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Abstract The macro and micro morphology of rock failure surfaces play crucial roles in determining the rock mechanical and seepage properties. The morphology of unloaded deep rock failure surfaces exhibits significant variability and complexity. Surface roughness is closely linked to both shear strength and crack seepage behavior. Understanding these morphology parameters is vital for comprehending the mechanical behavior and seepage characteristics of rock masses. In this study, three-dimensional optical scanning technology was employed to analyze the micromorphological properties of limestone and sandstone failure surfaces under varying stress conditions. Line and surface roughness characteristics of different rock failure surfaces were then determined. Our findings reveal a critical confining pressure value (12 MPa) that influences the damage features of Ordovician limestone failure surfaces. With increasing confining pressure, pore depth and crack formation connecting the pores also increase. Beyond the critical confining pressure, the mesoscopic roughness of the failure surface decreases, and the range of interval-distributed pore roughness diminishes. Additionally, we conducted a detailed investigation into the water conductivity properties of rocks under different stress states using Barton's joint roughness coefficient (JRC) index and rock fractal theory. The roughness features of rock failure surfaces were classified into three categories based on mesoscopic pore and crack undulation forms: straight, wavy, and jagged. We also observed significant confining pressure effects on limestone and sandstone, which exceeding the critical confining pressure led to increased water conductivity in both rocks, albeit through different mechanisms. While sandstone exhibits fissures running across it, limestone shows shear abrasion holes. Beyond the critical confining pressure, the rock failure surface becomes smoother, leading to decreased water flow blocking capacity. The fractal dimension of Ordovician limestone increases significantly under critical confining pressure, leading to a more complex mesoscopic crack extension route.

To study the flow and strength characteristics of coal slime based backfill materials, orthogonal tests were used to design one cemented backfill material combining coal slime, high-water-content materials, cement, and fly ash. By using range, analysis of variance, and multi-variate regression analysis, influences of four key factors on the initial setting time, bleeding ratio, diffusivity, compressive strength, and shear strength of the backfill material were studied. These four factors include coal slurry water mass per cent concentration (A), high water material mass / slurry water mass (B), cement mass / slurry water mass (C) and fly ash mass / slurry water mass (D). Results show that initial setting time, diffusivity, compressive strength, and shear strength of the backfill material are 52−67 min, 42.0−76.5 cm, 0.076−0.247 MPa, and 0.033−0.139 MPa, respectively, all distributed in wide ranges. For initial setting time, the four factors are listed in a descending order as B>C>A>D according to their influences; for the compressive strength, the four factors are ranked as D>C>A>B; for the shear strength, the four factors are listed in an order as C>D>A>B. Mathematical equations between A, B, C, D and initial setting time, diffusivity, compressive strength, and shear strength were gotten, initial setting time and A, B presents quadratic function relation, and C, D present exponential relation; diffusivity and A, B, C presents quadratic function relation, and D presents trigonometric relation; compressive strength and A, D presents exponential relation, and B, C presents quadratic function relation; shear strength and A, B presents quadratic function relation, and C, D presents exponential relation.One prediction model for characteristic parameters, namely, fluidity and strength, of the coal slime based backfill material under action of various factors was established and calibrated.

Peripheral nerve injuries may result in severe long-gap interruptions that are challenging to repair. Autografting is the gold standard surgical approach for repairing long-gap nerve injuries but can result in prominent donor-site complications. Instead, imitating the native neural microarchitecture using synthetic conduits is expected to offer an alternative strategy for improving nerve regeneration. Here, we designed nerve conduits composed of high-resolution anisotropic microfiber grid-cordes with randomly organized nanofiber sheaths to interrogate the positive effects of these biomimetic structures on peripheral nerve regeneration. Anisotropic microfiber-grids demonstrated the capacity to directionally guide Schwann cells and neurites. Nanofiber sheaths conveyed adequate elasticity and permeability, whilst exhibiting a barrier function against the infiltration of fibroblasts. We then used the composite nerve conduits bridge 30-mm long sciatic nerve defects in canine models. At 12 months post-implant, the morphometric and histological recovery, gait recovery, electrophysiological function, and degree of muscle atrophy were assessed. The newly regenerated nerve tissue that formed within the composite nerve conduits showed restored neurological functions that were superior compared to sheaths-only scaffolds and Neurolac nerve conduit controls. Our findings demonstrate the feasibility of using synthetic biophysical cues to effectively bridge long-gap peripheral nerve injuries and indicates the promising clinical application prospects of biomimetic composite nerve conduits.

North China coalfield is one of the most severe coal fields threatened by Ordovician limestone water (buried depth exceeding 1000 m). In this paper, the hydraulic mechanism of Ordovician limestone water in the complex geological structure are studied. An interesting phenomenon was found in the study, the water inrush from Ordovician limestone has a “latent period” and presents lag water inrush law. The hydrochemical characteristics of the early stage in Xingdong coal mine is non-Ordovician limestone water chemical characteristics, the later stage gradually shows the Ordovician limestone water with the continuous outflow. Meanwhile, the hyperbolic contour distribution characteristics are also observed in the spatial distribution law of microseismic in the floor working face. The minimum damage area is in the layer at the hyperbolic apex, which is the critical breakthrough point of water inrush. Furthermore, the water inrush fracture mechanics model (WIFM) of concealed fault with high confined water is established based on the fracture mechanics theory. The results show that the critical values of the length and angle of the water inrush of the conceal fault are about 50 m and 40°. It should be pointed out that the longer and larger angle conceal faults indicate the longer of the fracture expansion at the tip of the fault, and the probability of water inrush increases. Special attention should be paid to such concealed faults and methods such as grouting should be adopted to avoid the water inrush disaster caused by the activation of faults. This model provides a theoretical basis for the mechanical mechanism of the coal seam floor water inrush process.

