Latest advances and progress in the microbubble flotation of fine minerals:Microbubble preparation,equipment,and applications

In the past few decades,microbubble flotation has been widely studied in the separation and beneficiation of fine minerals.Compared with conventional flotation,microbubble flotation has obvious advantages,such as high grade and recovery and low consumption of flotation reagents.This work systematically reviews the latest advances and research progress in the flotation of fine mineral particles by microbubbles.In general,microbubbles have small bubble size,large specific surface area,high surface energy,and good selectivity and can also easily be attached to the surface of hydrophobic particles or large bubbles,greatly reducing the detaching probability of particles from bubbles.Microbubbles can be prepared by pressurized aeration and dissolved air,electrolysis,ultrasonic cavitation,photocatalysis,solvent exchange,temperature difference method(TDM),and Venturi tube and membrane method.Correspondingly,equipment for fine-particle flotation is categorized as microbubble release flotation machine,centrifugal flotation column,packed flotation column,and magnetic flotation machine.In practice,microbubble flotation has been widely studied in the beneficiation of ultrafine coals,metallic minerals,and nonmetallic minerals and exhibited superiority over conventional flotation machines.Mechanisms underpinning the promotion of fine-particle flotation by nanobubbles include the agglomeration of fine particles,high stability of nanobubbles in aqueous solutions,and enhancement of particle hydrophobicity and flotation dynamics.

Numerical simulation of operation performance on production and injection of a double well geothermal system in Kailu Basin, Inner Mongolia

Inner Mongolia is abundant in geothermal resources,but the development and utilization of medium-depth geothermal resources for clean heating in winter is still in the preliminary stage compared with the neighboring provinces.In this paper,a recently developed geothermal heating system using the Mesozoic sandstone reservoirs in Baokang of Kailu Basin,Eastern Inner Mongolia was investigated,a threedimensional geological model of a pair of production and injection well was established,and numerical simulations on the long term operation performance were conducted and verified by pumping test and water level recovery test data.The effects of flow rates,the direction of wells,injection temperature and ratios on the flow field and water level in the thermal reservoir were analyzed.The results show that considering a 30-year operation period and a production rate from 90 m^(3)/h to 110 m^(3)/h,the optimum well spacing can be increased from 225 m to 245 m,with an average value of 235 m.With the decrease of the injection temperature,the cold front of the injection water has an increasing influence on the temperature in the production well.A complete injection or the principle of production according to injection is recommended in order to maintain the long-term operation stability.In addition,the location of the injection well should be arranged in the downstream of the natural flow field.The present results can provide a useful guide for the optimum design and performance prediction of geothermal wells,thus maintaining the production and injection balance and promoting the sustainable development and utilization of medium-depth and deep geothermal resources.

Pretreatment of copper-bearing refractory gold ores by bio-heap leaching

The refractory gold ores associated with rich copper and trapped in pyrite and quartz were studied. With conventional technique （all-sliming cyanidation）, the gold recovery rate is only 51.78%. To eliminate the negative effects of copper and pyrite on cyanidation and increase the gold recovery rate, the investigation on bio-heap leaching pretreatment was made, by which Cu would be dissolved and gold would be liberated from pyrite. The experiment adopted mixed bacteria, mainly ThiobaciUus ferrooxidan （named T.fl ）, as the bacterial catalyst for bio-preconditioning and was carried out in a PVC column with a diameter of 20 cm and a height of 1.3 m loaded with gold ores. The temperature was controlled between 28 and 30℃, the pH value was kept between 2.0-2.5, and the flux of sprinkling bacterial liquid was maintained 0.80 L/h. After 45-day＇s bio-oxidization, among the samples sizing from 0 to 5 mm, the oxidation rates of Cu, Fe and S were respectively 44.62%, 28.16% and 25.46%, and the gold recovery rate by cyaniding increased to 80.35%. The bio-heap leaching pretreatment can therefore effectively dissolve Cu and liberate gold from pyrite and lead to the increase of gold extraction.

