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Experimental and numerical investigation on failure characteristics and mechanism of coal with different water contents

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International Journal of Coal Science & Technology 2023年第4期10卷 325-342页

作者： Xuewei Liu Haixiao Chen Bin Liu Sai Wang Quansheng Liu Yong Luo Jin luo State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China Faculty of Engineering China University of GeosciencesWuhan 430074China Ping’an Mining Engineering Technology Research Institute Co. Ltd.Huainan 232001China

Water injection, as a widely used technique to prevent coal burst, can restrain the fractured coal seam and released the energy storage. In this study, laboratory tests were frstly carried out on standard coal specimens with fve diferent water contents (i.e., 0%, 0.6%, 1.08%, 1.5%, 2.0%, and 2.3%). The failure mode, fragment size, and energy distribution characteristics of coal specimens were investigated. Experimental results show that strength, elastic strain energy, dissipated energy, brittleness index, as well as impact energy index decrease with increasing water content. Besides, the failure mode transitions gradually from splitting ejection to tensile-shear mixed failure mode as water content increases, and average fragment size shows positively related to water content. Moreover, scanning electron microscope tests results indicate that water in coal sample mainly causes the mineral softening and defects increase. Furthermore, a numerical model containing roadway excavation was established considering the water on coal burst prevention. Modelling results revealed that water injection can reduce degree of coal burst and ejection velocity of coal blocks, while it will raise up the depth of crack zone and surface displacement of roadway. Combined with laboratory tests and numerical results, the micro mechanism, energy mechanism, and engineering signifcance of water injection on coal burst prevention were fnally analyzed.

关键词： Water content Coal burst Failure mode Energy Numerical simulation

On Solution Sequences of the Singular Liouville Equations with an Integral Constraint

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Acta Mathematica Sinica,English Series 2014年第1期30卷 133-150页

作者： Yong Luo Mathematisches Institut Albert-Ludwigs-Universitat Freiburg

In this paper,we analyze the blow-up behavior of sequences{uk}satisfying the following conditionsΔuk=｜x｜2αk V k eukinΩ,（0.1）whereΩR2,V k→V in C1,｜Vk｜≤A,0

关键词： Singular Liouville equations blow up analysis integral constraint

Tribo-corrosion mechanisms and electromechanical behaviours for metal implants materials of CoCrMo,Ti6Al4V and Ti15Mo alloys

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Biosurface and Biotribology 2022年第1期8卷 44-51页

作者： Hongxiang Wang Jingjing Zheng Xiaolei Sun Yong Luo Jiangsu Vocational College of Electronics and Information Huai'anChina School of Materials Science and Physics China University of Mining&TechnologyXuzhouChina

Corrosion and wear play significant roles in the aseptic loosening of artificial hip joints for the long-term service.In this present study,tribo-corrosion tests were carried out through a reciprocating ball-on-plate system to evaluate the corrosion and wear prop-erties of CoCrMo,Ti6Al4V and Ti15Mo alloys in a simulated body fluid(SBF)solution.It was found that the tribo-corrosion behaviours of CoCrMo/Al_(2)O_(3)and Ti15Mo/Al_(2)O_(3)systems had significant wear-corrosion synergistic interaction,and wear-induced corro-sion was dominant.For Ti6Al4V/Al_(2)O_(3)systems,their wear mechanism under SBF lubrication was a combination of abrasive,adhesive and fatigue wear.While the wear mechanism of the Ti15Mo/Al_(2)O_(3)system under synergistic interaction was a combination of abrasive and adhesive wear.Finally,it was suggested that the Ti15Mo alloy would be the better alternative for metal implant applications compared with the CoCrMo alloy for the consideration of both wear and potential poisonous ions such as Co(III)and Cr(VI).

关键词： artificial joints biomaterials wear mechanisms

Influence of maximum principal stress direction on the failure process and characteristics of D-shaped tunnels

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International Journal of Mining Science and Technology 2022年第5期32卷 1125-1143页

作者： Linqi Huang Xuefeng Si Xibing Li Fengqiang Gong Yong Luo School of Resources and Safety Engineering Central South UniversityChangsha 410083China School of Resources Environment and Safety Engineering University of South ChinaHengyang 421001China School of Civil Engineering Southeast UniversityNanjing 211189China