Abstract Background Y-STR polymorphisms are useful in tracing genealogy and understanding human origins and migration history. This study aimed to fill a knowledge gap in the genetic diversity, structure, and haplogroup distribution of the Han and Manchu populations from the three northeastern provinces in China (Liaoning, Jilin, and Heilongjiang). Methods A total of 1,048 blood samples were collected from unrelated males residing in Dalian. Genotyping was performed using the AGCU Y37 + 5 Amplification Kit, and the genotype data were analyzed to determine allele and haplotype frequencies, genetic and haplotype diversity, discrimination capacity, and haplotype match probability. Population pairwise genetic distances (F st ) were calculated to compare the genetic relationships among Han and Manchu populations from Northeast China and other 23 populations using 27 Yfiler Plus loci set. Multi-dimensional scaling and phylogenetic analysis were employed to visualize the genetic relationships among the 27 populations. Moreover, haplogroups were predicted based on 27 Yfiler Plus loci set. Results The Han populations from Northeast China exhibited genetic affinities with both Han populations from the Central Plain and the Sichuan Qiang population, despite considerable geographical distances. Conversely, the Manchu population displayed a relatively large genetic distance from other populations. The haplogroup analysis revealed the prevalence of haplogroups E1b1b, O1b, O2, and Q in the studied populations, with variations observed among different ethnic groups. Conclusion The study contributes to our understanding of genetic diversity and history of the Han and Manchu populations in Northeast China, the genetic relationships between populations, and the intricate processes of migration, intermarriage, and cultural integration that have shaped the region’s genetic landscape.

The damage and failure process of rock engineering is inseparable from rock dilatancy. Dilatancy is the phenomenon of rock volume increase after the differential stress exceeds the yield limit. X-ray diffraction, scanning electron microscope, and uniaxial compression tests under different stress loading rates (0.1, 0.5, 2.0, 5.0 kN/s) were carried out on mudstone specimens from drill holes in the mine site with a depth of nearly 1300 m. The results demonstrate that the mudstone is mainly composed of plagioclase. The distribution of various minerals in the rock is not uniform. The main component plagioclase is distributed in strips, filled with other minerals, the filling material is mainly chlorite. Under different stress loading rates, the axial strain curves are typical plastic-elastic-plastic curves, and each specimen has an obvious micro-crack compaction process. The lower the stress loading rate, the more pronounced the compaction process, that is, the smoother the curve. In the elastic stage, the slope of the curve increases as the stress loading rate increases, indicating that the rock’s elastic modulus rises. The one-way analysis of variance method was used to test the significance of the differences in each analysis item’s data. The results indicate that the stress loading rate (Vload) is related to the uniaxial compressive strength (σc), elastic modulus(E), maximum axial strain(εa,max), maximum radial strain(εd,max), the initial dilatancy strength(f*), and the ratio of the initial dilatancy stress to the uniaxial compressive strength(f*/σc) of mudstone. It does not correlate with the maximum volumetric strain value (εV,max), and the ratio of the initial dilatancy volumetric strain to the maximum volumetric strain (εV,d/εV,max). As the Vload increases, σc and E increase, when Vload increases 50 times from 0.1 kN/s to 5.0 kN/s, the measured σc increases from 26.8 MPa to 36.5 MPa, and E increases from 3.5 GPa to 5.9 GPa. The εa,max and εd,max decrease with increasing Vload while axial and radial strain rates increase. Hence, the likelihood of failure of mudstone rock under insufficient deformation increases with increasing Vload. The f* and f*/σc decrease as Vload increases, meaning that it is easier to enter the dilatancy stage with higher Vload. It is considered that the strength parameters, deformation and dilatancy parameters of mudstone are significantly dependent on Vload.

Phosphogypsum (PG), a byproduct during the phosphoric acid production process, also known as the wet process, contains complex and diverse impurities, resulting in low utilization and considerable accumulation. This leads to a massive waste of land resources and a series of environmental pollution problems. Given the current urgent ecological and environmental situation, developing impurity removal processes with low energy consumption and high efficiency, exploring valuable resource recovery, preparing high value-added PG products, and broadening the comprehensive utilization ways of PG are significant strategies to promote the sustainable consumption of PG and sustainable development of the phosphorus chemical industry. This review comprehensively summarizes the advantages and disadvantages of existing PG impurity removal and utilization technologies and probes into the future development direction, which provides references and ideas for subsequent PG research.