Friction Shear Stress on the Surface of Iron-Based Coating/HSS during Sliding Wear of Pin Disk

With the increasing demand for lightweight and lower fuel consumption and safety of automobile industry, lightweight materials of high strength steel (HSS) are more and more widely used. The hot stamping technology, which is determined by the inherent mechanical properties of high strength steel, makes molds prone to wear failure in the harsh service environments. In this paper, a finite element model is proposed for analyzing the value and distributions law of friction shear stress of contact surface of the pin disk. Through the simulation process of sliding wear, two kinds of different cladding materials of the pin specimens including H13 and Fe65, were experimented under three different loads by using the software ABAQUS. And then the pin-on- disk wear test at elevated temperature was conducted to verify the effectiveness of the simula-tion results. The results showed that the friction shear stress of pin with iron-based cladding and H13 steel was different under different loads, but the distribution was basically the same;the normal friction shear stress increased gradually along the direction of the pin movement, and the tangential shear stress increased gradually from the center of the pin to the outside of the circle;the value of the friction shear stress of the normal joints on the contact surface was periodically fluctuating in the whole dynamic analysis step, while it was basically stable in the tangential direction.

lncRNA TUG1 regulates Smac/DIABLO expression by competitively inhibiting miR-29b and modulates the apoptosis of lens epithelial cells in age-related cataracts

Background:As one of the early discovered long non-coding RNAs(lncRNA),taurine upregulation gene 1(TUG1)has been widely expressed in a variety of tumors.Moreover,it promotes cell proliferation,differentiation,apoptosis,and migration.However,our understanding of its importance in the pathogenesis of cataracts remains limited.This study aimed to explore the mechanism by which lncRNA TUG1 mediates lens epithelial cell apoptosis in age-related cataracts(ARC)by regulating the microRNAs(miR-29b)/second mitochondria-derived activator of caspases axis,and to identify more non-surgical strategies for cataract treatment.Methods:The messenger RNA expression levels of TUG1,miR-29b,and Smac were detected using quantitative real-time polymerase chain reaction in vivo and in vitro.The expression of the Smac protein was analyzed by Western blotting and immunofluorescence.Flow cytometry and cell counting kit-8 assays were used to detect the cell apoptosis and proliferation rates,respectively.The targeted regulatory relationship between lncRNA TUG1,miR-29b,and Smac was verified by viral vector construction,co-transfection,nuclear and cytoplasmic separation,luciferase reporter assays,and RNA immunoprecipitation.Results:TUG1 and Smac were expressed at high levels in ARC and HLE-B3 cells treated with 200μmol/L H_(2)O_(2),whereas miR-29b expression was decreased.In vitro cell experiments confirmed that down-regulation of TUG1 could inhibit the apoptosis of lens epithelial cells.Mechanistically,Smac expression was negatively regulated by miR-29b.TUG1 competitively inhibited miR-29b expression and caused greater release of Smac.In addition,miR-29b partially reversed the effects of TUG1 on human lens epithelial cell line cells.Conclusions:lncRNA TUG1 increases Smac expression and promotes apoptosis of lens epithelial cells in ARC by competitively inhibiting miR-29b.This mechanism is the cytological basis for ARC formation.Based on these results,the lncRNA TUG1/miR29b/Smac axis may be a new molecular pathway that regulates ARC development.

Analysis of loss functions in support vector machines

Support vector machines(SVMs)are a kind of important machine learning methods generated by the cross interaction of statistical theory and optimization,and have been extensively applied into text categorization,disease diagnosis,face detection and so on.The loss function is the core research content of SVM,and its variational properties play an important role in the analysis of optimality conditions,the design of optimization algorithms,the representation of support vectors and the research of dual problems.This paper summarizes and analyzes the 0-1 loss function and its eighteen popular surrogate loss functions in SVM,and gives three variational properties of these loss functions:subdifferential,proximal operator and Fenchel conjugate,where the nine proximal operators and fifteen Fenchel conjugates are given by this paper.

