Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples

Study of the Effect of Gas Baffles on the Prevention and Control of Gas Leakage and Explosion Hazards in aUtility Tunnel

This paper takes the gas cabin in the utility tunnel in the Xuwei District of Lianyungang as the study object. Based on the computational fluid dynamics (CFD) theory, a simulation model of the gas cabin in the utility tunnel is established. The propagation law of methane leakage and diffusion and the characteristics of methane explosion shock wave propagation were simulated under different conditions of the gas cabin. These conditions are the presence or absence, spacing and height of the air baffle. The results show that: (1) the gas baffle can limit the propagation of methane at the top of the gas cabin and slow down the velocity of diffusion so as to increase the concentration of methane near the baffle and speed up the time for the monitor to reach the alarm concentration; (2) the first peak pressure and the second peak pressure generated in the middle of the gas cabin are smaller than that when the gas baffle is installed. The gas baffle has the function of blocking the propagation of shock waves. However, due to the installation of the gas baffle, the superposition of the shock wave will make the pressure surge at the gas baffle; and (3) combined with the simulation results, it is recommended that the gas baffle spacing is not less than 50 m and the height setting is not greater than 0.5 m

Effect of Gas on Burst Proneness and Energy Dissipation of Loaded Coal: An Experimental Study Using a Novel Gas-Solid Coupling Loading Apparatus

Deep coal mining is seriously affected by a combined dynamic disaster of rock burst and coal and gas outburst, but the influence mechanism of gas on this combined dynamic disaster is still not very clear, which is significantly different from the single type disasters. In this study, to explore the effect of gas on the coal-rock burst, a novel gas-solid coupling loading apparatus is designed to realize gas adsorption of coal sample with burst proneness and provide uniaxial loading environment under different gas pressure. A series of uniaxial compression tests of gas-containing coal with different gas pressure is carried out, and the energy dissipation process is monitored by an acoustic emission (AE) system. Results show that the macroscopic volume strain of the coal sample increases as gas adsorption and gas pressure increase under constant uniaxial loading pressure. Gas has the ability to expand the pores and natural fractures in coal sample by mechanical and physicochemical effects, which leads to a degradation in microstructure integrity of coal sample. With the increase of gas pressure, both the macrouniaxial compression strength (UCS) and elastic modulus show a downward trend; the UCS and elastic modulus of coal samples with 2 MPa gas pressure reduce by 58.78% and 48.82%, respectively, compared to those of the original coal samples. The main reason is that gas changes the pore-fissure structure and the mesoscopic stress environment inside the coal sample. Owing to the gas, the accumulated elastic energy of the gas-containing coal samples before failure reduces significantly, whereas the energy dissipated during loading increases, and the energy release process in the postpeak stage is smoother, indicating the participation of gas weakens the burst proneness of the coal sample. This study is of important scientific value for revealing the mechanism of combined dynamic disaster and the critical occurrence conditions of coal-rock burst and coal and gas outburst

Using gait videos to automatically assess anxiety

Background: In recent years, the number of people with anxiety disorders has&nbsp;increased worldwide. Methods for identifying anxiety through objective clues are&nbsp;not yet mature, and the reliability and validity of existing modeling methods have&nbsp;not been tested. The objective of this paper is to propose an automatic anxiety&nbsp;assessment model with good reliability and validity. Methods: This study collected 2D gait videos and Generalized Anxiety Disorder&nbsp;(GAD-7) scale data from 150 participants. We extracted static and dynamic time-domain features and frequency-domain features from the gait videos and used&nbsp;various machine learning approaches to build anxiety assessment models. We&nbsp;evaluated the reliability and validity of the models by comparing the influence of&nbsp;factors such as the frequency-domain feature construction method, training data&nbsp;size, time-frequency features, gender, and odd and even frame data on themodel. Results: The results show that the number of wavelet decomposition layers has&nbsp;a significant impact on the frequency-domain feature modeling, while the size of&nbsp;the gait training data has little impact on the modeling e ect. In this study, the&nbsp;time-frequency features contributed to the modeling, with the dynamic features&nbsp;contributingmore than the static features.Ourmodel predicts anxiety significantly&nbsp;better in women than inmen (rMale = 0.666, rFemale = 0.763, p &lt; 0.001). The best&nbsp;correlation coe cient between the model prediction scores and scale scores for all participants is 0.725 (p &lt; 0.001). The correlation coe cient between themodel&nbsp;prediction scores for odd and even frame data is 0.801&sim;0.883 (p &lt; 0.001).&nbsp; Conclusion: This study shows that anxiety assessment based on 2D gait video modeling is reliable and e ective. Moreover, we provide a basis for the&nbsp;development of a real-time, convenient and non-invasive automatic anxiety&nbsp;assessment method.</p

Volatile Profiling and Transcriptome Sequencing Provide Insights into the Biosynthesis of α-Pinene and β-Pinene in <i>Liquidambar formosana</i> Hance Leaves

Liquidambar formosana Hance is a pinene-rich deciduous plant species in the Altingiaceae family that is used as a medicinal plant in China. However, the regulatory mechanisms underlying α-pinene and β-pinene biosynthesis in L. formosana leaves remain unknown. Here, a joint analysis of the volatile compounds and transcriptomes of L. formosana leaves was performed to comprehensively explore the terpene synthase (TPS) that may participate in α-pinene and β-pinene biosynthesis. Headspace solid-phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS) jointly detected volatile L. formosana leaves. Trees with high and low levels of both α-pinene and β-pinene were defined as the H group and L group, respectively. RNA sequencing data revealed that DXR (1-deoxy-D-xylulose-5-phosphate reductoisomerase), HDS [(E)-4-hydroxy-3-methylbut-2-eny-l-diphosphate synthase], and TPS may be the major regulators of monoterpenoid biosynthesis. We identified three TPSs (LfTPS1, LfTPS2, and LfTPS3), which are highly homologous to α-pinene and β-pinene synthases of other species in phylogenetic analysis. Four TPS genes (LfTPS1, LfTPS2, LfTPS4, LfTPS5) may be critically involved in the biosynthesis and regulation of α-pinene and β-pinene in L. formosana. Bioinformatic and transcriptomic results were verified using quantitative real-time PCR. We identified LfTPS1, LfTPS2 as candidate genes for α-pinene and β-pinene biosynthesis that significantly improve the yield of beneficial terpenoids