Search

As a new type of mine geological disaster, water-sand inrush has the characteristics of concealment, sudden onset, difficulty in monitoring, and strong destruction. Therefore, exploring the characteristics of overlying rock mining degradation and the disaster mechanism of water-sand inrush has guiding significance for the prevention and control of loose layer water hazard. Firstly, the influence mechanism of different material proportioning on the strength and permeability characteristics of similar materials is studied through similar material proportioning and testing experiments, and a new solid-fluid coupling similar material suitable for simulating soft rock layers is developed. Then, by using the test system for water-sand inrush, similar simulation tests are conducted for mining under the condition of a single water-bearing structure capping thin and medium thick bedrock, and a double layered structure capping thin bedrock. The characteristics of mining crack and the disaster mechanism of water-sand inrush under the above strata structure conditions are analyzed. The test results show that the new solid-fluid coupling similar material has the characteristics of water resistance, anti disintegration, anti softening, low permeability, low strength, and low plasticity, and the permeability coefficient decreases exponentially with the increase of calcium carbonate content, while the uniaxial compressive strength exhibits a quadratic polynomial growth characteristic. The first weighting stage and the first periodic weighting stage of mining shallow and thin bedrock are easy to induce water-sand inrush. The mining cracks present an “OX” distribution on the plane, and as the thickness of bedrock and the clay layer at the bottom of the loose layer increases, the bedrock gradually transforms from tensile shear failure to tensile failure, and the morphology of the cracks also changes. At the same time, the opening and smoothness of cracks are reduced, which can reduce the inducing risk and harm degree of water-sand inrush. The ratio of crack opening to sand particle size , as well as the smoothness of crack, are the key factors determining the occurrence and severity of water-sand inrush.

The ecological implications of deep-sea mining, particularly the considerable discharge of suspended sediments during operational processes, have attracted substantial concerns. In order to reveal the metal regeneration dynamics in the polymetallic nodule area of the western Pacific Ocean, ex-situ sediment disturbance experiments were conducted on a research vessel. After two levels of regulated stirring disturbance were exerted for half an hour, the concentrations of 12 dissolved metals and physicochemical parameters, including Eh and pH, were monitored continuously in the overlying water for three days. Porewater samples were also collected at the starting and ending time of each experiment to detect the change of dissolved metal profiles within the sediments. The findings revealed that the sediment disturbance led to fluctuations in the concentrations of metals in the overlying water, with manganese exhibiting the most pronounced change at a coefficient of 208%. The temporal patterns of dissolved metal concentrations demonstrated a coherent behavior among certain metals, such as Li, V, Co, Ni, Rb, Mo, and Cs, which displayed an overall increase, ultimately surpassing the initial concentrations in the overlying water. In line with this, the metal concentration profiles in the porewater were also elevated. Spearman correlation analysis confirmed the synchronized behavior of these metals. The results suggested that the metals mobility might be governed by physicochemical factors in the overlying water. Moreover, the sedimentary features, such as grain size composition, and the morphological state of metals in sediments played pivotal roles in the differential responses of metal groups to sediment disturbance across stations. Conversely, the disturbance intensity was found to have a relatively minor impact on the dissolved metal behavior. The findings from the ex-situ experiments provided critical insights for predicting metal regeneration related to deep-sea mining, which are expected to be validated through rigorous monitoring protocols during future in-situ mining trials.

Abstract Water inrush originating from hidden faults in the coal seam floor is challenging to prevent due to their concealed nature. This paper develops a coupled stress–seepage–damage model for simulating rock fracture, implemented using the finite element method. The model is validated against compression-seepage tests on rock samples, capturing realistic dynamics of shear and tensile damage as well as permeability. The model is applied to the 27305 working face of a coal mine in Shandong Province, China, revealing the evolution of water inrush caused by a hidden fault. The results indicate that as the working face progresses, both the floor damage and the internal damage within the hidden fault escalate gradually. When mining reaches 80 m, the hidden fault has been activated internally, and the depth of floor damage reaches 13 m, which still has a certain distance from the hidden fault. At 100 m, the depth of the floor damage has stabilized, while the stress concentration at the hidden fault's tip increases, and it begins to expand if conditions for tensile damage are met. By the time mining reaches 110 m, the hidden fault has expanded 9.2 m in length and connected with the floor damage zone, forming a water inrush channel that links the aquifer to the working face, presenting a significant water inrush risk. This work provides an intuitive approach to understanding the evolution of water inrush from a hidden fault, aiding in the prevention of water inrush disasters in practical engineering applications.

