The damage and failure law of rock mass with holes is of great significance to the stability control of roadways. This study investigates the mechanical properties and failure modes of porous rock masses under cyclic ...The damage and failure law of rock mass with holes is of great significance to the stability control of roadways. This study investigates the mechanical properties and failure modes of porous rock masses under cyclic loading, elucidates the acoustic emission (AE) characteristics and their spatial evolution, and establishes the interrelation among AE, stress, strain, time, and cumulative damage. The results reveal that the rock mass with holes and the intact rock mass show softening and hardening characteristics after cyclic loading. The plastic strain of the rock mass with holes is smaller than that of the intact rock mass, and the stress −strain curve shows hysteresis characteristics. Under uniaxial compression, the pore-bearing rock mass shows the characteristics of higher ringing count, AE energy, b-value peak, and more cumulative ringing count in the failure stage, while it shows lower characteristics under cyclic action. At the initial stage of loading, compared with the intact rock mass, the pore-containing rock mass shows the characteristics of a low b-value. The AE positioning and cumulative damage percentage are larger, and the AE positioning is denser around the hole. The specimen with holes is mainly shear failure, and the complete specimen is mainly tensile shear failure.展开更多
射频四极场(Radio frequency quodrupole,RFQ)加速器是一种非常适于用作MeV级能量离子注入的加速器。它具有束流强、体积小、使用方便、离子源处在地电位,还可同时加速正、负两种离子等优点。本文介绍了RFQ加速器在国际上的发展状况及...射频四极场(Radio frequency quodrupole,RFQ)加速器是一种非常适于用作MeV级能量离子注入的加速器。它具有束流强、体积小、使用方便、离子源处在地电位,还可同时加速正、负两种离子等优点。本文介绍了RFQ加速器在国际上的发展状况及其基本原理、北京大学研制的1 MeV RFQ加速器的具体结构、性能以及一种新型RFQ-SFRFQ组合加速器的特点。展开更多
目的探讨阵发性心房颤动(PAF)患者左心房功能联合B型脑钠肽(BNP)预测环肺静脉射频消融术(CPVA)后复发的意义。方法选取2017年1月至2018年12月在常州市第一人民医院住院的拟行第一次CPVA术的PAF患者201例。CPVA术前测定患者血液BNP水平;...目的探讨阵发性心房颤动(PAF)患者左心房功能联合B型脑钠肽(BNP)预测环肺静脉射频消融术(CPVA)后复发的意义。方法选取2017年1月至2018年12月在常州市第一人民医院住院的拟行第一次CPVA术的PAF患者201例。CPVA术前测定患者血液BNP水平;实时三维超声心动图(RT-3DE)获取左心房时间-容积曲线;根据术后3个月动态心电图结果,将PAF患者分为窦性心律组和复发组。应用多因素Logistic回归分析影响CPVA术后PAF复发的独立危险因素;对获得的独立危险因素行预测PAF复发的ROC曲线,比较不同指标的效能。结果201例PAF患者完成CPVA术,随访中36例(17.9%)复发,复发组BNP高于窦性心律组(P<0.05)。2组间左心房最大容积指数(LAVImax)、左心房最小容积指数(LAVImin)差异有统计学意义(均P<0.05);2组间膨胀指数(EI)、舒张期射血指数(DEI)、被动射血指数(PEI)、主动射血指数(AEI)差异均有统计学意义(均P<0.05)。多因素Logistic回归分析表明:术前BNP、DEI及PAF病史是PAF复发的独立预测因素(均P<0.05)。ROC曲线显示:DEI及联合指标(DEI+BNP)预测CPVA术后复发的效能均优于LAVImin(AUC:0.881 vs 0.686、0.901 vs 0.686,均P<0.05);联合诊断的特异性优于DEI及BNP(89.7%vs 79.4%、89.7%vs 72.7%,均P<0.05)。结论CPVA术治疗的PAF患者中,左心房存储功能受损及BNP增高均是CPVA术后PAF复发的独立预测因素,两者联合可提高预测复发的特异度。展开更多
基金Projects(U22A20165, 52004289) supported by the National Natural Science Foundation of ChinaProjects(2022XJNY01, BBJ2024001) supported by the Fundamental Research Funds for the Central Universities,China。
文摘The damage and failure law of rock mass with holes is of great significance to the stability control of roadways. This study investigates the mechanical properties and failure modes of porous rock masses under cyclic loading, elucidates the acoustic emission (AE) characteristics and their spatial evolution, and establishes the interrelation among AE, stress, strain, time, and cumulative damage. The results reveal that the rock mass with holes and the intact rock mass show softening and hardening characteristics after cyclic loading. The plastic strain of the rock mass with holes is smaller than that of the intact rock mass, and the stress −strain curve shows hysteresis characteristics. Under uniaxial compression, the pore-bearing rock mass shows the characteristics of higher ringing count, AE energy, b-value peak, and more cumulative ringing count in the failure stage, while it shows lower characteristics under cyclic action. At the initial stage of loading, compared with the intact rock mass, the pore-containing rock mass shows the characteristics of a low b-value. The AE positioning and cumulative damage percentage are larger, and the AE positioning is denser around the hole. The specimen with holes is mainly shear failure, and the complete specimen is mainly tensile shear failure.
文摘射频四极场(Radio frequency quodrupole,RFQ)加速器是一种非常适于用作MeV级能量离子注入的加速器。它具有束流强、体积小、使用方便、离子源处在地电位,还可同时加速正、负两种离子等优点。本文介绍了RFQ加速器在国际上的发展状况及其基本原理、北京大学研制的1 MeV RFQ加速器的具体结构、性能以及一种新型RFQ-SFRFQ组合加速器的特点。
文摘目的探讨阵发性心房颤动(PAF)患者左心房功能联合B型脑钠肽(BNP)预测环肺静脉射频消融术(CPVA)后复发的意义。方法选取2017年1月至2018年12月在常州市第一人民医院住院的拟行第一次CPVA术的PAF患者201例。CPVA术前测定患者血液BNP水平;实时三维超声心动图(RT-3DE)获取左心房时间-容积曲线;根据术后3个月动态心电图结果,将PAF患者分为窦性心律组和复发组。应用多因素Logistic回归分析影响CPVA术后PAF复发的独立危险因素;对获得的独立危险因素行预测PAF复发的ROC曲线,比较不同指标的效能。结果201例PAF患者完成CPVA术,随访中36例(17.9%)复发,复发组BNP高于窦性心律组(P<0.05)。2组间左心房最大容积指数(LAVImax)、左心房最小容积指数(LAVImin)差异有统计学意义(均P<0.05);2组间膨胀指数(EI)、舒张期射血指数(DEI)、被动射血指数(PEI)、主动射血指数(AEI)差异均有统计学意义(均P<0.05)。多因素Logistic回归分析表明:术前BNP、DEI及PAF病史是PAF复发的独立预测因素(均P<0.05)。ROC曲线显示:DEI及联合指标(DEI+BNP)预测CPVA术后复发的效能均优于LAVImin(AUC:0.881 vs 0.686、0.901 vs 0.686,均P<0.05);联合诊断的特异性优于DEI及BNP(89.7%vs 79.4%、89.7%vs 72.7%,均P<0.05)。结论CPVA术治疗的PAF患者中,左心房存储功能受损及BNP增高均是CPVA术后PAF复发的独立预测因素,两者联合可提高预测复发的特异度。
