The mechanical behavior of coal is the key factor affecting underground coal mining and coalbed methane extraction.In this study,triaxial compression and seepage tests were carried out on coal at different gas pressur...The mechanical behavior of coal is the key factor affecting underground coal mining and coalbed methane extraction.In this study,triaxial compression and seepage tests were carried out on coal at different gas pressures.The mechanical properties and failure process of coal were studied,as well as the acoustic emission(AE)and strain energy.The influence of gas pressure on the mechanical parameters of this coal was analyzed.Based on the conventional energy calculation formula,the pore pressure was introduced through the effective stress formula,and each energy component of coal containing gas was refined innovatively.The contribution of gas pressure to the total energy input and dissipation during loading was quantitatively described.Finally,the influence of gas pressure on coal strength was theo-retically analyzed from the perspectives of MohreCoulomb criterion and fracture mechanics.The results show that the total absorbed energy comprises the absorbed energy in the axial pressure direction(positive)and in the confining pressure direction(negative),as well as that induced by the pore pressure(initially negative and then positive).The absorbed energy in the axial pressure direction accounts for the main proportion of the total energy absorbed by coal.The quiet period of AE in the initial stage shortens,and AE activity increases during the pre-peak stage under high gas pressure.The fractal characteristics of AE in three stages are studied using the correlation dimension.The AE process has different forms of self-similarity in various deformation stages.展开更多
目的比较不同剂量阿芬太尼对老年患者快速顺序诱导气管插管心血管反应的影响。方法选择2022年3—9月行气管插管全麻老年患者96例,男47例,女49例,年龄65~80岁,BMI 18~24 kg/m^(2),ASAⅠ或Ⅱ级。采用随机数字表法分为四组:阿芬太尼10μg/k...目的比较不同剂量阿芬太尼对老年患者快速顺序诱导气管插管心血管反应的影响。方法选择2022年3—9月行气管插管全麻老年患者96例,男47例,女49例,年龄65~80岁,BMI 18~24 kg/m^(2),ASAⅠ或Ⅱ级。采用随机数字表法分为四组:阿芬太尼10μg/kg组(A组)、阿芬太尼15μg/kg组(B组)、阿芬太尼20μg/kg组(C组)和阿芬太尼25μg/kg组(D组),每组24例。记录麻醉诱导前、气管插管后1、5 min的HR、MAP,同时抽取患者静脉血3 ml,检测血浆中去甲肾上腺素(NE)和皮质醇(Cor)的浓度、超声测量心脏指数(CI)、心脏射血分数(EF)。记录麻醉诱导后至气管插管后5 min高血压、低血压、心动过缓、心动过速的发生情况。结果与麻醉诱导前比较,A组和B组在气管插管后1、5 min HR明显增快,MAP、NE和Cor浓度明显升高,CI和EF明显降低(P<0.05);C组和D组气管插管后1 min HR明显增快,MAP明显升高,D组插管后5 min HR明显减慢,MAP、血浆NE和Cor浓度、CI和EF明显降低(P<0.05)。与A组比较,C组和D组气管插管后1、5 min HR明显减慢,血浆NE和Cor浓度明显降低,气管插管后1 min CI和EF明显升高,高血压和心动过速发生率明显降低(P<0.05);D组插管后5 min CI和EF明显降低,低血压和心动过缓发生率明显升高(P<0.05)。结论阿芬太尼20μg/kg用于老年患者快速顺序诱导气管插管,可有效抑制插管引起的剧烈心血管反应,同时避免心血管系统的抑制,血流动力学更平稳。展开更多
The lack of research on the effect of diffusion on methane extraction leads to low methane concentration and low utilization.The Comsol Multiphysics software is used to solve the numerical gas and solid coupled model ...The lack of research on the effect of diffusion on methane extraction leads to low methane concentration and low utilization.The Comsol Multiphysics software is used to solve the numerical gas and solid coupled model which considers the diffusion of coal matrix,fracture seepage,permeability evolution and coal deformation.The simulation results reveal the effect of diffusion process on methane migration.The gas diffusion rate is relatively high in the initial stage.With the increase in time,the difference between coal fractures and coal matrix blocks becomes lower and the gas diffusion rate decreases gradually.The gas seepage rate decreases significantly near the borehole and the decrease degree becomes small when it is far away from borehole.The influence of diffusion time on gas drainage rate is not obvious.展开更多
基金This study is sponsored by the National Natural Science Foun-dation of China(Grant No.12002270)the China Postdoctoral Science Foundation(Grant Nos.2021T140553 and 2021M692600).