In response to the current challenges of high water pressure and easy conduction in kilometer deep wells, we propose the “hydrophobic pressure reduction, slurry reinforcement” mine water control technology, which requires slurry materials with “high strength, strong stability, easy flow, low cost” and other properties. “High strength” can be achieved by adding nano-reinforced materials. “Strong stability” can be achieved by preferentially selecting easy-to-consolidate and difficult-to-disperse raw materials and adjusting the mixing conditions. “Stable flow” can be achieved by adjusting the particle size of added raw materials and increasing the interfacial friction. “Low cost” can be achieved by using existing large-scale industrial and mining solid waste products that are in urgent need of treatment, supplemented by a small amount of additives. In view of the above problems, this paper aims at reinforcing the coal seam floor with slurry, and takes the large-scale utilization of industrial and mining wastes as the direction. By using waste tire rubber particles, fly ash and clay as the main materials, supplemented with a small amount of admixtures, the orthogonal test method is used to carry out experimental research on the basic performance of solid waste slurry filling materials. The effects of different rubber particle admixtures and admixtures were analyzed in the paper, and their effects on the flowability, mechanical properties, stability in mine water environment, impermeability and microstructural properties of the grouted stone body were derived. The research results show that when rubber particles are mixed with 20%, fly ash with 65%, clay with 15%, and nano-silica with 1% of solid powder, the flow of the grouted slurry is 293 mm, the 28 d compressive strength of the grouted stone body is 11.7 MPa, and the seepage pressure of the stone body is 0.8 MPa, and the obtained test results can meet the demand of field grouting reinforcement, which is useful for The obtained test results can meet the demand for on-site grouting reinforcement, which has scientific reference value for large-scale bottom slab fracture grouting reinforcement and also provides reference for large-scale utilization of solid waste products.

Summary: Peroxymonosulfate (PMS)-based advanced oxidation processes in liquid phase systems can actively degrade toluene. In this work, the catechol structural surfactant was introduced to synthesize the dispersed and homogeneous CoFe2O4 nanospheres and embedded into MoS2 nanoflowers to form magnetically separable heterojunction catalysts. The innovative approach effectively mitigated the traditionally low reduction efficiency of transition metal ions during the heterogeneous activation process. In CoFe2O4/MoS2/PMS system, the toluene removal efficiency remained 95% within 2 h. The contribution of SO4⋅-, ·O2−, ·OH, and 1O2 was revealed by radical quenching experiment and electron paramagnetic resonance spectroscopy. The results illustrated that MoS2 offers ample reduction sites for facilitating PMS activation via Fe3+/Fe2+ redox interactions. Furthermore, an investigation into the toluene degradation pathway within the CoFe2O4/MoS2/PMS system revealed its capability to suppress the formation of toxic byproducts. This ambient-temperature liquid-phase method presented promising route for the removal of industrial volatile organic pollutants.

Abstract We have investigated the activation characteristics of mining faults and the effect of grouting reinforcement under thick loose layer and thin bedrock of the working face and evaluate their impact on the safety of mining at similar working faces. Implementing the geological conditions of the 331 working face of the Yangcun Coal Mine (China) of the Yankuang Energy Group Corporation, we have analyzed mechanically the process of fault activation at first. Subsequently, we have obtained the mechanical criterion of fault slip and the expression of relative strength of the nearby rock mass. Using numerical software we have simulated and analyzed the damage characteristics of different bedrock thicknesses on overlying rocks and faults in the fluid–solid coupling mode. In addition, we have studied the controlling effect of grouting reinforcement on fault activation, which has been verified in the field. The main results of our study show that: 1. The mechanical properties of the rock mass near the fault interface have changed and they are related to the cohesive force of the interface; 2. The water inrush mode of the working face changes under different bedrock thickness, and the thinner the bedrock, the less easily the fault is destroyed 3. The slip of the high-level fault is reduced after the grouting of the fault, the propagation of the fracture zone at the fault is suppressed, the seepage of the aquifer water is prevented, and the safe recovery is realized. The results of our study provide a scientific basis for the secure mining across the fault of the 331 working face of Yangcun Coal Mine. Based on the results of our study the working face can be mined safely from now on and in the future.

