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1

Energy distribution law of coal–rock combined body under confining pressure effect

Chen Guangbo, Zhang Jing, Li Yuan, Liu Fengxu, Li Tan, Zhang Guohua

Acta Geophysica

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2023

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Vol. 71, no. 4

1831--1843

EN

Coal measure strata are composed of many kinds of rock layers with different properties, and the energy accumulation ability of each rock layer is different, which causes the uneven distribution of energy. In order to explore the accumulation layer of rock burst energy in coal–rock system, based on the structural characteristics and mechanical properties of coal and rock, the mechanical model of coal–rock combined body was constructed, and the calculation formula of energy distribution of coal–rock combined body was deduced. The axial compression tests of coal–rock combined body under five confining pressures (0, 5, 10, 15 and 20 MPa) were designed and carried out. The results show that: 1) Under five confining pressures, the average compressive strength of the specimens was 18.74 MPa, 20.75 MPa, 24.68 MPa, 28.02 MPa and 32.05 MPa, respectively. With the increase in confining pressure, the compressive strength also increased linearly; 2) Under the five confining pressures, the pre-peak accumulated energy of the specimens was 0.106 kJ, 0.244 kJ, 0.591 kJ, 0.758 kJ and 1.602 kJ. With the continuous increase in the confining pressure, the pre-peak accumulated energy increased exponentially; 3) With the increase in confining pressure, the coal component accumulation energy increased exponentially, followed by 0.069 kJ, 0.182 kJ, 0.440 kJ, 0.630 kJ and 1.419 kJ, and the proportion of coal component accumulation energy was 65.14%, 71.63%, 76.72%, 82.89% and 87.07%, respectively, which were all greater than 50%. Combined bodies accumulated more energy under loading conditions, most of which were accumulated on coal components, and coal components were the main carriers of energy accumulation, which played a leading role in the destruction of combined bodies; 4) The energy distribution test method was discussed and analyzed. The energy distribution test method of coal–rock combined body based on single specimen method could effectively avoid the influence of size effect and coal–rock individual difference on energy accumulation. At the same time, the test time was shortened, the test workload was reduced, and the calculation accuracy was improved; 5) The rationality and reliability of the two methods for direct and indirect determination of coal–rock component energy were demonstrated. The error rates of the two methods were 2.936%, 1.846%, 3.125%, 3.412% and 0.862%, which were less than 5%. The error had little effect on the test results. The research results have reference significance for exploring the key strata of rock burst energy accumulation and the precise prevention and control of rock burst.

2

Texture Representation and Application of Colored Spun Fabric Using Uniform Three-Structure Descriptor

Li Yuan, Muli Liu, Liu JunPing, Yang Yali, Gong Xue

Autex Research Journal

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2022

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Vol. 22, no. 4

477--487

EN

The local binary pattern (LBP) and its variants have shown their effectiveness in texture images representation. However, most of these LBP methods only focus on the histogram of LBP patterns, ignoring the spatial contextual information among them. In this paper, a uniform three-structure descriptor method was proposed by using three different encoding methods so as to obtain the local spatial contextual information for characterizing the nonuniform texture on the surface of colored spun fabrics. The testing results of 180 samples with 18 different color schemes indicate that the established texture representation model can accurately express the nonuniform texture structure of colored spun fabrics. In addition, the overall correlation index between texture features and sample parameters is 0.027 and 0.024, respectively. When compared with the LBP and its variants, the proposed method obtains a higher representational ability, and simultaneously owns a shorter time complexity. At the same time, the algorithm proposed in this paper enjoys ideal effectiveness and universality for fabric image retrieval. The mean Average Precision (mAP) of the first group of samples is 86.2%; in the second group of samples, the mAP of the sample with low twist coefficient is 89.6%, while the mAP of the sample with high twist coefficient is 88.5%.

