Mechanism,prevention,and control of mining-induced dynamic disasters in underground metal mines in China:Challenges and solutions

Metal mineral resources play an indispensable role in the development of the national economy.Dynamic disasters in underground metal mines seriously threaten mining safety,which are major scientific and technological problems to be solved urgently.In this article,the occurrence status and grand challenges of some typical dynamic disasters involving roof falling,spalling,collapse,large deformation,rockburst,surface subsidence,and water inrush in metal mines in China are systematically presented,the characteristics of mining-induced dynamic disasters are analyzed,the examples of dynamic disasters occurring in some metal mines in China are summarized,the occurrence mechanism,monitoring and early warning methods,and prevention and control techniques of these disasters are highlighted,and some new opinions,suggestions,and solutions are proposed simultaneously.Moreover,some shortcomings in current disaster research are pointed out,and the direction of efforts to improve the prevention and control level of dynamic disasters in China’s metal mines in the future is prospected.The integration of forward-looking key innovative theories and technologies in the abovementioned aspects will greatly enhance the cognitive level of disaster prevention and mitigation in China’s metal mining industry and achieve a significant shift from passive disaster relief to active disaster prevention.

Molecular mechanisms of aflatoxin neurotoxicity and potential neuroprotective agents

Aflatoxins(AFTs)represent one of the most notorious classes of deadly mycotoxins produced by certain fungi that are found on agricultural crops.Aflatoxins are highly toxic to mammals and are known to cause a series of detrimental effects,including neuro-,hepato-,nephron-,and immuno-toxicity.In this original review we summarize the mechanisms of aflatoxin-induced neurotoxicity and the clinical potential of novel neuroprotective agents.Aflatoxin B1(AFB1)is the most toxic congener among the 21 identified AFTs.Recent studies have shown that food borne exposure to AFB1 and/or its metabolites often leads to fatal neurotoxicity in animals and humans.Animal studies indicated that AFB1 exposure could induce abnormal behavioral changes,including anxiety,lethargy disorders,depression-like behavior,cognitive,learning and memory defects,and decreased feeding behavior.Mechanistically,AFB1 exposure has been associated with lipid peroxidation,ablation of non-enzymatic and enzymatic antioxidant defense systems and decreased neurotransmitter levels.AFB1 exposure has also been shown to induce DNA damage,apoptosis,pyroptosis,and mitochondrial dysfunction in the brain tissue.Several signaling pathways,including gasdermin D,toll like receptor 2(TLR2),TLR4,Akt,NF-κB,ERK/MAPK,protein kinase C(PKC),and mitochondrial apoptotic pathways have been shown to participate in AFB1-induced neuronal or astrocyte cell death.Targeting these pathways by small molecules(e.g.,quercetin,curcumin,and gallic acid,and dimethyl fumarate),Chinese herbal extracts(e.g.,Artichoke leaf extract,Chelidonium majus ethanolic extract,pumpkin extract,and Crocus sativus L.tea),and probiotic supplements could effectively improve AFB1-induced neurobehavioral abnormalities and neurotoxicity.To date,the precise molecular mechanisms of AFB1-induced neurotoxicity and potential neuroprotective agents remain unclear.In the present review,the clinical manifestations,molecular mechanisms,and potential neuroprotective agents of AFB1-induced neurotoxicity are summarized in the broadest overview.It is most hopeful that this broad reaching review provides valuable insights and stimulates broader discussion to develop the effective neuroprotective agents against aflatoxins.

Research on the mechanism of rockburst induced by mined coal-rock linkage of sharply inclined coal seams