As a promising choice of new-generation green propellant fuels, hypergolic ionic liquids (HILs) have attracted a great deal of interest in recent ten years, illustrated by their applications in the field of space science and exploring outer space. The design and syntheses of new ionic liquids (ILs) are the basis of the HILs’ sustainable development. In the recent years, many new HILs have been created through the rational design, and their hypergolic property and applications have been studied extensively. With the aim of familiarizing the reader with new trends in the area of HILs research, in this review we present the latest developments of new HILs including syntheses, properties, structure-property relationship and their applications in the field of liquid bipropellants, while the debatable issues and future challenges that need to be addressed are also discussed. Through this review, we intend that more readers may learn about the newest trends in the field of ionic liquid propellants, and it may also provide an additional catalyst for the vigorous development of new-generation green space propellants.

The Bohai Sea is a semi-enclosed shallow water that is influenced by both natural and anthropogenic stressors. However, the microeukaryotic communities and environmental factors that affect them in different regions remain largely unclear. We investigated microeukaryotic communities in surface sediments from five geographic regions using high-throughput sequencing of the 18S rDNA gene. The Miaodao Archipelago, Yellow River Estuary, and Central Bohai Sea had the highest Shannon and Simpson indices of the eukaryotic communities, while the Yellow River Estuary exhibited the highest Chao1 index. The microeukaryotic communities in surface sediments were mainly composed of Dinoflagellata, Bacillariophyta, Ciliophora, Cercozoa, and Protalveolata. Thalassiosira has a relatively high abundance at the Liaodong Bay and Central Bohai Sea, possessing the proportion of 41.70% and 38.10%, respectively, while Gonyaulax was the most abundant taxa in the Bohai Bay, occupying a proportion of 57.77%. Moreover, a negative correlation between diatoms and dinoflagellates was observed. Phosphorus, nitrogen, salinity, temperature, and silicate were major environmental determinants of microeukaryotic composition. Microeukaryotic communities in the surface sediments, especially for the composition and ratio of diatoms to dinoflagellates, reflected the environmental quality of marine ecosystems. Overall, these microeukaryotic community compositions provide a reliable indicator for monitoring the level of marine eutrophication in the Bohai Sea.

Cadmium (Cd) pollution has become a global issue due to industrial and agricultural developments. However, the molecular mechanism of Cd-induced detrimental effects and relevant signal transduction/metabolic networks are largely unknown in marine fishes. Here, greenfin horse-faced filefish (Thamnaconus septentrionalis) were exposed to 5.0 mg/L Cd up to 7 days. We applied both biochemical methods and multi-omics techniques to investigate how the gills respond to Cd exposure. Our findings revealed that Cd exposure caused the formation of reactive oxygen species (ROS), which in turn activated the MAPK and apoptotic pathways to alleviate oxidative stress and cell damage. Glycolysis, protein degradation, as well as fatty acid metabolism might assist to meet the requirements of nutrition and energy under Cd stress. We also found that long-term (7 days, “long-term” means compared to 12 and 48 h) Cd exposure caused the accumulation of succinate, which would in turn trigger an inflammatory response and start an immunological process. Moreover, ferroptosis might induce inflammation. Overall, Cd exposure caused oxidative stress, energy metabolism disturbance, and immune response in greenfin horse-faced filefish. Our conclusions can be used as references for safety risk assessment of Cd to marine economic fishes.

The soft coral order Alcyonacea is a common coral found in the deep sea and plays a crucial role in the deep-sea ecosystem. This study aims to predict the distribution of Alcyonacea in the western Pacific Ocean using four machine learning-based species distribution models. The performance of these models is also evaluated. The results indicate a high consistency among the prediction results of the different models. The soft coral order is primarily distributed in the Thousand Islands Basin, Japan Trench, and Thousand Islands Trench. Water depth and silicate content are identified as important environmental factors influencing the distribution of Alcyonacea. The RF, Maxent, and XGBoost models demonstrate high accuracies, with the RF model exhibiting the highest prediction accuracy. However, the Maxent model outperforms the other three models in data processing. Developing a high-resolution, high-accuracy, and high-precision habitat suitability model for soft corals can provide a scientific basis and reference for China’s exploration and research in the deep sea field and aid in the planning of protected areas in the high seas.