To investigate the failure process and characteristics of D-shaped tunnels under different maximum principal stress directions θ, true-triaxial tests were conducted on cubic sandstone samples with a through D-shaped hole. The test results show that the failure process can be divided into 4 periods:calm, buckling deformation, gradual buckling and exfoliation of rock fragment, and formation of a Vshaped notch. With an increase in θ from 0° to 90°, the size of the rock fragments first decreases and then increases, whereas the fractal dimension of the rock fragments first increases and then decreases. Meanwhile, the failure position at the left side shifts from the sidewall to the corner and finally to the floor, whereas the failure position at the right side moves from the sidewall to the spandrel and finally to the roof, which is consistent with the failure position in underground engineering. In addition, the initial vertical failure stress first decreases and then increases. By comparing the results,the failure severities at different maximum principal stress directions can be ranked from high to low in the following order: 90°>60°>30°>45°>0°.

关键词： Deep D-shaped tunnel Rockburst Maximum principal stress direction True-triaxial test V-shaped notch

Improved Convolutional Neural Network for Traffic Scene Segmentation

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Computer Modeling in Engineering & Sciences 2024年第3期138卷 2691-2708页

作者： Fuliang Xu Yong Luo Chuanlong Sun Hong Zhao College of Mechanical and Electrical Engineering Qingdao UniversityQingdao266071China

In actual traffic scenarios,precise recognition of traffic participants,such as vehicles and pedestrians,is crucial for intelligent transportation.This study proposes an improved algorithm built on Mask-RCNN to enhance the ability of autonomous driving systems to recognize traffic participants.The algorithmincorporates long and shortterm memory networks and the fused attention module(GSAM,GCT,and Spatial Attention Module)to enhance the algorithm’s capability to process both global and local information.Additionally,to increase the network’s initial operation stability,the original network activation function was replaced with Gaussian error linear unit.Experiments were conducted using the publicly available Cityscapes dataset.Comparing the test results,it was observed that the revised algorithmoutperformed the original algorithmin terms of AP_(50),AP_(75),and othermetrics by 8.7%and 9.6%for target detection and 12.5%and 13.3%for segmentation.

关键词： Instance segmentation deep learning convolutional neural network attention mechanism

Improved uranium leaching efficiency from low-permeability sandstone using low-frequency vibration in the CO_(2)+O_(2) leaching process

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第3期14卷 770-780页

作者： yong Zhao yong Gao Caiwu luo Jun Liu School of Resource Environment and Safety Engineering University of South ChinaHengyang421001China Department of Nuclear Safety China Institute of Atomic EnergyBeijing100000China College of Humanities and Foreign Languages Xi’an University of Science and TechnologyXi’an710054China China Coal Technology Engineering Group Chongqing Research Institute Chongqing 400039China

Extraction of uranium from low-permeability sandstone is a long-standing challenge in mining.The improvement of sandstone permeability has therefore become a key research focus to improve the uranium leaching effect.To address the low-permeability problem and corresponding leaching limits,leaching experiments are performed using newly developed equipment that could apply low-frequency vibration to the sandstone samples.The test results indicate that low-frequency vibration significantly improves the uranium leaching performance and permeability of the sandstone samples.The leaching effect of low-frequency vibration treatment is approximately nine times more effective than ultrasonic vibration treatment,whereas the concentration of uranium ions generated without vibration treatment is not detectable.Mathematical model that considers the combined action of physico-mechanical vibration and chemical erosion is established to describe the effect of low-frequency vibration on the permeability.The calculated results are in good agreement with the tested permeability values.This study thus offers a new method to effectively leach more uranium from low-permeability sandstone using CO_(2)+O_(2)and provides an insight into the impact of low-frequency vibration on the uranium leaching process.

关键词： Uranium leaching Low-frequency vibration Chemical erosion Low permeability Permeability model

Numerical investigation on the tensile fracturing behavior of rock-shotcrete interface based on discrete element method

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International Journal of Mining Science and Technology 2020年第3期30卷 293-301页

作者： Jiadong Qiu Lin luo Xibing Li Diyuan Li Ying Chen Yong Luo Shenzhen Key Laboratory of Deep Underground Engineering Sciences and Green Energy Shenzhen UniversityShenzhen 518060China Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring Ministry of EducationCentral South UniversityChangsha 410083China School of Resources and Safety Engineering Central South UniversityChangsha 410083China Center of Rock Mechanics and Geohazards Shaoxing UniversityShaoxing 312000China