In recent years,the mining depth of steeply inclined coal seams in the Urumqi mining area has gradually increased.Local deformation of mining coal-rock results in frequent rockbursts.This has become a critical issue that affects the safe mining of deep,steeply inclined coal seams.In this work,we adopt a perspective centered on localized deformation in coal-rock mining and systematically combine theoretical analyses and extensive data mining of voluminous microseismic data.We describe a mechanical model for the urgently inclined mining of both the sandwiched rock pillar and the roof,explaining the mechanical response behavior of key disaster-prone zones within the deep working face,affected by the dynamics of deep mining.By exploring the spatial correlation inherent in extensive microseismic data,we delineate the“time-space”response relationship that governs the dynamic failure of coal-rock during the progression of the sharply inclined working face.The results disclose that(1)the distinctive coal-rock occurrence structure characterized by a“sandwiched rock pillar-B6 roof”constitutes the origin of rockburst in the southern mining area of the Wudong Coal Mine,with both elements presenting different degrees of deformation localization with increasing mining depth.(2)As mining depth increases,the bending deformation and energy accumulation within the rock pillar and roof show nonlinear acceleration.The localized deformation of deep,steeply inclined coal-rock engenders the spatial superposition of squeezing and prying effects in both the strike and dip directions,increasing the energy distribution disparity and stress asymmetry of the“sandwiched rock pillar-B3+6 coal seam-B6 roof”configuration.This makes worse the propensity for frequent dynamic disasters in the working face.(3)The developed high-energy distortion zone“inner-outer”control technology effectively reduces high stress concentration and energy distortion in the surrounding rock.After implementation,the average apparent resistivity in the rock pillar and B6 roof substantially increased by 430%and 300%,respectively,thus guaranteeing the safe and efficient development of steeply inclined coal seams.

Combustion mechanism and control approaches of underground coal fires:a review

With the large-scale mining of coal resources,the huge economic losses and environmental problems caused by underground coal fires have become increasingly prominent,and the research on the status quo and response strategies of underground coal fires is of great significance to accelerate the green prevention and control of coal fires,energy conservation and emission reduction.In this paper,we summarized and sorted out the research status of underground coal fires,focused on the theoretical and technical issues such as underground coal fire combustion mechanism,multiphysics coupling effect of coal fire combustion,fire prevention and extinguishing technology for underground coal fires,and beneficial utilization technology,and described the latest research progress of the prevention and control for underground coal fire hazards.Finally,the key research problems in the field of underground coal fire hazards prevention and control were proposed in the direction of the basic theory,technology research,comprehensive management and utilization,with a view to providing ideas and solutions for the management of underground coal fires.

Stabilization Mechanism of Calcium Lignosulphonate Used in Expansion Sensitive Soil

A series of tests were performed to investigate the macroscopic properties and the stabilization mechanism of calcium lignosulphonate modified expansive soil.Compared with natural soil,soil modified by 4%calcium lignosulphonate showed 56.5%increased 28 days unconfined compressive strength and 23.8%decreased free expansion rate.The X-ray diffraction analysis results indicate the existence of cation exchange and the reduction of montmorillonite interplanar spacing.The X-computed tomography results demonstrate that calcium lignosulphonate decreased the porosity and optimized the pore distribution.The calcium lignosulphonate also increased the stability of the suspension system according to the Zeta potential results.Moreover,the results of rheological tests show that the moderate amount of calcium lignosulphonate enhanced the yield stress and the plastic viscosity,proving the formation of a strong connection between soil particles.

Design and pricing of maintenance service contract based on Nash non-cooperative game approach

Nowadays manufacturers are facing fierce challenge.Apart from the products,providing customers with multiple maintenance options in the service contract becomes more popular,since it can help to improve customer satisfaction,and ultimately promote sales and maximize profit for the manufacturer.By considering the combinations of corrective maintenance and preventive maintenance,totally three types of maintenance service contracts are designed.Moreover,attractive incentive and penalty mechanisms are adopted in the contracts.On this basis,Nash non-cooperative game is applied to analyze the revenue for both the manufacturer and customers,and so as to optimize the pricing mechanism of maintenance service contract and achieve a win-win situation.Numerical experiments are conducted.The results show that by taking into account the incentive and penalty mechanisms,the revenue can be improved for both the customers and manufacturer.Moreover,with the increase of repair rate and improvement factor in the preventive maintenance,the revenue will increase gradually for both the parties.

Mechanism and Preventive Technology of the Thaumasite Form of Sulfate Attack on Cement Mortars

The deterioration mechanism of thaumasite towards cement or concrete structure and the deterioration pattern of in-situ construction caused by the formation of thaumasite were studied in this paper. To improve the TSA (the thaumasite form of sulfate attack) resistance, the cement type, water to cement ratios, the mineral admixture and the circumstance factors should be taken into consideration.