Confined water inrush caused by fault activation is the main form of water disaster in deep mining. With theoretical analysis and similar simulation tests, the mechanism and evolution law of delayed water inrush caused by fault activation are revealed. At the theoretical level, the expansion and extension of the internal microstructure in the fault zone under the action of the mining stress field and seepage field are the essential causes of fault activation. Overlying strata movement and surrounding rock creep failure are the basic reasons for delayed water inrush caused by fault activation, and delayed time caused by surrounding rock creep failure is much longer than that of overlying strata movement. A similar simulation test was carried out with self-development solid–liquid coupling with similar simulation materials; the results show that delayed water inrush caused by fault activation with mining includes three stages. Micro-activation stage: Water inrush weakness point is formed because of the expansion and extension of the micro-fissure and structure at the bottom of the fault zone. Macro-activation stage: With the change in the stress of the waterproof coal pillar and surrounding rock, the micro-fissures and structures in the stress relief area and tension area of the fault zone expand and extend sharply; meanwhile, water intrudes into the interlayer stratification of the floor in the stress relief area, forming a strong laminar flow phenomenon, and cracks in the floor form and expand; finally, water-conducting channels in the fault zone and floor are formed. Water inrush stage: The waterproof coal pillar and water-resisting layer fail and are destroyed, and the first confined water inrush point is located at the junction of the waterproof coal pillar and gob floor.

Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental pollutants that pose a threat to human health. Among these PAHs, benzo[a]pyrene (BaP), a five-ring compound, exhibits high resistance to biodegradation. White-rot fungus Phlebia acerina S-LWZ20190614-6 has demonstrated higher BaP degradation capabilities compared with Phanerochaete chrysosporium and P. sordida YK-624, achieving a degradation rate of 57.7% after 32 days of incubation under a ligninolytic condition. To further enhance the biodegradation rate, three nonionic surfactants were used, and the addition of 1 or 2 g·L−1 of polyethylene glycol monododecyl ether (Brij 30) resulted in nearly complete BaP biodegradation by P. acerina S-LWZ20190614-6. Interestingly, Brij 30 did not significantly affect the activity of manganese peroxidase and lignin peroxidase, but it did decrease laccase activity. Furthermore, the impact of cytochrome P450 on BaP degradation by P. acerina S-LWZ20190614-6 was found to be relatively mild. Transcriptomic analysis provided insights into the degradation mechanism of BaP, revealing the involvement of genes related to energy production and the synthesis of active enzymes crucial for BaP degradation. The addition of Brij 30 significantly upregulated various transferase and binding protein genes in P. acerina S-LWZ20190614-6. Hence, the bioremediation potential of BaP by the white-rot fungus P. acerina S-LWZ20190614-6 holds promise and warrants further exploration.

Many deep mining mines in southwestern Shandong Province of China are covered with thick loose layers. When mining near the loose layers, there is a risk of water and sand inrush, which threatens the personal safety of miners. The prediction of sudden water and sand inrush is difficult due to the comprehensive influence of many factors, and the influencing factors are fuzzy and random. To solve this problem, in this paper, a new risk assessment method of water and sand inrush based on comprehensive weight and cloud model was proposed. Seven factors are selected as indexes: the aquifer thickness, the thickness ratio of sand layer to clay layer, the thickness of bottom clay layer, the coal seam thickness, the percentage of core recovery, the geological structure, and the bedrock thickness. The assessment index system is established, and the index is divided into three grades. A comprehensive weighting method, which combines analytic hierarchy process (AHP), entropy weight method (EWM), and minimum entropy principle, is used to reasonably assign the weight of index. Based on the cloud generator equation, the membership function is obtained. The assessment result of the assessment object is obtained by combining the membership degree and the weight of index. The comprehensive weight-cloud model assessment method is applied to the risk assessment of water and sand inrush in the 6311-2 working face in the sixth mining area of Baodian Coal Mine. According to the assessment results, the following conclusions can be drawn: (1) the bedrock thickness and the coal seam thickness are the main factors of water and sand inrush under loose layer mining; (2) the assessment results obtained by the comprehensive weight-cloud model method are consistent with the actual situation. The assessment method can provide scientific reference for the safe mining under the thick loose layer in the deep mines of southwest Shandong.

