 2.56, 1.93 and 1.44 percentage points, respectively.

Aiming at the commercial production problems in the usage of high-temperature reagents for the reverse flotation in Qidashan Concentrator, a new laboratory-prepared combined collector (AG-1) was adopted in the reverse flotation of mixed magnetic concentrate at room temperature (20 ℃). The results show that a reverse flotation flowsheet consisting of one stage of roughing, one stage of cleaning and three stages of scavenging, with pulp pH of 11.5, the dosages for depressant (corn starch), activator (CaO) and collector (AG-1) at amount of 950 g/t.100 g/t and 750 g/t, respectively, can yield an iron concentrate grading 68.13% TFe at 88.43% recovery. XRD patterns and optical microscopy visualization of flotation concentrate and tailings show that AG-1 has good selectivity, and can effectively separate valuable minerals from gangue mineral of quartz. Compared with the single collector of sodium oleate or dodecylamine, AG-1 possesses a lower surface tension and a stronger ability in reducing the surface tension of gas-liquid interface, which can better improve mineral hydrophobicity.

The effect of rolling reduction on the microstructure, damping properties and mechanical properties of ZK60 magnesium alloy were studied. The results show that the damping properties of ZK60 magnesium alloy is improved with the increase of rolling reduction. When the strain amplitude is 0.01%, the Q^-1 value increases from 0.012 7 in as-cast state to 0.015 9 on rolling surface (RD-TD) with the rolling reduction of 50%, 0.020 4 on side section (RD-ND) and 0.018 3 on cross section (TD-ND). With the increase of rolling reduction, the (0002) basal texture strength of the alloy increases from 6.547 with the rolling reduction of 10% to 10.690 with the rolling reduction of 50%, which brings a certain impact to the damping properties of the alloy. The increased recrystallization volume fraction in the microstructure is the main influencing factor for the damping properties.