A fault disrupts the continuity of the rock strata in a mining area. To study the law governing the fracture of overlying strata in mining areas under discontinuous boundary conditions, the overlying strata were redefined and grouped based on the activity characteristics of each rock layer during the overall movement of the overlying strata. The activity patterns of different layers of the fault were obtained through the movement and failure forms of each group of rock layers. The relationship among the size of the coal pillar at the boundary of the fault, the dip angle of the fault, and the movement angle of the rock strata was considered. A model of the spatial relationship between the overlying rock movement zone of the quarry and the fault surface was established. The limit equilibrium equations of the key layer in the fault zone before breaking were established based on the tensile strength of the rock layer. In addition, the mechanical slip instability criterion and the deflection instability criterion of the discontinuous-boundary rock mass are given herein. Based on a field case, a double criterion was used to determine the initiating activated rock layers of the fault in the cases where the fault dip was smaller than the rock movement angle. Rock movement during excavation was simulated by similar simulation tests, and different levels of rock movement patterns in the boundary fault zone were focused on monitoring and analyzing. The stress and displacement changes in different rock layers in the fault zone were analyzed with numerical simulation results. The results show the following: if the dip angle of the fault is smaller than the movement angle of the rock layer, the delamination space of the fault surface is mainly distributed in the bending and sinking zone of the overlying rock; with an increase in the working-face advancement distance, the vertical pressure of the upper part of the fault gradually decreases, and the stress-concentration area in the middle and lower part of the fault gradually increases; the rock layer of the upper part of the fault, which is mainly composed of the key stratum, is the main area of activation of the fault.

Abstract Free chlorine is one of the key water quality parameters in tap water. However, a free chlorine sensor with the characteristics of batch processing, durability, antibiofouling/antiorganic passivation and in situ monitoring of free chlorine in tap water continues to be a challenging issue. In this paper, a novel silicon-based electrochemical sensor for free chlorine that can self-clean and be mass produced via microfabrication technique/MEMS (Micro-Electro-Mechanical System) is proposed. A liquid-conjugated Ag/AgCl reference electrode is fabricated, and electrochemically stable BDD/Pt is employed as the working/counter electrode to verify the effectiveness of the as-fabricated sensor for free chlorine detection. The sensor demonstrates an acceptable limit of detection (0.056 mg/L) and desirable linearity (R 2 = 0.998). Particularly, at a potential of +2.5 V, hydroxyl radicals are generated on the BBD electrode by electrolyzing water, which then remove the organic matter attached to the surface of the sensor though an electrochemical digestion process. The performance of the fouled sensor recovers from 50.2 to 94.1% compared with the initial state after self-cleaning for 30 min. In addition, by employing the MEMS technique, favorable response consistency and high reproducibility (RSD

Taking the geological conditions of a coal mine in Liupanshui City, Guizhou Province, as the background. The fracture law of the roof in the coal face and the height of the “Two zones” were obtained through theoretical analysis and empirical formula calculation, and the results were verified using similar simulation experiments. Through numerical simulation were researched the stress distribution characteristics of the overlying strata on the working face under the influence of multiple faults. The results showed that in the early stage of mining, F1 undergoes activation under the influence of the main roof weighting, leading to an increase in the degree of plastic damage to the coal seam and strata behind the working face, causing a redistribution of the behind abutment pressure. Finally, under the influence of the F1 barrier effect, the vast majority of the behind abutment pressure is transferred to the lower strata of F1, leading to a continuous increase in stress concentration there. But as the working face continues to advance, the blocking effect of the roof plastic zone above the goaf on the transmission of the behind abutment pressure of the working face begins to appear and continues to increase, leading to a decrease in the peak stress at the lower strata of F1. The stress change process on the F2 side is similar to that on the F1 side, the front abutment pressure is initially distributed in the strata in front of the working face, but as the activation degree of F2 continues to intensify, it gradually shifts to the lower strata of F2, and ultimately the majority of the front abutment pressure is borne by the lower strata of F2.

In this paper, the properties of superfine cement with different mesh sizes are observed from both macro and micro perspectives through laboratory tests, and the fluidity, stability, and mechanical properties of superfine cement are studied in depth. The results show that increasing the mesh size of superfine cement can reduce the influence of the water-cement ratio on slurry, reduce the fluidity of superfine cement, and enhance its stability. The strength of the superfine cement stone specimen will increase with the increase in cement mesh number, and the higher the mesh number, the shorter the time required for the superfine cement stone specimen to reach its maximum strength. Considering the performance, cost, and storage difficulty, the superfine cement with the mesh size of K700 is more cost-effective. Using K700 superfine cement grout can effectively reduce the impact of geostress on the surrounding rock of the roadway and inhibit the deformation and damage of the surrounding rock.

The increasing demand for rare earth elements (REEs), especially from new and innovative technology, has strained their supply, which makes the exploration of new REE sources necessary, for example, the recovery of REEs from phsophogypsum (PG). PG is a byproduct during the wet production of phosphoric acid, which is an attractive secondary resource for REEs due to a large amount of REEs locked in them. In most cases, REEs contained in PG are mainly encapsulated in the gypsum crystal, leading to a low leaching efficiency. Therefore, it is particularly important to use various methods to enhance the leaching of REEs from PG. In this review, we summarized and classified various enhanced leaching methods for the recovery of REEs from PG, and the advantages and disadvantages of different methods were compared. A joint method of recrystallization and RIL may be a promising enhanced leaching approach for the recovery of REEs from PG. Recrystallization could achieve both the complete REE release and simultaneous preparation of industrial materials with high value added, such as high-strength α-hemihydrate gypsum by phase transformation of PG, and the RIL technology could adsorb the releasing REEs and realize their efficient extraction. Such a combination appears to show significant advantages because of high REE recovery, as well as high value-added product preparation at low cost.