For decades, neuromodulation technology has demonstrated tremendous potential in the treatment of neuropsychiatric disorders. However, challenges such as being less intrusive, more concentrated, using less energy, and better public acceptance, must be considered. Several novel and optimized methods are thus urgently desiderated to overcome these barriers. In specific, temporally interfering (TI) electrical stimulation was pioneered in 2017, which used a low-frequency envelope waveform, generated by the superposition of two high-frequency sinusoidal currents of slightly different frequency, to stimulate specific targets inside the brain. TI electrical stimulation holds the advantages of both spatial targeting and non-invasive character. The ability to activate deep pathogenic targets without surgery is intriguing, and it is expected to be employed to treat some neurological or psychiatric disorders. Recently, efforts have been undertaken to investigate the stimulation qualities and translation application of TI electrical stimulation via computational modeling and animal experiments. This review detailed the most recent scientific developments in the field of TI electrical stimulation, with the goal of serving as a reference for future research.

Because agricultural wastes can be used as good building insulation materials due to their huge output, wide distribution, recyclability, and high thermal resistance, they are the better selections to improve the thermal performance of envelopes in rural buildings. The hollow bricks filled-with agricultural wastes were proposed, and six groups of walls were built by hollow bricks filled with different kinds of agricultural wastes, including reed leaves, reed stems, rice shells, rice straws, and wheat stems in order to select the reasonable agricultural wastes. The simple hot-box heat flow meter method was used to measure and calculate the overall heat transfer coefficient of hollow brick walls filled with agricultural wastes. The experimental results showed that the insulation performance of the hollow brick was significantly improved due to filling agricultural wastes. Five agricultural wastes can reduce the overall heat transfer coefficient of hollow-brick walls by 12.7~32.7%. And the rice straws were the best selection to be filled into hollow bricks and they can reduce the overall heat transfer coefficient from 1.59 W/(K·m2) to 1.07 W/(K·m2), which showed that thermal performance of hollow-brick wall was improved by 32.7%. Hollow bricks filled with agricultural wastes can be utilized for future construction renovation in rural areas as insulation materials.

In this paper, a grouting material with low cost and high density was proposed for the reinforcement of large-scale floor cracks. The component screening test, mechanical property test, rheological properties test, and impermeability test were conducted to obtain the strength, rheological properties, and permeability of the new grouting materials. In order to fully understand the physicochemical properties of the new grouting material, a total of 12 sets of test pieces were produced using cement, clay, and fly ash as the main body, and foaming agent as the auxiliary material. Each set of the test pieces had different proportions of ingredients, pores conditions, and auxiliary chemical materials (water reducing agents, defoamers). The test results showed that: (1) The optimal proportion of ingredients for the new grouting material (including 1% foaming agent) was: 40% of cement, 30% of clay, and 30% of fly ash. (2) The optimal amount of fly ash for the new grouting material was 30% and the optimal foaming amount for the new grouting material was 1%. The impermeability of the grouting material was 0.7 MPa, which reached Level P6. The new grouting material was suitable for the HB rheology model. (3) The pores were uniformly distributed inside the solidified body of the new grouting material. In the later stage, the strength of the solidified body was stable, and the flow loss was reduced. At present, the corresponding proportion of ingredients and the performance parameters of the new grouting material were tested in the laboratory. In the future, it is necessary to further determine the effect of the grouting material in the reinforcement of the floor crack of the coal seam and to improve the proportion of ingredients for the grouting material in the mine sites. Keywords: Grouting material, Coal mine solid waste, Floor crack, Grouting reinforcement, Experimental study

The search for environmentally friendly, lead-free primary explosives continues to be important for both military and civil applications. Here the authors synthesize an organic fused-ring initiating substance that possesses many of the attributes necessary for commercial application.