A dynamic task assignment model for aviation emergency rescue based on multi-agent reinforcement learning

China's natural disaster situation presents a complex and severe scenario, resulting in substantial human and material losses as a result of large-scale emergencies. Recognizing the significance of aviation emergency rescue, the state provides strong support for its development. However, China's current aviation emergency rescue system is still under construction and encounters various challenges;one such challenge is to match the dynamically changing multi-point rescue demands with the limited availability of aircraft dispatch. We propose a dynamic task assignment model and a trainable model framework for aviation emergency rescue based on multi-agent reinforcement learning. Combined with a targeted design, the scheduling matching problem is transformed into a stochastic game process from the rescue location perspective. Subsequently, an optimized strategy model with high robustness can be obtained by solving the training framework. Comparative experiments demonstrate that the proposed model is able to achieve higher assignment benefits by considering the dynamic nature of rescue demands and the limited availability of rescue helicopter crews. Additionally, the model is able to achieve higher task assignment rates and average time satisfaction by assigning tasks in a more efficient and timely manner. The results suggest that the proposed dynamic task assignment model is a promising approach for improving the efficiency of aviation emergency rescue.

Extractant(2,3-dimethylbutyl)(2,4,40-trimethylpentyl) phosphinic acid(INET-3) impregnated onto XAD-16 and its extraction and separation performance for heavy rare earths from chloride media

（2,3-Dimethylbutyl）（2,4,40-trimethylpentyl）phosphinic acid（INET-3） was impregnated onto dry macroporous resins XAD-16 and pretreated XAD-16 with ethyl alcohol and HCl（Pre-XAD-16） to prepare the solvent impregnated resins SIRs-INET-3/XAD-16 and SIRs-INET-3/Pre-XAD-16. The molecular weight distribution of the low molecular weight（LMW） polymers washed off by ethyl alcohol during XAD-16 pretreatment was determined by gel permeation chromatography（GPC）. The macroporous resins（XAD-16 ＆ Pre-XAD-16）, the corresponding solvent impregnated resins（SIRs-INET-3/XAD-16 ＆SIRs-INET-3/Pre-XAD-16） and the PVA coated SIRs-INET-3/Pre-XAD-16 with boric acid as cross-linking agent were characterized by FT-IR, SEM-EDS and TGA. The effects of XAD-16 pretreatment and PVA coating technology on RE（III） adsorption equilibrium time, INET-3 losses during extraction and adsorption capacity were investigated. The adsorption kinetics, selectivity and stripping behaviors of SIRs-INET-3/XAD-16 were further studied. The washed off LMW polymers had the Mn of 36,656, Mw of 40,310 and polydispersity coefficient of 1.10. The SIRs-INET-3/XAD-16 had shorter equilibrium time,less INET-3 loss and more Tm（III） adsorption capacity than the SIRs-INET-3/Pre-XAD-16. The PVA coated SIRs-INET-3/Pre-XAD-16 had less INET-3 loss and more Tm（III） adsorption capacity but longer equilibrium time than the uncoated SIRs-INET-3/Pre-XAD-16. The adsorption of RE（III） on the SIRsINET-3/XAD-16 followed the pseudo-second-order kinetic model. The Tm（III） accumulative adsorption amounts onto SIRs-INET-3/XAD-16 after eight extraction stages was 23.6 mg/g. The separation factors of adjacent heavy RE（III） β（Er/Ho）, β（Tm/Er）, β（Yb/Tm） and β（Lu/Yb） values were 1.76, 2.59, 2.56 and 1.19,respectively. The adsorbed Lu（III） onto the SIRs-INET-3/XAD-16 can be stripped completely by 1.0 mol/L H2SO4.

Systematic degradation mechanism and pathways analysis of the immobilized bacteria:Permeability and biodegradation,kinetic and molecular simulation

In order to effectively improve the degradation rate of diesel,a systematic analysis of the degradation mechanism used by immobilized bacteria is necessary.In the present study,diesel degradation mechanisms were assessed by analyzing permeability,biodegradation,adsorption kinetics,and molecular simulation.We found that bacteria immobilized on cinnamon shells and peanut shells degraded relatively high amounts of diesel(69.94%and 64.41%,respectively).The primary degradation pathways used by immobilized bacteria included surface adsorption,internal uptake,and biodegradation.Surface adsorption was dominant in the early stage of degradation,whereas biodegradation was dominant in later stages.The diesel adsorption rate of the immobilized bacteria was in agreement with the pseudo second-order kinetic model.The immobilized bacteria and diesel interacted through hydrogen bonds.