3

Deterioration law of intermittent jointed sandstone mechanical properties under water-rock interaction

Chen Guangbo, Li Yuan, Li Tan, Zhang Guohua

Acta Geophysica

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2022

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Vol. 70, no 4

1923--1935

EN

In water-rich mines, water conservancy, and hydropower projects, the rock mass is immersed in water for a long time, which leads to changes in its mechanical properties and affects the safety and stability of the engineering rock mass. Based on the long-term immersion of rock mass with intermittent joints by water, uniaxial compression tests were carried out on prefabricated intermittent jointed sandstone with five inclinations (0°, 30°, 45°, 60°, 90°) and three connectivity ratios (0.25, 0.50, 0.75) under different immersion times to study sandstone with intermittent joints’ mechanical response and deterioration mechanism. The research shows that: (1) With the increase of the joint inclination, the compressive strength and elastic modulus of the sandstone with intermittent joints first decreased and then increased, showing a U-shaped distribution. The compressive strength and elasticity of the sample with an inclination of 60° reach the minimum value; at the initial stage of immersion, the deterioration effect of the sample is more significant, and the deterioration effect decreases gradually with the increase in immersion time; in the initial stage of water immersion, the deterioration effect of the sample is more significant, and with the increase of the immersion time, the deterioration effect gradually weakens. (2) Immersion time and joint inclination have a great influence on the included angle, number, and mode of failure cracks. With the increase in immersion time, the plastic characteristics of the sample increase obviously, showing the characteristics of loose and weak; with the increase in joint inclination, the failure mode of the sample gradually changes from tension failure to tension shear failure, and tension failure. The influence degree of joints on failure is weak-induction-control-induction. (3) Under the water–rock action, the cement between mineral particles of the sample is gradually dissolved, the cementation of mineral particles is weakened, and the mineral particles develop into layered and fake structure, which gradually evolves from dense structure to porous loose structure. (4) The deterioration mechanism of the mechanical properties of the sandstone with intermittent joints under the water–rock action was analyzed from the perspectives of physics, chemistry, and mechanics. The deterioration of the mechanical properties of the sample is a process of gradual accumulation of damage.

4

Determination of acrylamide in foods by automatic accelerated solvent extraction and gas chromatography-mass spectrometry

Kang Cuicui, Ma Haijian, Li Yuan, Zhang Chizhong, Hong Yueqin, Shao Minghua

Acta Chromatographica

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2021

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Vol. 33, no. 1

64--72

EN

The aim of the experiment is to establish a method for the determination of acrylamide in food by automatic accelerated solvent extraction-gas chromatography-mass spectrometry. D3-acrylamide was used as isotope internal standard, crushed samples were extracted and purified by automatic accelerated solvent, acrylamide was derivatized into 2,3-dibromopropanamide by potassium bromide and potassium bromate under acidic conditions, and then the derivative was extracted by ethyl acetate and detected by gas chromatography-mass spectrometry. The method had a good linear relationship in the concentration range of 10–2000 ng/mL, and the coefficient of determination (R2) was 0.9997. The detection limit of the method was 3 mg/kg. The quantification limit of the method was 10 mg/kg. The standard addition recovery of acrylamide was between 105 and 120%, and the relative standard deviation of the recovery of acrylamide was less than 3.0%. The experimental result showed that the method was simple, sensitive, efficient and accurate, and could be used for the determination of acrylamide in food.

5

Characteristics and metal leachability of natural contaminated soil under acid rain scenarios

Tan Wenfa, Li Yuan, Ding Lei, Wang Yachao, Li Jiangxiang, Deng Qinwen, Guo Feng, Xiao Xue

Archives of Environmental Protection

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2019

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Vol. 45, no. 2

91--98

EN

Contamination of soil with heavy metals has become a worldwide environmental problem, and receives great attention. In this study, we aim to investigate soil pollution level affected by an industrial district nearby. The total amount of typical heavy metals in the soils (Hengyang Songmu Industrial Park, Hunan Province, China) was analyzed. In addition, the fraction analysis and laboratory simulation leaching via different pH rainwater was carried out to study the migration and transformation of heavy metals. The main results show that the contents of Cu, Zn, Pb, Cr and Cd in the samples were higher than the soil background values in Hunan Province. The heavy metals forms, analyzed by sequential extraction method, show that the proportion of the unstable form of Cd, Zn and Pb was more than 50%. Igeo values indicate that the heavy metal pollution degree of soil sample #5 at the investigated area is recorded in the order of Cd(6.42), Zn(2.28), Cu(1.82), Pb(1.63), and Cr(0.37). Cu, Zn, Pb, Cr and Cd in this area could pose a potential leaching risk to the environment which may affect the food chain and constitute a threat to human health. It would be necessary to take steps to stabilize and monitor the heavy metals in soil.