Cures for expansion shock and shock instability of Roe scheme based on momentum interpolation mechanism

The common defects of the Roe scheme are the non-physical expansion shock and shock instability. By removing the momentum interpolation mechanism(MIM), an improved method with several advantages has been presented to suppress the shock instability. However, it cannot prevent the expansion shock and is incompatible with the traditional curing method for expansion shock. To solve the problem, the traditional curing mechanism is analyzed. Effectiveness of the traditional curing method is discussed,and several defects are identified, one of which leads to incompatibility between curing shock instability and expansion shock. Consequently, an improved Roe scheme is proposed, which is with low computational costs, concise, easy to implement, and robust.More importantly, the proposed scheme can simultaneously solve the problem of shock instability and expansion shock without additional costs.

Research Progress of Polymer Fire Extinguishing Gel and Its Application in Forest Fire Prevention

The paper summarizes the structure and water-absorbing mechanism,classification,and preparation method of polymer fire extinguishing gel,and prospects for its application in aerial firefighting,forest ground fire extinguishing,opening of firebreaks,and mitigating human casualties in forest fire extinguishing.

Impact of Safety-Maintenance Practices on the Overall Performance of an Industry

The study aims to evaluate how safety-maintenance practices affect the mechanical engineering industry’s overall performance in Ghana. The study used a descriptive survey design technique to ascertain the type of maintenance engineering that was practiced in Ghanaian mechanical engineering workshops at the time of the study. In the mechanical engineering workshops, respondents provided both qualitative and quantitative data using a variety of data collecting instruments, with the quantitative approach being more common. The study employed Kumasi, Tamale, and Accra’s mechanical engineering workshops as a case study. The number of mechanical engineering workshop enterprises that made up the sample size for the questionnaire administration was sixty (60), chosen at random from the AGI membership registry. Primary data was gathered using interview guides and questionnaires. To analyse the data, descriptive statistics were employed. According to the study’s findings, mechanical engineering companies combined different maintenance techniques in order to best fit their organisational culture and equipment. Preventive shut-down, with a mean score of 4.78 and RII = 0.98, placing first (1st) in the Likert rating order, is the most frequently used maintenance system by respondents. The maintenance procedures employed by mechanical engineering organisations were influenced not only by their equipment and organisational culture but also by other factors such as cost, personnel expertise and external partnerships.

Injury rate,mechanism,and risk factors of hamstring strain injuries in sports:A review of the literature

Hamstring strains are one of most common sports injuries.The purpose of this literature review is to summarize studies on hamstring strain injury rate,mechanism,and risk factors in the last several decades with a focus on the prevention and rehabilitation of this injury.Hamstring injury commonly occurs in sporting events in which high speed sprinting and kicking are frequently performed,such as Australian football. English rugby,American football,and soccer.Basic science studies have demonstrated that a muscle strain injury occurs due to excessive strain in eccentric contraction instead of force,and that elongation speed and duration of activation before eccentric contraction affect the severity of the injury.Hamstring strain injury is likely to occur during the late swing phase and late stance phase of sprint running.Shortened optimum muscle length,lack of muscle flexibility,strength imbalance,insufficient warm-up,fatigue,lower back injury,poor lumbar posture,and increased muscle neural tension have been identified as modifiable risk factors while muscle compositions,age,race,and previous injuries are non-modifiable risk factors.The theoretical basis of some of these risk factors,however,is lacking,and the results of clinical studies on these risk factors are inconsistent.Future studies are needed to establish the cause-and-effect relationships between those proposed risk factors and the injury.

The influencing factors of urban land expansion in Changsha

This research systematically analyses land-use map of Changsha city in different periods of time. The spatial form and structural evolution was analysed by studying indices such as city land-use structure proportion, expansion intensity, economic flexibility, population flexibility, changing compactness index and so on. The dynamic mechanism of urban land expansion has been discussed by integrating the regional social economy development situation and many aspects such as the physiographical surrounding, population and economic development, traffic infrastructure, planning and regional development tactic and system innovation. The research indicates that the urban land expansion speed and intensity have steadily increased in Changsha from 1949 to 2004. The expansion form has been from a single external expansion to a combination form of external and internal expansion, from a circular or linear continuous form to a blocky or agglomeration shape. Overall, the urban land expansion of Changsha city is a phasic, diversified and complex process. And no matter what the stage is, it is an organic system containing multiple speed, pattern and shape, which are driven by multiple impetuses. The dominant feature at different stages was highlighted because of the balance and fluctuation between different forces, and the existing urban land border and shape have resulted from the joint efforts of these phasic forces.