For coal mines, rock, coal, and rock bolt are the critical constituent materials for surrounding rock in the underground engineering. The stability of the “rock-coal-bolt” (RCB) composite system is affected by the structure and fracture of the coal-rock mass. More rock bolts installed on the rock, more complex condition of the engineering stress environment will be (tensile-shear composite stress is principal). In this paper, experimental analysis and theoretical verification were performed on the RCB composite system with different angles. The results revealed that the failure of the rock-coal (RC) composite specimen was caused by tensile and shear cracks. After anchoring, the reinforcement body formed inside the composite system limits the area where the crack could occur in the specimen. Specifically, shearing damage occurred only around the bolt, and the stress-strain curve presented a better post-peak mechanical property. The mechanical mechanism of the bolt under the combined action of tension and shear stress was analyzed. Additionally, a rock-coal-bolt tensile-shear mechanical (RCBTSM) model was established. The relationship (similar to the exponential function) between the bolt tensile-shear stress and the angle was obtained. Moreover, the influences of the dilatancy angle and bolt diameter of the RCB composite system were also considered and analyzed. Most of the bolts are subjected to the tensile-shearing action in the post-peak stage. The implications of these results for engineering practice indicated that the bolts of the RCB composite system should be prevented from entering the limit shearing state early.

In this paper, we propose an improved energy optimization clustering algorithm (EOCA) for the multi-hop underwater acoustic cooperative sensor networks (UWA-CSN) due to the limited energy supply of the underwater sensor nodes. The proposed EOCA scheme considers multiple factors, such as the number of neighbor nodes, the residual energy of each node, the motion of the sensor nodes caused by the ocean currents, and the distance between the sink node and each underwater sensor node. All these factors are considered within the framework of the multi-hop cooperative communication. Moreover, in the proposed energy optimization scheme, we define a residual energy based maximum effective communication range (reE-MECR) according to the residual energy of each underwater sensor node, which can adaptively control the energy consumption of data transmission for each hop. Compared with the existing clustering scheme, the experimental results demonstrate that the proposed EOCA scheme can not only prolong the life time of the multi-hop UWA-CSN, but also keep a good communication and networking performance, including the package delivery ratio, the energy consumption efficiency, and the network coverage area. The proposed scheme can obtain both the clustering benefit and the cooperative communication benefit for the multi-hop UWA-SN in terms of energy saving in underwater environments.

ObjectivesTo assess the efficacy of Y-chromosome mini-STR-based next-generation sequencing (NGS) for non-invasive prenatal paternity testing (NIPPT).MethodsDNA was extracted from the plasma of 24 pregnant women, and cell-free fetal DNA (cffDNA) haplotyping was performed at 12 Y-chromosome mini-STR loci using the Illumina NextSeq 500 system. The cffDNA haplotype was validated by the paternal haplotype. Subsequentlly, the paternity testing parameters were attributed to each case quantitatively.ResultsThe biological relationship between the alleged fathers and infants in all 24 family cases were confirmed by capillary electrophoresis (CE). The Y-chromosome mini-STR haplotypes of all 14 male cffDNA were obtained by NGS without any missing loci. The alleles of cffDNA and paternal genomic DNA were matched in 13 cases, and a mismatched allele was detected at the DYS393 locus in one case and considered as mutation. No allele was detected in the 10 female cffDNA. The combined paternity index (CPI) and probability of paternity calculation was based on 6 loci Y-haplotype distributions of a local population. The probability of paternity was 98.2699-99.8828% for the cases without mutation, and 14.8719% for the case harboring mutation.ConclusionsOur proof-of-concept study demonstrated that Y-chromosome mini-STR can be used for NGS-based NIPPT with high accuracy in real cases, and is a promising tool for familial searching, paternity exclusion and sex selection in forensic and medical applications.

Under the influence of tectonism in geological activities, most fault structures appear in groups. Multiple fault structures can induce a variety of mine dynamic disasters, which significantly affect the safety of mine production. To study the dynamic instability mechanism of the strata in the multifault structure zone of the stope when mining, a numerical model of multiple fracture structures was established. At the same time, the mechanism of the dynamic instability of the rock formation in the multifault structure zone of the stope has been studied through similar simulation experiments and on-site data analysis. The research results show that the stress-affected areas of the faults in the multiple-fault structure area overlap, and the stress evolution law of the fault will distinguish its independent dynamic evolution model. The multifault structure area has a multifault overall evolution law model. In this model, there is a synergy between the fault layers, and the maximum value of stress concentration is diagonally distributed. Under the influence of mining, the fault structure will be activated to change the stress field distribution form of the stope. The two faults in multiple structural areas have a joint mechanism, which plays a key role in controlling the dynamic instability process of the surrounding rock of the stope. The first activated faults in the multiple-fault structure area will undergo secondary activation under the influence of subsequent fault activities. The evolution law of cracks in the overburden of similar simulation experiments confirms that the early active F1 fault will be affected by the subsequent F2 fault activity. The mine pressure data measured on-site verifies the reliability of the numerical simulation experiment and the similar simulation experiment.