The coal mine accidents seriously affect the safety and efficiency of mining for coal mining enterprises. The reliable emergency rescue (ER) processes are explored to minimize the loss of accidents. This paper introduces the stochastic Petri net (SPN) and Markov chain (MC) models based on the system structure flow to analyze the ER processes of coal mine accidents. In addition, a triangle fuzzy strategy is presented to optimize the SPN model. The “9·28” major water inrush accident in Shanxi Fenxi Zhengsheng Coal Company of China is adopted to evaluate the time performance and accident data of the ER process. The MC model-based steady-state probabilities of the system under various states are used to calculate the average delay time of this system. The triangular fuzzy strategy is used to analyze the change value of the total time in the ER system at the unit transition speed when the firing rate of each transition is changed, which finds the most time-consuming key activities in the ER process. The results show that SPN and MC can reflect the dynamic behaviors of ER process, which provides a reference for the rescue operations of other coal mine accidents. The triangular fuzzy strategy can quickly find out the key activities affecting the ER time, which greatly decreases the calculations generated by analyzing the total time of the system changed at the unit transition speed.

High-pressure submerged cavitation jet is widely used in the fields of material peening, petroleum drilling, and ocean engineering. The impact performance of the jet with intensive cavitation is related to the factors such as working condition and the nozzle geometry. To reveal the relationship between the nozzle divergent angle and the jet pressure on the unsteady characteristics of the jet, high-speed photography with frame rate of 20000 fps is used to record the image of the cavitation clouds. Grayscale analysis algorithm developed in MATLAB is used to study the effects of injecting condition on the special structure, unsteady characteristics, and shedding frequency of the cavitation bubbles. The impact load characteristics of the cavitation jet with different cavitation numbers and stand-off distances are recorded using a high-response pressure transducer. It is found that the cavitation number is the main factor affecting the cavitation morphology of the submerged jet. The lower the cavitation number is, the more intense the cavitation occurs. The outlet divergent angle of the convergent-divergent nozzle also has a significant influence on the development of the cavitation clouds. In the three nozzles with the outlet divergent angles of 40°, 80°, and 120°, the highest bubble concentration is formed usinga nozzle with a divergent angle of 40°, but the high-concentration cavitating bubbles are only distributed in a very small range of the nozzle outlet. The cavities generated by using the nozzle with a divergent angle of 80° can achieve good results in terms of concentration and distribution range, while the nozzle with divergent angle of 120° has lower cavitation performance due to the lack of the constraint at the outlet which intensifies the shear stress of the jet. According to the result of frame difference method (FDM) analysis, the jet cavitation is mainly formed in the vortex structure generated by the shearing layer at the nozzle exit, and the most severe region in the collapse stage is the rear end of the downstream segment after the bubble cloud sheds off. The impact load of the cavitation jet is mainly affected by the stand-off distance of the nozzle from the impinged target, while the nozzle outlet geometry also has an effect on the impact performance. Optimizing the stand-off distance and the outlet geometry of the nozzles is found to be a good way to improve the performance of the cavitation jet.

Based on the coal seam mining under the condition of thick soil layer, the mechanical mining subsidence process under the condition of thick soil layer was analyzed. Combined with the results of core drilling and laboratory test in the mining area, the mechanical analysis of the special transition strata of “hard soil-soft rock” at the bottom of the soil layer was carried out. Additionally, the characteristics of the shallow buried soil layer were compared and analyzed. Furthermore, the significance of this transitional font to the surface subsidence law was proposed. By using the numerical simulation software of FLAC3D and choosing the thickness of “hard soil-soft rock” transitional font as the influencing factor, a model was established and the surface subsidence characteristics of different stratum combinations were numerically simulated. The research results show that the transitional font is the special strata indicating that the hard soil is transiting to the soft rock, having a significant effect on the ground movement and deformation induced by coal mining. It cannot be designated into the loose strata. Also, it cannot be regarded as the bed rock to study the influence of it on the surface subsidence. The “hard soil-soft rock” transitional font has the support effect on the overlying strata during coal seam mining, which can restrict the surface subsidence. Furthermore, the larger the thickness of the transitional font is, the more obvious the restricting effect of it on the surface subsidence is. Meantime, this restricting effect will not be changed with the variation of the proportion between the loss bed and the bed rock thickness. Only the restricting extent is a little different.