Mechanisms of support failure and prevention measures under double-layer room mining gobs——A case study: Shigetai coal mine

In the practice of mining shallow buried ultra-close seams,support failure tends to occur during the process of longwall undermining beneath two layers of room mining goaf(TLRMG).In this paper,the factors causing support failure are summarized into geology and mining technology.Combining column lithology and composite beam theory,the key stratum of the rock strata is determined.A finite element numerical simulation is used to analyze the overlying load distribution rule of the main roof for different plane positions of the upper and lower room mining pillars.The tributary area theory(TAT)is adopted to analyze the vertical load distribution of each pillar,and dynamic models of coal pillar instability and main roof fracture are established.Through key block instability analysis,two critical moments are established,of which critical moment A has the greater dynamic load strength.Great economic losses and safety hazards are created by the dynamic load of the fracturing of the main roof.To reduce these negative effects,a method of pulling out supports is developed and two alternative measures for support failure prevention are proposed:reinforcing stope supports in conjunction with reducing mining height,or drilling ground holes to pre-split the main roof.Based on a comprehensive consideration of economic factors and the two categories of support failure causes,the method of reinforcing stope supports while reducing mining height was selected for use on the mining site.

Thermal expansion and mechanical properties of high reinforcement content SiC_(p)/Cu composites fabricated by squeeze casting technology

High reinforcement content SiCp/Cu composites (φp=50%, 55% and 60%) for electronic packaging applications were fabricated by patent cost-effective squeeze-casting technology. The composites appear to be free of pores, and the SiC particles are distribute uniformly in the composites. The mean linear coefficients of thermal expansion (CTEs, 20-100 ℃ ) of as-cast SiCp/Cu composites range from 8.8×10-6 ℃-1 to 9.9×10-6 ℃-1 and decrease with the increase of SiC content. The experimental CTEs of as-cast SiCp/Cu composites agree well with the predicted values based on Kerner model. The CTEs of composites reduce after annealing treatment due to the fact that the internal stress of the composite is released. The Brinell hardness increases from 272.3 to 313.2, and the modulus increases from 186 GPa to 210 GPa for the corresponding composites. The bending strength is larger than 374 MPa, but no obvious trend between bending strength and SiCp content is observed.

Microstructure and mechanical properties of AZ31 alloy prepared by cyclic expansion extrusion with asymmetrical extrusion cavity

The microstructure,texture evolution and mechanical properties of AZ31 magnesium alloy were investigated during the cyclic expansion extrusion with the asymmetrical extrusion cavity(CEE-AEC)process.The results show that continuous dynamic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX)occur during the CEE-AEC process.After 3 passes,the microstructures of the deformed samples are refined,and the average grain size of the alloys in asymmetrical cavity region is 6.9μm.The maximum intensities of the basal textures increase with the increase in the number of passes,and the basal textures are deflected during the deformation process.The basal texture of the alloys in asymmetrical cavity region is tilted by approximately±45°from the normal direction(ND)to the extrusion direction(ED).Grain refinement strengthening and texture deflection significantly improve the comprehensive mechanical properties of the deformed alloys.After 3 passes,tensile yield strength(TYS),ultimate tensile strength(UTS)and elongation-to-failure of the alloy in the asymmetric cavity region are 146 MPa,230 MPa and 29.7%,respectively.

Processing of AM60 magnesium alloy by hydrostatic cyclic expansion extrusion at elevated temperature as a new severe plastic deformation method

Hydrostatic cyclic expansion extrusion(HCEE) process at elevated temperatures is proposed as a method for processing less deformable materials such as magnesium and for producing long ultrafine-grained rods. In the HCEE process at elevated temperatures, high-pressure molten linear low-density polyethylene(LLDPE) was used as a fluid to eliminate frictional forces. To study the capability of the process,AM60 magnesium rods were processed and the properties were investigated. The mechanical properties were found to improve significantly after the HCEE process. The yield and ultimate strengths increased from initial values of 138 and 221 MPa to 212 and 317 MPa, respectively.Moreover, the elongation was enhanced due to the refined grains and the existence of high hydrostatic pressure. Furthermore, the microhardness was increased from HV 55.0 to HV 72.5. The microstructural analysis revealed that ultrafine-grained structure could be produced by the HCEE process. Moreover, the size of the particles decreased, and these particles thoroughly scattered between the grains. Finite element analysis showed that the HCEE was independent of the length of the sample, which makes the process suitable for industrial applications.