Four groups of numerical models of Brazilian tests on rock-shotcrete interfaces were successfully conducted by PFC2D. The tensile strength and Young’s modulus of shotcrete were considered. Six different undulations of rock-shotcrete interface were set up. The influences of multiple parameters on the bearing characteristics of the rock-shotcrete interface were studied. The results showed that a better support performance can be obtained by increasing the Young’s modulus of shotcrete rather than the tensile strength of shotcrete. For different tensile strength and Young’s modulus, the increase of sawtooth height has different effects on the support performance. The failure mechanism of the rock-shotcrete interfaces was analysed in detail. The stress shielding effect and stress concentration effect caused by the shape characteristics of rock-shotcrete interface were observed. The influence of these parameters on the overall support performance should be fully considered in a reasonable support design.

关键词： Tensile strength PFC Shotcrete Fracturing behavior Rock interface

Preparation of lithium carbonate by microwave assisted pyrolysis

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Chinese Journal of Chemical Engineering 2022年第12期52卷 146-153页

作者： Shen Wang Xiaokang Pei Yong Luo Guangwen Chu Haikui Zou Baochang Sun State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing 100029China Research Center of the Ministry of Education for High Gravity Engineering and Technology Beijing University of Chemical TechnologyBeijing 100029China

Investigations were conducted to purify crude Li_(2)CO_(3)via direct carbonation with CO_(2)at atmospheric pressure and pyrolysis with both water bath heating method and microwave heating method.The reaction kinetics of LiHCO_(3)pyrolysis was studied and the effect of different operating conditions including initial concentration of LiHCO_(3)solution,pyrolysis temperature and stirring speed on the purity of Li_(2)CO_(3)was investigated to obtain the optimal operating conditions.Results showed that the effect law is similar in the two pyrolysis processes.The purity of the Li_(2)CO_(3)increases firstly and then decreases with the increase of the initial concentration of LiHCO_(3)solution and the stirring speed,while the purity of Li_(2)CO_(3)first decreases and then increases with the increase of pyrolysis temperature.The product yield increases with the increase of initial concentration of LiHCO_(3)solution and pyrolysis temperature and is essentially unaffected by the stirring speed.Under the optimal operating conditions,the purity of Li_(2)CO_(3)can reach up to 99.86%and 99.81%in water bath heating and microwave heating process,respectively.In addition,the pyrolysis rate of microwave assisted pyrolysis is 6 times that of water bath heating process,indicating that the microwave heating technology can significantly improve pyrolysis efficiency and reduce energy consumption.

关键词： Lithium bicarbonate Pyrolysis process Traditional heating Microwave heating Product yield

Deep Learning for Seasonal Precipitation Prediction over China

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Journal of Meteorological Research 2022年第2期36卷 271-281页

作者： Weixin JIN Yong Luo Tongwen WU Xiaomeng HUANG Wei XUE Chaoqing YU Department of Earth System Science Ministry of Education Key Laboratory for Earth System ModelingInstitute for Global Change StudiesTsinghua UniversityBeijing 100084 Beijing Climate Center China Meteorological AdministrationBeijing 100081 AI for Earth Lab the Joint Laboratory of Cross-Strait Tsinghua Research InstituteXiamen 361006

Despite significant progress having been made in recent years,the forecast skill for seasonal precipitation over China remains limited.In this study,a deep-learning-based statistical prediction model for seasonal precipitation over China was developed.The model was trained to learn the distribution of the seasonal precipitation using simultaneous general circulation data.First,it was pre-trained with the hindcasts of several general circulation models(GCMs),and evaluation of the test set suggested that the pre-trained model could basically reproduce the GCM-predicted precipitation,with the anomaly pattern correlation coefficients(PCCs)greater than 0.80.Then,transfer learning was applied by using ECMWF Reanalysis v5(ERA5)data and gridded precipitation observational data over China,to further correct the systemic errors in the model.As a result,using general circulation fields from reanalysis as the input,this hybrid model performed reasonably well in simulating the seasonal precipitation over China,with the PCC reaching 0.71.In addition,the results using the circulation fields predicted by GCMs as the input were also assessed.In general,the proposed model improves the PCC over China by 0.10-0.13,as compared to the raw GCM outputs,for lead times of 1-4 months.This deep learning model has been used at the National Climate Center of China Meteorological Administration for the past two years to provide guidance for summer precipitation prediction over China and has performed extremely well.

关键词： seasonal precipitation seasonal prediction statistical downscaling deep learning