With the continuous increase of the upper limit of coal mining, in mining areas near unconsolidated layers, water and sand inrush disasters occur from time to time, seriously threatening the safety of mine production. In this paper, the process of water and sand inrush accidents induced by mining near unconsolidated layers is analyzed using mechanical analysis and numerical simulation methods, based on the principle of silo unloading and arching and combined with actual water and sand inrush characteristics; the critical water and sand inrush arching mechanism is explained. The paper also proposed and established three critical arching mechanics models (interlocking arch, bonded arch, and transition arch), deduced the mathematical expression of interlocking arch and transition arch, and obtained the critical instability conditions of the arch and its influencing factors. The research results have guiding significance for the occurrence of water and sand inrush disasters and the judgment of the degree of damage in mining near unconsolidated layers.

High energy density materials are of interest, but density is the limiting factor for many organic compounds. Here the authors show the formation of a high density energetic compound from a two-step reaction between commercially available compounds that exhibit good heat thermal stability and detonation properties.

Damage to mine shafts located below thick loose aquifers, caused by coal seam mining, can seriously affect the operational safety of mines. In view of such a problem, the comprehensive weight method and the fuzzy matter-element analysis method were used to analyze and evaluate the stability of mine shafts below thick, loose aquifers. Based on data relating to shaft structure parameters collected from fifteen damaged shafts in coal mines in East China, a comprehensive analysis was performed. The results showed that (1) the two indexes of surface subsidence velocity and water level drop value at the bottom of a loose aquifer have a large influence on the stability of shafts below thick loose aquifers, and (2) the predicted results of thirteen sets of samples were the same as the results measured during actual production; the accuracy of the model was 86.67%. The comprehensive weight method and the fuzzy matter-element analysis model both show good reliability for evaluating the stability of mine shafts below thick loose aquifers and can provide a scientific reference for the analysis of the stability of mine shafts in areas with thick loose strata, as well as for the design of comprehensive control plans that could subsequently be implemented.

Recently, a sparse representation model - called an analysis sparse model - where the signal is multiplied by an analysis dictionary and the outcome is assumed to be sparse, has received increasing attention since it has potential and extensive applications in the area of signal processing. The performance of the analysis model significantly depends on an appropriately chosen dictionary. Most existing analysis dictionary learning algorithms are based on the assumption that the original signals are known or can be estimated from their noisy versions. Generally, however, the original signals are unknown or need to be estimated by using greedy-like algorithms with heavy computation. To solve the problems, we introduce a subset pursuit algorithm for analysis dictionary learning, where the observed signals are directly employed to learn the analysis dictionary. Next, a weighted split Bregman iteration algorithm is proposed to estimate original signals by the learned analysis dictionary. The experimental results demonstrate the competitive performance of the proposed algorithms compared with the state-of-art algorithms.

The effects of different laser shock peening (LSP) impacts on the three-dimensional displayed distributions of surface and in-depth residual stress at a laser spot of AISI 304 stainless steel were investigated by X-ray diffraction technology with the sin2φ method and MATLAB 2010a software. Microstructural evolution in the top surface subjected to multiple LSP impacts was presented by means of cross-sectional optical microscopy (OM) and transmission electron microscopy (TEM) observations. Experimental results and analysis indicated that residual stress distribution and microstructure at a laser spot depended strongly on the number of multiple LSP impacts, and refined grain and ultra-high strain rate play an important role in the improvement of compressive residual stress of AISI 304 stainless steel. The analysis of treatment of the extended surface was presented to obtain uniform surface properties on the top surface of AISI 304 stainless steel.

It is a new practical method to apply external magnetic field in magnetic working fluid to enhance heat transfer. In this paper, the swirl flow and heat transfer characteristics of ferrofluid in elliptical tubes under thermal-magnetic-flow fields coupling have been studied by using the finite volume method. The flow structure and secondary vortices evolution process of magnetic nanofluid in elliptical ducts under the action of the magnetic fields have been obtained. The effects of magnetic induction intensity and the ratio of major axis to minor axis of elliptical pipe on the flow and heat transfer performances have been main investigated. The results show that there is obvious secondary flow (with four vortices or eight vortices) on the cross-section and the swirling flow is gradually formed due to the coupling of thermal-magnetic-velocity fields. With the increase of the ratio of major axis to minor axis, the heat transfer enhancement effect with the application of external magnetic field is weakened. The comprehensive performance of flow and heat transfer are better at lower Reynolds number and higher magnetic induction intensity. [ABSTRACT FROM AUTHOR]