Urban Agglomeration Formation and Its Spatiotemporal Expansion Process in China: From the Perspective of Industrial Evolution

Urban agglomeration research has received increasing attention in China’s national development strategies, and has become a hot topic in academic research. This study develops a theoretical framework that explores the formation mechanism and expansion process of urban agglomerations from the perspective of industrial evolution, and identifies the development issues and their causes by taking Yangtze Delta and Beijing-Tianjin-Hebei urban agglomerations as case studies. In the process of urban agglomeration formation within a free market, as has happened in Yangtze Delta region, the central city develops first, its secondary industry is then transferred to its neighboring cities, and the work division and cooperation with the neighboring cities is gradually established. However, in the 1990 s, aiming to become an international metropolis, Beijing implemented a series of administrative policies to encourage the reduction of the secondary industry and the development of the tertiary industry, before its secondary industry were fully developed and transferred to its neighboring cities. This delayed the integration process and the development of the Beijing-Tianjin-Hebei urban agglomeration. This study builds a good foundation for the construction of the theoretical system’s urban agglomeration study, and provides references for decision making in an urban agglomeration development.

The Mechanism of Ground Granulated Blastfurnace Slag Preventing Alkali Aggregate Reaction

Three different methods were applied to study the alkali content of gelpores in cement. In the closed system, the concentration of K＋, Na＋ and OH - have not reduced with the increase of age. In the open system, the diffusion and transferring of K＋ and Na＋ towards free space leads to the de-crease of total alkali content. In the micro-analysis system, the contents of K＋ and Na＋ in the first hy- drated layer of ground granulated blastfurnace slag （GBFS） are very low, while the contents of calcium and magnesium are relatively high. This phenomenon shows that the mechanism of GBFS preventing alkali aggregate reaction （AAR） is： when GBFS is dissolved by alkali medium, SiO2 and Al2O3 are dissolved into the cement matrix, then around GBFS particles form reaction rings rich in Ca2＋ and Mg^2＋, and the C-S-H gel of positive charges formed in the area repulses K＋ and Na＋, which are forced to transfer to the mortar＇s matrix, pore or mortar sample surface. The transferred K ^＋ and Na^＋ form alkali gel products with other dissolved ions, then become evenly distributed in the mortar sample and react with Ca（OH）2 in pore solutions to form （Na,K）x-2z·zCa·（SiO2）y·（OH）x gel products; and thus changes the AAR gel products＇ structure. The gel products will not expand, and so they can delay expansion destruction.

Effect of Dietary Resistant Starch on Prevention and Treatment of Obesity-related Diseases and Its Possible Mechanisms

Overweight or obesity has become a serious public health problem in the world, scientists are concentrating their efforts on exploring novel ways to treat obesity. Nowadays, the availabilities of bariatric surgery and pharmacotherapy have enhanced obesity treatment, but it should has support from diet, physical exercise and lifestyle modification, especially the functional food. Resistant starch, an indigestible starch, has been studied for years for its beneficial effects on regulating blood glucose level and lipid metabolism. The aim of this review is to summarize the effect of resistant starch on weight loss and the possible mechanisms. According to numerous previous studies it could be concluded that resistant starch can reduce fat accumulation, enhance insulin sensitivity, regulate blood glucose level and lipid metabolism. Recent investigations have focused on the possible associations between resistant starch and incretins as well as gut microbiota. Resistant starch seems to be a promising dietary fiber for the prevention or treatment of obesity and its related diseases.

Dimethylacetamide-induced Hepatic Injury in Vitro: Mechanism and Potential Preventive Strategy

N,N-Dimethylacetamide （DMAc） is a widely used organic solvent in modern chemical industry with low to moderate hepatotoxicity to occupational health of employees. But so far, there are fewer and less conclusive data concerning its pathogenic mechanism in detail. In current study, the toxicity of DMAc was firstly investigated on human normal hepatocytes （LO-2）, using a series of molecular biology measurements to ananlyze the effect and mechanism of DMAc-induced hepatic cell injury and explore effective prophylactic measures. We found that DMAc triggered LO-2 apoptosis in a obviously dose-dependent manner, caused by increased ROS generation and activation of Bcl-2 pathway. Significantly, glutathione （GSH） rather than vitamin C （Vit C） could partially inhibit DMAc-induced apoptosis thus showing potential as a effective precaution for workers.