Microseismic source location is the core of microseismic monitoring technology in coal mining; it is also the advantage of microseismic monitoring technology compared with other monitoring methods. The source location method directly determines the accuracy and stability of the source location results. Based on the problem of non-benign arrays of microseismic monitoring sensors in the coal mining process, a fast location method of microseismic source in coal mining based on the NM-PSO algorithm is proposed. The core idea of the NM-PSO algorithm is to use the particle swarm optimization (PSO) algorithm for global optimization, reduce the size of the solution space and provide the optimized initial value for the Nelder Mead simplex algorithm (NM), and then use the fast iteration characteristics of the NM algorithm to accelerate the convergence of the model. The NM-PSO algorithm is analyzed by an example and verified by the microseismic source location engineering. The NM-PSO algorithm has a significant improvement in the source location accuracy. The average location errors in all directions are (5.65 m, 5.01 m, and 7.21 m), all Within the acceptable range, and they showed good universality and stability. The proposed NM-PSO algorithm can provide a general fast seismic source localization method for different sensor array deployment methods, which significantly improves the stability and result in the accuracy of the seismic source localization algorithm and has good application value; this method can provide new ideas for research in microseismic localization in coal mining.

The binder‐free freestanding electrode is assumed as a proven and effective method of increasing the energy density of potassium‐ion batteries (PIBs) because of the addition of binder and conductor. However, an expensive and complex synthesis process hampers its development, Herein, a binder‐free freestanding biomass hard carbon (BHC) foam with balsa wood as the precursor is put forward. The prepared BHC foam maintains a highly hierarchical structure, in which the channels are interconnected and the pipe walls form an extremely stable 3D structure. This 3D porous network is synthesized in one step by a simple, environmentally friendly method, which ensures efficient ion and electrolyte transfer without structure collapse during the electrochemical cycle. When used as PIB anodes, the binder‐free freestanding carbon foam delivers a high reversible capacity of 252.7 mAh g−1 at 100 mA g−1 with a high initial coulombic efficiency of 63.7%, excellent long cycle stability (95.1% capacity retention after 500 cycles, and the average decay rate per cycle is 0.012% over 2500 cycles), and superior rate capability (the capacity of 165 mAh g−1 reserved at 2000 mA g−1). This strategy provides a simple and fast way to fabricate a stable and high‐performance anode for PIBs.

To investigate the strength characteristics of mudstone in deep-buried coal-measure formation, four types of experiments have been conducted: (i) the X-ray diffraction (XRD) test; (ii) the scanning electron microscope (SEM) scanning test; (iii) the point load strength index test; and (iv) the uniaxial compressive strength test. It was concluded that the mudstone of the deep-buried coal measures in the Longtan Formation is dominated by chlorite, quartz, and albite using the XRD test, of which chlorite is primary, accounting for 74.3%. It was found that the three minerals in the mudstone are unevenly distributed using the SEM scanning test, albite is irregularly distributed in chlorite, and quartz is present in the albite and chlorite. Sixty-five specimens were tested for the point load strength index. After processing the data using the method suggested by the International Society for Rock Mechanics and Rock Engineering(ISRM), it was found that the maximum value of Is(50) was 6.10 MPa, the minimum is 0.14 MPa, and 53% of the specimens’ Is(50) values are below 2.0 MPa. The RMT-150C rock mechanics testing machine was used to conduct uniaxial compression tests on six specimens. The maximum uniaxial compressive strength (UCS) value is 59.26 MPa, the minimum value is 31.77 MPa, and the average is 45.64 MPa. Linear fitting and logarithmic fitting are carried out for the correlation between UCS and Is(50). The goodness of fit R2 of the linear fitting is 0.863, and that of the logarithmic fitting is 0.919, indicating a strong correlation between them. When it is challenging to make standard specimens, Is (50) can be used to estimate UCS.

Gob-side entry retained with roadside filling (GER-RF) plays a key role in achieving coal mining without pillar and improving the coal resource recovery rate. Since there are few reports on the cyclic filling length of GER-RF, a method based on the stress difference method is proposed to determine the cyclic filling length of GER-RF. Firstly, a stability analysis mechanics model of the immediate roof above the roadside filling area was established, and then, the relationship between the roof stress distribution and the unsupported roof length was obtained by the stress difference method. According to the roof stability above the roadside filling area based on the relationship between the roof stress and its tensile strength, the maximum unsupported roof length and rational cyclic filling length were determined. Combined with the geological conditions of the 1103 thin coal seam working face of Heilong Coal Mine and the 1301 thick coal seam working face of Licun Coal Mine, the suggested method was applied to determine that the rational cyclic filling lengths were 2.4 m and 3.2 m, respectively. Field trial tests show that the suggested method can effectively control the surrounding rock deformation along with rational road-in support and roadside support and improve the filling and construction speed.

