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In view of problem of floor heave failure in coal seam roadway, taking 53082 roadway of a mine as the research object, the stress state, displacement distribution and failure form of surrounding rock during the roadway excavation were analyzed and studied by UDEC discrete element simulation software. The results show that under relatively large horizontal tectonic stress, the weak coal seam of roadway floor 53082 becomes the main area of stress release, and the main failure characteristics are shallow tensile failure and deep shear failure. In view of problem that the original support scheme of roadway 53082 can not control the floor displacement and causes serious floor heave, a combined support mode of floor grouting and anchor bolt and cable was put forward through simulation analysis of support effect of different floor support schemes. The test results show that the combined support mode of floor grouting and anchor bolt and cable is superior to the single support mode of anchor bolt and cable, and greatly improves stress state of floor, and restrains the shear failure of deep floor, the displacement of roof and floor is controlled within 150 mm, the displacement of two sides is controlled within 60 mm, and the control effect of surrounding rock of roadway is better.

Indium (In) is a critical metal in liquid-crystal displays and solar panels. The Earth's crust has low In concentration in the order of 10 ng g−1, but it may be concentrated in sulphides by up to six orders of magnitude. Although In isotope studies may improve our understanding of the behaviour of In during different geological processes, such studies are limited for terrestrial samples. Here, we report a new method for In purification and high-precision isotope analysis for chemically different standards. A one-column method was used to separate In from the matrix with a recovery of 98% ± 2% (2SD). Indium concentrations and isotopic compositions were determined using the column eluate, and the results show large In isotope fractionation on desorbing In from the resin. Based on the mass balance, no significant In isotope fractionation was observed when In recovery is >93.8%. In terms of precision and accuracy of In isotopic compositions, the Ag-doping method was likely better than the standard–sample bracketing (SSB) method for correction of instrumental fractionation, with In uptake concentration down to 1 ng g−1 during isotope analysis. To ensure the accuracy of isotope analyses, the concentration match between the sample and standard should be within ±30%. An elemental doping study indicated that Na, K, Te, Sb, Pb, and Cu have no impact on the accuracy of In isotope analysis within the designated range; however, Ca/In, Mg/In, Cd/In and Sn/In ratios of >5, >20, >0.001 and >0.1, respectively, in sample solutions have significant impacts on In isotope analyses. Four international standards (BCR-2 basalt; J-Zn-1 sulphide; NIST-2711a soil; and OU-3 granite) and three in-house igneous rocks, purified using the developed method, had negligible isobaric interferences and matrix effect during In isotope analysis, demonstrating that the method can be used for terrestrial samples with different compositions. [ABSTRACT FROM AUTHOR]

