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The calcination process and the ratio of to calcium to silicon in raw materials are the key factors affecting the mineral composition and properties of natural water hard lime(NHL). This study prepared NHL was by different calcination processes using argillaceous limestone tailings with different chemical compositions as raw materials. This paper studied the mineral composition and compressive strength of the prepared NHL by a combination of orthogonal and single-factor tests, and analyzed the effect of calcination process and calcium-silica ratio on its performance. Results showed that: ① With the increase of calcination temperature, the content of CaO in NHL decreased, and the content of dicalcium silicate(Ca2SiO4, C2S)increased in NHL. ② Calcination temperature had the most significant effect on the mineral composition and compressive strength of NHL, followed by holding time and heating rate. ③ In the calcination temperature range of 1 000~1 100 ℃, the natural hydrostatic lime prepared by the given argillaceous limestone tailings meets the requirements of NHL2 and NHL3.5 strength grades. ④ When the calcium-silicon ratio is in the range of 3.55~6.76, the compressive strength of NHL decreases and then increases with the increase of calcium-silicon ratio, while the CaO content shows continuous increases.

An Al-based energetic micro-unit Al@PFPE@AP fuel powder with the oxidant AP coated on the surface of fluoride-modified Al powder was designed and prepared by the component composite technique to address the two major problems of incomplete combustion and component polarization of Al powder in solid propellants. The morphology, particle size, combustion properties and combustion products of the micro-unit powder were analyzed by scanning electron microscopy, laser particle size measurement, oxygen bomb calorimetry, inductively coupled plasma emission spectrometry and X-ray diffraction. The results show that the energetic microunits Al@PFPE@AP present a more obvious core-shell structure with uniform particle size, and when the addition amount of PFPE is 5%, the combustion heat value of Al@5%PFPE@AP is increased by 63.86%, the particle size of combustion products is decreased by 61.83%, and the active aluminum content of combustion products is decreased by more than 57% compared with the mechanically mixed AP+Al samples. Combustion mechanism analysis shows that PFPE can occur with Al powder pre-ignition reaction, increase the reaction activity of Al powder, and the surface of Al powder has a catalytic effect on the decomposition of AP, which reduces AP high temperature decomposition temperature and low temperature decomposition temperature were reduced by 12 ℃ and 10 ℃ respectively. The micro-unit structure has a significant contribution to the improvement of the combustion performance of the system and can substantially increase the energy performance of the important propellant components during combustion.

Based on the Internet of Things technology, obtaining the mine safety big data and making full use of the data are helpful to realize the forecast and early warning of mine safety situation. Taking the gas explosion accident as an example, by analyzing the cause of the accident, a mine safety situation evaluation index system is constructed, and each evaluation index is quantified. Based on the long and short-term memory(LSTM) network and the Bayesian network, a mine safety situation forecast model is proposed. According to the mine safety monitoring data, the mine safety situation evaluation index forecast values are obtained through the LSTM. The risk probability of mine safety accidents is inferred from Bayesian networks based on the evaluation index forecast values to obtain mine safety situation forecast. Based on the safety situation forecast results, an early warning mechanism is established. 4 warning levels and response departments are classified according to the warning situation, and corresponding early warning measures are established. An inversion of a gas explosion accident in a coal mine is used as an example, and the results show that the forecast results of mine safety situation based on LSTM and Bayesian network are consistent with the actual situation.

Livestock dung, discarded crop straws, and residual plastic film are the primary agricultural non-point sources of pollution. For livestock dung and discarded crop straw, the general treatment focuses on compost, animal fodder, industrial raw material, and new energy. The development of degradable mulch film is the main way to solve pollution from residual plastic film. However, an effective way to solve the above three types of pollution simultaneously and use them for ecological circular agriculture has been less studied. In this study, using cow dung and flax straw wastes as raw materials, we prepared natural, fibre-based paper mulch using the rapid-Kothen method and analysed the film-forming mechanism. Based on the Van Soest method, the cow dung and flax straw waste contain abundant cellulose fibres: 36.75% and 54.69%, respectively. The tensile strength and tear strength of fibre paper mulch are 1.87 kN/m and 19.91 N/mm, respectively. To enhance the adaptability of the fibre paper mulch in humid environments, the surface of the mulch was treated with alkyl ketene dimer (AKD). The AKD-coated fibre paper mulch displays hydrophobic properties, indicated by a contact angle of 128° ± 2°. It has a wet tensile strength of 0.64 kN/m and a wet tear strength of 8.23 N/mm. Additionally, it exhibits a dry tensile strength and a tear strength of 2.13 kN/m and 16.43 N/mm, respectively. Notably, the dry tensile strength is increased by 16.31%. In this way, the livestock dung and discarded crop straw can be reused, reducing dung pollution and straw burning in livestock farms, and the final products can alleviate the residual film pollution simultaneously. [ABSTRACT FROM AUTHOR]

Sodium sulfate (SS) is a neutral activator. SS-activated alkali-activated slag cement (AASC) has lower shrinkage. However, it sets slowly, and the mechanical property develops slowly. Slaked lime (SL) is an alkaline substance widely used in industry that can be used as an activator in AASC. In this paper, SL was used alone, and SL and SS were mixed together to prepare AASC. The effects of SL content on the setting time, shrinkage properties and mechanical strength of AASC were investigated. Furthermore, the mechanism was explored with the analysis of microscopic tests. The results showed that SS could not be used as an activator alone, while SL could be used as an activator alone, and SS could be combined with SL to prepare AASC. The setting time of the SL system or the SS-SL mix system decreased with the increase in SL. The mechanical properties of the SL system were poor. The SS-SL system showed the highest mechanical properties when SL was 3%. With the increase in SL, the autogenous and drying shrinkage of the SL system increased, while the former of the SS-SL system increased and the latter decreased. At the same time, due to the different changes in pore structure and mesoporous volume in the two systems, the drying shrinkage showed different changes. Compared with the SL system, ettringite (AFt) with a slight expansion property and more crystal phases were formed in the SS-SL system, which reduced the drying shrinkage. [ABSTRACT FROM AUTHOR]