It is a complex issue to select the support structure parameters for a deep-buried roadway with fractured surrounding rock; especially when the support structure parameters need to be adjusted, the influence degree of support structure parameters on roadway deformation needs to be determined. The deformation of deep-buried roadway’s fractured surrounding rock development was investigated using multi-index orthoplan in this paper. According to the coal mine field investigation, support structure’s failure often occurs, and some need to be repaired many times. Through the roadway surrounding rock drilling, it was found that the stress of the surrounding rock was relieved, resulting in the cavity and separation of the stratum layer. The two sidewalls’ development and roof fractures are mainly tangential, and the original rock state appears only beyond 6.3∼8.2 m. The length of bolts, the row distance between bolts, the length of cables, and the row distance of U-shaped steel were selected as control factors in the multi-index orthogonal design, and roadway’s deformation values were taken as the test indexes. According to the orthoplan, nine numerical simulation schemes were designed, and FLAC3D was used for establishment. The range analysis method was used to analyze the test results. The results show that the control factors’ influence order on the total deformation of the roadway is as follows: row spacing between U-shaped steel > bolt length > cable length > row spacing between bolts, the influence order on the deformation of the roadway floor is as follows: row spacing between U-shaped steel > row spacing between bolts > bolt length > cable length, same as the left sidewall and right sidewall, and the influence order on the roadway roof’s deformation is as follows: row spacing between U-shaped steel > bolt length = cable length > row spacing between bolts, which provide a reference for the support design of deep-buried roadways with fractured surrounding rock, especially the adjustment of the supporting structure.

The characterization and leaching mechanism of REEs from phosphogypsum (PG) in HCl was studied in-depth. REEs contained in the PG were 208 ppm, of which Y, La, Ce, and Nd were the four most abundant elements. The modes of occurrence of rare earth elements (REEs) in the PG were quantified using the sequential chemical extraction (SCE) method. Among the five REE occurrence species, the metal oxide form accounted for the largest proportion, followed by the residual, organic matter, and ion-exchangeable fractions, and REEs bound to carbonates were the least. From the comparison of the distributions of REEs and calcium in different occurrence states, it can be determined that REEs contained in the PG were mainly present in the residue state (existed in the gypsum lattice) and the metal oxide state (easily leached). The leaching results show that the suitable leaching conditions were acid concentration of 1.65 mol/L, S/L ratio of 1/10, and reaction temperature of 60 °C. At the condition, the maximum leaching efficiency for ∑REE was 65.6%, of which the yttrium leaching rate was the highest and reached 73.8%. Importantly, A new kinetic equation based on the cylindrical shrinking core model (SCM) was deduced and could well describe REE leaching process from PG. The apparent activation energy for ∑REE leaching was determined to be 20.65 kJ·mol−1.

In this study, both theoretical analysis and similar simulation experiment are employed to investigate the overburden failure law of fully mechanized face in the steep coal seam. By establishing the mechanical model of inclined rock beam, the deflection equation of overlying strata beam is obtained. Based on the geological conditions of Xiangyong coal mine in Hunan Province of China, the laws of roof deformation and failure in steep coal seam are obtained by similar simulation experiments. The results showed that the roof deformation of the goaf is relatively large after the working face advances along the strike, and the deformation mainly occurs in the upper roof of the goaf. The backward gangue in the immediate roof fills the lower part of the goaf, which plays a supporting role in the lower part of the roof and floor. The roof fracture of goaf is located in the middle and upper parts of the working face, which is consistent with the results derived from the mechanical model. After the roof fracture, a “trapezoid” bending fracture area and the secondary stability system area is formed, which is composed of four areas: the lower falling and filling support area, the upper strata bending fracture area, the fracture extension area, and the roof bending sinking area.

The selection of the support scheme for deep-buried and large-span chambers has been a severe problem in underground engineering. To further study the mechanical mechanism of large deformation, based on the repair engineering of the chambers of Pingdingshan No.6 mine in China, the field investigation, laboratory test, numerical simulation, and theoretical analysis were studied. The surrounding rock of the central substation chamber (CSC) and the main pumping chamber (MPC) were classified according to the rock mass rating (RMR) classification method, and the main factors affecting the stability of the surrounding rock of the chambers were revealed. A prediction model of mechanical parameters of the surrounding rock was established based on the Hoek-Brown failure criterion. Additionally, the prediction results were used in FLAC3D to further analyze the failure of the original support scheme, and the feasibility of the restoration plan was proposed. Six key points of support technology for this kind of chamber were put forward. Comprehensive support and repair scheme, including “bolt, metal mesh, shotcrete, grouting, anchor cable, and combined anchor cable,” was put forward. The engineering practice indicated that the deformation rate was less than 0.7 mm/d, which was beneficial to the long-term stability of CSC and MPC. The implementation of this restoration project can provide a reference for other similar projects.

In this paper, the research background is the filling and mining of the landscape mineral paste body in Baixian State, Guangxi, China. The strength test of the new paste filling material is carried out by the materials of coal zircon, red soil, and cement, the best ratio between the materials is obtained, and the hydration mechanism of the new paste filling material is studied by XRD diffraction instrument and SEM (scanning electron microscopy) test. The types of hydration products and microstructure forms of filling materials in different age periods are revealed. The test results show that the optimal ratio of the new paste filling material in the coal mine is the quality ratio of coal zircon: red soil: cement as 6 : 2 : 1, and the slurry concentration is 80%, which can not only meet the transportation requirements required by the filling process but also reduce the cost of filling, and with the extension of the maintenance age, the filling material produces more gel products, and the overall structure is more encrypted.