文摘The mechanical behavior of coal is the key factor affecting underground coal mining and coalbed methane extraction.In this study,triaxial compression and seepage tests were carried out on coal at different gas pressures.The mechanical properties and failure process of coal were studied,as well as the acoustic emission(AE)and strain energy.The influence of gas pressure on the mechanical parameters of this coal was analyzed.Based on the conventional energy calculation formula,the pore pressure was introduced through the effective stress formula,and each energy component of coal containing gas was refined innovatively.The contribution of gas pressure to the total energy input and dissipation during loading was quantitatively described.Finally,the influence of gas pressure on coal strength was theo-retically analyzed from the perspectives of MohreCoulomb criterion and fracture mechanics.The results show that the total absorbed energy comprises the absorbed energy in the axial pressure direction(positive)and in the confining pressure direction(negative),as well as that induced by the pore pressure(initially negative and then positive).The absorbed energy in the axial pressure direction accounts for the main proportion of the total energy absorbed by coal.The quiet period of AE in the initial stage shortens,and AE activity increases during the pre-peak stage under high gas pressure.The fractal characteristics of AE in three stages are studied using the correlation dimension.The AE process has different forms of self-similarity in various deformation stages.
文摘目的比较不同剂量阿芬太尼对老年患者快速顺序诱导气管插管心血管反应的影响。方法选择2022年3—9月行气管插管全麻老年患者96例,男47例,女49例,年龄65~80岁,BMI 18~24 kg/m^(2),ASAⅠ或Ⅱ级。采用随机数字表法分为四组:阿芬太尼10μg/kg组(A组)、阿芬太尼15μg/kg组(B组)、阿芬太尼20μg/kg组(C组)和阿芬太尼25μg/kg组(D组),每组24例。记录麻醉诱导前、气管插管后1、5 min的HR、MAP,同时抽取患者静脉血3 ml,检测血浆中去甲肾上腺素(NE)和皮质醇(Cor)的浓度、超声测量心脏指数(CI)、心脏射血分数(EF)。记录麻醉诱导后至气管插管后5 min高血压、低血压、心动过缓、心动过速的发生情况。结果与麻醉诱导前比较,A组和B组在气管插管后1、5 min HR明显增快,MAP、NE和Cor浓度明显升高,CI和EF明显降低(P<0.05);C组和D组气管插管后1 min HR明显增快,MAP明显升高,D组插管后5 min HR明显减慢,MAP、血浆NE和Cor浓度、CI和EF明显降低(P<0.05)。与A组比较,C组和D组气管插管后1、5 min HR明显减慢,血浆NE和Cor浓度明显降低,气管插管后1 min CI和EF明显升高,高血压和心动过速发生率明显降低(P<0.05);D组插管后5 min CI和EF明显降低,低血压和心动过缓发生率明显升高(P<0.05)。结论阿芬太尼20μg/kg用于老年患者快速顺序诱导气管插管,可有效抑制插管引起的剧烈心血管反应,同时避免心血管系统的抑制,血流动力学更平稳。
基金This study is sponsored by the National Natural Science Foundation of China(no.51679199)the Initiation Fund of Doctor’s Research(no.107-451117008)+1 种基金the Special Funds for Public Industry Research Projects of the Ministry of Water Resources(no.201501034-04 and 201201053-03)the Key Laboratory for Science and Technology Coordination&Innovation Projects of Shaanxi Province(no.2014SZS15-Z01).References。
文摘The lack of research on the effect of diffusion on methane extraction leads to low methane concentration and low utilization.The Comsol Multiphysics software is used to solve the numerical gas and solid coupled model which considers the diffusion of coal matrix,fracture seepage,permeability evolution and coal deformation.The simulation results reveal the effect of diffusion process on methane migration.The gas diffusion rate is relatively high in the initial stage.With the increase in time,the difference between coal fractures and coal matrix blocks becomes lower and the gas diffusion rate decreases gradually.The gas seepage rate decreases significantly near the borehole and the decrease degree becomes small when it is far away from borehole.The influence of diffusion time on gas drainage rate is not obvious.