Metal stable isotopes (e.g., Zn, Cd, and Cu) have been used to track metal sources in different types of hydrothermal systems. However, metal isotopic variations in sulphides could be triggered by various factors such as mineral precipitation and fluid mixing. Thus, tracking the metal sources of hydrothermal systems is still a big challenge for metal isotopes. In this study, we investigated the Cd isotopic systematics of sphalerite from the Nayongzhi Zn–Pb deposit, which is a Mississippi Valley‐type (MVT) deposit in the Sichuan–Yunnan–Guizhou mineralization province (SYGMP). We reinterpreted the published S isotope data for the SYGMP and found that the large S isotopic variations were controlled by Rayleigh fractionation between sulphide and reduced S. As such, a model that involves mixing of a metal‐rich fluid with a reduced S pool formed by thermochemical sulfate reduction (TSR) can explain the ore formation in the Nayongzhi deposit. Based on this model, no Cd isotopic fractionation was observed due to its low solubility in fluids during mixing, and thus the Cd isotopic variations of sphalerite were inherited from the source rocks. The large range of Zn/Cd ratios and uniform Cd isotopic compositions of the sulphides are similar to those of igneous rocks but different from those of sedimentary rocks, indicating that Zn and Cd were derived mainly from basement rocks (e.g., migmatite, gneiss, and granulite). Our results reaffirm that metal stable isotopes, particularly Cd isotope compositions of sphalerite, are powerful geochemical tracers for investigating the formation mechanisms of ore deposits. Plain Language Summary: Metal stable isotopes, particularly Cd isotopes, have been widely used in investigating the metal sources, fluid evolution, and formation mechanisms of ore deposits. Here, we studied the Cd isotopic compositions of sphalerite from the Nayongzhi Zn–Pb deposit in the Sichuan–Yunnan–Guizhou mineralization province. The range of δ114/110CdNIST‐3108 value is smaller in the Nayongzhi deposit (−0.16–0.21‰), but the published S isotopic composition has significant variation (11.8–33.0‰). We found that the large S isotopic variations were controlled by Rayleigh fractionation between sulphide and reduced S. Thus, a mineralization model of the Nayongzhi deposit has been proposed, which involves the mixing of a metal‐rich fluid with a reduced S pool formed by thermochemical sulfate reduction. Based on this model, no Cd isotopic fractionation was observed due to its low solubility in fluids during mixing. Therefore, the Cd isotopic variations of sphalerite were inherited from the source rocks. Combining the Zn/Cd ratios and Cd isotopic composition characteristics of the sulphides, igneous rocks, and sedimentary rocks, it is indicated that Zn and Cd were derived mainly from basement rocks (e.g., migmatite, gneiss, and granulite). Key Points: S isotopic variations caused by Rayleigh fractionation between sulphide and reduced S; Cd isotopic variations inherited from source rocksZn/Cd ratios and Cd isotopic compositions reveal that Zn and Cd were dominantly derived from basement rocksThe Nayongzhi deposit was formed by mixing between metal‐rich and reduced sulfur ore‐forming fluids [ABSTRACT FROM AUTHOR]

Purposes Rapid industrial development has led to increased levels of chlorophenolic pollutants in water bodies, which poses threats to ecosystems and human survival. Methods In order to efficiently degrade the refractory contaminant 2, 4-dichlorophenol (2, 4-DCP) in industrial wastewater, a Co3O4-coated carbon fiber catalyst (Co3O4@CF) with poor/rich electron-active centers was prepared by one-step impregnation method, and applied to the study of activated persulfate degradation of 2, 4-DCP. Findings The results show that Co3O4 is uniformly coated on the surface of carbon fibers with regular skeleton structure, and electron-rich cobalt centers and electron-poor carbon centers are formed under the Co(Ⅱ)-π interactions. Under the initial conditions of pH 3.0～7.8, 2, 4-DCP mass concentration of 50 mg/L, Co3O4@CF mass concentration of 0.1 g/L, and PMS concentration of 10 mmol/L, the complete degradation of 2, 4-DCP is achieved by Co3O4@CF within 20 min. During the process, Co3O4@CF can induce the transfer of electrons from electron-poor to electron-rich centers in the reaction system to achieve rapid reduction of Co3＋ and rapid activation of PMS. The characterization results further demonstrate that carbon fibers can not only at as carriers, but also participate in the PMS activated chain radical reaction through their structural defects, thus promoting the conversion of SO4-· to 1O2 and O2-· for the efficient degradation of 2, 4-DCP.

In the current research on the fatigue state of controllers using radiotelephony communication, most of them only consider the changes of voice in the time domain or frequency domain, while ignore that fatigue will affect the time domain and frequency domain at the same time. The voice of radiotelephony communication in the three fatigue states is converted into speech spectrum images that can reflect the characteristics of both the time domain and frequency domain, and the grayscale co-existence matrix is used to extract the typical feature parameters in four dimensions. The changes of the characteristic parameters of the controllers in different states are compared, and the controller fatigue detection model is constructed to detect the input features. The results show that the detection accuracy of using the spectrogram features combined with the traditional features as the input features is the highest(95.49%), which is 4% higher than that of the traditional features alone. The change of controllers fatigue state can intuitively reflected on the spectrogram and haves an impact on its eigenvalues, and the better detection results can be obtained by using this influence to detect the controllers fatigue state.