In order to study the influence of burial depth on the roadway deformation, the deformation data of more than 100 roadways were collected and classified. The results have shown that, in the first 5 days of new digging roadways, the surrounding rock deformation is basically not affected by the buried depth. The influence period of roadway deformation with different depths is the same, namely, the severe period (1∼15 days), the mitigation period (15∼35 days), and the stable period (35∼50 days). With the increase in depth, the surrounding rock deformation increment of new digging roadways with a depth of 300∼600 m is much larger than that of 600∼900 m. Within 100 m of the working face from the monitoring point, the deformation of mining roadways can be divided into two stages: severe impact (10∼60 m) and stable impact (60∼100 m). With the increase in depth, the deformation increment of the surrounding rock in the mining roadways with a depth of 600∼900 m is much larger than that of 300∼600 m. The surrounding rock deformation increases with the increase in the width and height of roadways and gradually increases with the decrease in the strength of rock mass.

Background/Aims: MiR-19b has been reported to be involved in several malignancies, but its role in multiple myeloma (MM) is still unknown. The objective of this study was to explore the biological mechanism of miR-19b in the progression of MM. Methods: First, we performed real-time polymerase chain reaction (PCR) and Western blot to study the expression of miR-19b, tuberous sclerosis 1 (TSC1), and caspase-3 in different groups. MTT assay was performed to explore the effect of miR-19b on survival and apoptosis of cancer stem cells (CSCs). Computation analysis and luciferase assay were utilized to confirm the interaction between miR-19b and TSC1. Results: A total of 38 participants comprising 20 subjects with MM and 18 healthy subjects as normal controls were enrolled in our study. Real-time PCR showed dramatic upregulation of miR-19b, but TSC1 was evidently suppressed in the MM group. MiR-19b overexpression substantially promoted clonogenicity and cell viability, and further inhibited apoptosis of CSCs in vitro. Furthermore, miR-19b overexpression downregulated the expression of caspase-3, which induced apoptosis. Using in silico analysis, we identified that TSC1 might be a direct downstream target of miR-19b, and this was further confirmed by luciferase assay showing that miR-19b apparently reduced the luciferase activity of wild-type TSC1 3´-UTR, but not that of mutant TSC1 3´-UTR. There was also evident decrease in TSC1 mRNA and protein in CSCs following introduction of miR-19b. Interestingly, reintroduction of TSC1 abolished the miR-19b-induced proliferation promotion and apoptosis inhibition in CSCs. Conclusion: These findings collectively suggest that miR-19b promotes cell survival and suppresses apoptosis of MM CSCs via targeting TSC1 directly, indicating that miR-19b may serve as a potential and novel therapeutic target of MM based on miRNA expression.

High-quality training samples are essential for accurate land cover classification. Due to the difficulties in collecting a large number of training samples, it is of great significance to collect a high-quality sample dataset with a limited sample size but effective sample distribution. In this paper, we proposed an object-oriented sampling approach by segmenting image blocks expanded from systematically distributed seeds (object-oriented sampling approach) and carried out a rigorous comparison of seven sampling strategies, including random sampling, systematic sampling, stratified sampling (stratified sampling with the strata of land cover classes based on classification product, Latin hypercube sampling, and spatial Latin hypercube sampling), object-oriented sampling, and manual sampling, to explore the impact of training sample distribution on the accuracy of land cover classification when the samples are limited. Five study areas from different climate zones were selected along the China–Mongolia border. Our research identified the proposed object-oriented sampling approach as the first-choice sampling strategy in collecting training samples. This approach improved the diversity and completeness of the training sample set. Stratified sampling with strata defined by the combination of different attributes and stratified sampling with the strata of land cover classes had their limitations, and they performed well in specific situations when we have enough prior knowledge or high-accuracy product. Manual sampling was greatly influenced by the experience of interpreters. All these sampling strategies mentioned above outperformed random sampling and systematic sampling in this study. The results indicate that the sampling strategies of training datasets do have great impacts on the land cover classification accuracies when the sample size is limited. This paper will provide guidance for efficient training sample collection to increase classification accuracies.

After a gas drainage event causes different degrees of initial porosity in the coal seam, the heterogeneity of the coal mass becomes much more obvious. In this paper, soft coal testing samples with different degrees of heterogeneity were prepared first by a new special experimental research method using hydrogen peroxide in an alkaline medium to generate oxygen. Then, a series of mechanical tests on the soft coal mass samples were carried out under multiple factor coupling conditions of different heterogeneities and confining pressures. The results show that with a low strength, the ductility failure characteristic and a kind of rheology similar to that for soft rock flow were reflected for the soft coal; i.e., the stress-strain curve of the coal mass had no apparent peak strain and residual strength. An interesting phenomenon was found in the test process: there was an upwardly convex critical phase, called the brittle-ductile failure transition critical phase, for the heterogeneous soft coal mass between the initial elastic compression phase and the ductile failure transition phase in the stress-strain curve of the coal mass. An evolution of the brittle-ductile modulus coefficient of the soft coal was developed to analyze the effect of the internal factor (degree of heterogeneity) and external factors (confining pressure) on the transition state of the brittle-ductile failure of soft coal. Further analysis shows that the internal factor (heterogeneity) was also one of the essential factors causing the brittle-ductile transition of soft coal.

INTRODUCTION:Bladder cancer (BC) is one of the most common urologic malignancies and it is urgently needed to identify novel potential prognostic biomarkers for predicting prognosis and progression of patients with BC in clinical practice. Previous research has revealed that long noncoding RNAs (lncRNAs) played critical roles in BC, and may serve as novel potential prognostic biomarkers in patients with BC. Therefore, we conducted this meta-analysis to clarify the prognostic potential of lncRNAs in BC patients. METHODS:A comprehensive search was performed in PubMed, Web of Science, and China National Knowledge Infrastructure (CNKI). According to the predefined exclusion and inclusion criteria, a total of 9 recently published articles comprising 13 lncRNAs and 666 BC patients were included into this meta-analysis. We analyzed the hazard ratios (HRs) and 95% confidence intervals (CIs) to determine the relationship between lncRNAs expression and survival outcomes. We also analyzed the odds ratio (ORs) and 95% confidence intervals (CIs) to assess the association between lncRNAs expression and clinicopathological characteristics, including histological grade, gender, multifocality, tumor size, and tumor stage. RESULTS:Our results revealed that high lncRNAs expression was associated with shorter overall survival in Asian BC patients (pooled HR = 2.32, 95% CI: 1.35-4.00, P = 0.002, random-effect). High lncRNAs expression levels were significantly associated with histological grade (G2-G3 vs. G1: OR = 3.857, 95%CI: 1.293-11.502, P = 0.015, random-effect). CONCLUSIONS:In summary, this meta-analysis has demonstrated that lncRNAs could be used as potential prognostic markers for BC and high lncRNAs expression could predict poor prognosis among Asian BC patients.

The surrounding rock deformation in the underground mining roadway increases rapidly during excavation and mining disturbance. The semirock and coal roadway, which is formed by the rock and coal composite system, will show different mechanical properties. Therefore, loading rate and anchoring or not are critical to grasp the stability law of the rock-coal combination system under different conditions. The uniaxial mechanical test under the constant loading rate and combined loading rate is carried out in the static loading range (0.01∼10 mm·min−1) of the rock-loose coal composite specimen (RCCS). The test results show that the rock and loose coal composite specimen without bolt (RCB(0) specimen) are abnormal, and the uniaxial compressive strength (UCS) and residual strength (RS) of the specimen do not increase but decrease with the increase of loading rate. In contrast, the UCS of the rock-loose coal composite specimen with the bolt (RCB(1∼2) specimen) is consistent with that of the ordinary hard and brittle rock, which increases with the increase of loading rate. To a certain extent, the initial damage and the development of microcracks in loose coal bodies are limited by bolts. Finally, the deformation mechanism and constitutive equation of the rock-loose coal composite system are discussed.

The purpose of this paper is to solve the problem that deep and close-distance cavern and roadway group were easily affected by the adjacent chamber or roadway excavation disturbance and low stability and significant deformation of surrounding rock occurred. The stability and control technology of surrounding rock in the main shaft and auxiliary shaft system has been analyzed by the adjacent chamber and roadway group of −850 m level in Qujiang Mine, China, as an engineering background. Firstly, the numerical calculation of the excavation chamber was, respectively, carried out in different ways with the propagation theory of the excavation disturbance wave. The results show that the interaction of adjacent chamber excavation was more intense. When excavated at the same time, there is a large increase in the movement of the sides and the roof-floor of the chamber and roadway. Then, the mechanism of interaction between low-high stress and excavation disturbance was considered, the corresponding control principles were provided, and a set of critical technologies and equipment were designed according to the deformation characteristics of the large deformation soft surrounding rock. Finally, the comprehensive control method was put forward with the water pump house as an example, that is, anchor, metal net, grouting, combined anchor cable and large-diameter anchor cable. And the related support parameters were determined by the internal damage of the surrounding rock chamber. The numerical simulation results show that the surrounding rock deformation of the chamber and roadway reduced with the revised support program, which the expansion of the rock mass loose circle prevented effectively. The site test shows that the convergence rate of surrounding rock with the improved support was less than 0.2 mm/d, and the rock deformation of chamber and roadway suppressed significantly.

Field investigations of high stress soft rock deformations show that the high stress soft rock roadway can slide with large deformation. Severe extrusion and floor heave can also be subsequently observed. The supported roadway can be locally damaged or completely fail, where the floor has a large deformation and/or is seriously damaged. The factors inducing large deformation of surrounding rocks in deep roadway are rock strengths, structure face cutting types, stress states, stress release, support patterns, and construction methods. Based on the deformation characteristics of high stress soft rock roadway, a comprehensive support scheme is proposed. The overall support technology of “step-by-step and joint, hierarchical reinforcement” for roadway is presented, and the anchor cable and bolt parameters to check the design methods are also given. Finally, the proposed comprehensive support method “bolt + metal mesh + U-steel arch + shortcrete + grouting and cable” is used in the extension section of east main haulage roadway at −850 m level of Qujiang coal mine. The 173-day monitoring results show that the average convergence of sidewalls reaches 208 mm, and the average relative convergence of roof and floor reaches 448 mm, suggesting that this kind of support technology for controlling large deformation of high stress soft surrounding rock roadway is effective.