In this study, the mechanical properties of non-crimp fabric (NCF) composite laminates under low-velocity impact and compression after impact (CAI) tests were studied by Scanning electron microscopy (SEM) and Digital image correlation (DIC) techniques. The impact response under different impact times, impact angles, and impact distance is studied. Similarly, in CAI test, DIC technique is used to reveal the whole process of NCF composite compression failure, and SEM is used to reveal the microscopic failure form. The experimental results show that the impact damage process of NCF composites has strong directivity. The concrete manifestation is that the internal failure will extend along the paving direction at the failure layer. The peak load generated under 20 J impact energy is about 1/2 of that under 40 J impact energy. The impact distance is one of the important factors affecting the coupling effect of multiple impacts, and the impact angle has little effect on the internal damage extension. The proportion of internal damage area also supports the relevant view, that is, the average difference in the proportion of internal damage area under different impact distance is about 5%, while the average difference in the proportion of internal damage area under different impact angles is about 3%. During the compression process, the main failure mode is shear failure and the failure mode is brittle fracture. The oblique fracture occurs only when the oblique is 45° and the impact distance is large (50 mm). The impact angle has little effect on the residual compression performance of NCF.

Fretting fatigue failure of 2024 aluminum alloy under alternating normal load was investigated. A biaxial fretting fatigue test system is designed which can apply alternating phase load and distal load. Through Abaqus finite element analysis, the normal loading device of the test bench was analyzed and calculated, and the influence of the force conduction error and the swing angle of the fretting pad on the test accuracy was investigated, the accuracy of loading test machine is verified. The influence of phase difference of 0°, 45° and 90° on fatigue life of 2024 aluminum alloy under alternating normal load was studied. The test results show that the life of 2024 aluminum alloy specimens increases with the increase of phase difference. Through the analysis of wear state, it is found that the influence of wear is small when the phase difference is 0° and 45°, and the life increases with the increase of phase difference. When the phase difference is 90°, the wear is more serious. Under the joint action of wear and fatigue damage, the fatigue life of specimens at 90° phase difference is further increased. The overall trend of fretting fatigue life of specimens under alternating normal load is that the life increases with the increase of phase difference, and the wear increases with the increase of phase difference.

As an intravenous anesthetic, propofol has been indicated to induce neurotoxicity in both animal and human brains. It is of great significance to better understand the potential mechanism of propofol-induced neurotoxicity to eliminate the side effects of propofol. Esketamine is a sedative that has been proven to have an antidepressant effect. However, its effect on propofol-induced neurotoxicity and the underlying mechanism remain unclear. Herein, we investigated the role of esketamine in propofol-induced brain injury. A rat model of propofol-induced brain injury was established with or without the treatment of esketamine. The results demonstrated that propofol-induced impairment in spatial learning and memory of rats and promoted oxidative stress, neuronal injury and apoptosis in rat hippocampal tissues. The effects caused by propofol were attenuated by esketamine. Esketamine activated the mature brain-derived neurotrophic factor/tropomyosin receptor kinase B/phosphatidylinositide 3-kinase (mBDNF/TrkB/PI3K) signaling pathway in propofol-administrated rats. Moreover, knocking down BDNF partially reversed esketamine-mediated activation of the mBDNF/TrkB/PI3K signaling pathway and inhibition of neuronal apoptosis in propofol-induced rats. Overall, esketamine mitigates propofol-induced cognitive dysfunction and brain injury in rats by activating mBDNF/TrkB/PI3K signaling.

The three coordinate measuring machine (CMM) are increasingly widely used, but because of their high price, not easy to portable and other drawbacks, it is difficult to be widely used in university teaching procedures. Therefore, some disciplines such as measurement and control theories, measurement methods behind of the CMM are hard to well understood, which require students to have strong engineering ability. In order to solve the problem, the paper presents a virtual CMM way to improve the students engineering experience that improve the quality of course teaching as an assist tool. Firstly, use 3ds Max to model CMM, including probe, guide rail, frame, etc. Secondly,after the modeling development is completed, Hololens is used as a platform to develop scene interaction functions using Unity and c# scripts, that is, the connection between virtual scenes and students.Thirdly, in the virtual interface, students control the probe by the button to record and measure the coordinates of the object to be measured, and complete the measurement experiment. Students can master the measuring principle and measuring process of CMM faster through Hololens. So that students have a more intuitive understanding of CMM and are no longer limited by the traditional CMM teaching, it is of great significance to the cultivation of students’ engineering ability.