Traditional passive flexible protection systems often fail under high-energy rockfall impacts,leading to structural destruction and casualties.To address this critical limitation,this study develops a novel high-ducti...Traditional passive flexible protection systems often fail under high-energy rockfall impacts,leading to structural destruction and casualties.To address this critical limitation,this study develops a novel high-ductility energy-absorbing(HDEA)system incorporating negative Poisson's ratio(NPR)materials.The mechanical performance of the HDEA system was comprehensively evaluated through an integrated methodology comprising static/dynamic tests,finite element simulation,and field monitoring.Quasi-static tensile and drop hammer impact tests were conducted on conventional positive Poisson's ratio(PR)steel and NPR materials.The NPR material exhibits 54.4%-68.8%higher tensile strength and 1.04-1.31 times greater elongation at break than the PR material.Dynamic tests reveal the NPR cable achieves 44.29%lower single-impact deformation with 1.39 times higher cumulative impact deformation versus the PR counterpart.These results indicate that the NPR material breaks the strength-ductility trade-off,equipping the cable with both high impact resistance and exceptional energy absorption.The fastener transits from plastic deformation to fracture under extreme conditions while the NPR cables retain integrity.This contrasting behavior validates a deliberate failure hierarchy,where the fastener acts as a sacrificial component,thereby preserving the integrity and reusability of the NPR cable.Slip resistance tests verify an anti-slip capacity exceeding 350 kN.This confirms a robust interfacial bond between the cable and fastener,which is critical for ensuring the coordinated deformation of the entire interception net under rockfall impact.Field implementation demonstrates the HDEA system withstands daily average of 3 rockfall impacts with 2000 J mean impact energy while maintaining structural integrity.This study pioneers the application of NPR materials in rockfall protection systems,providing a groundbreaking solution for mitigating high-energy rockfall hazards.展开更多
针对矿井TOA(Time of Arrival)定位精度易受电磁波NLOS(Non Line of Sight)传播时延的影响,且不能满足井下应急救援、人员作业管理以及矿井物联网建设等需求的问题,通过对NLOS时延参考模型和矿井巷道设备运动特点的分析,将巷道电磁波NLO...针对矿井TOA(Time of Arrival)定位精度易受电磁波NLOS(Non Line of Sight)传播时延的影响,且不能满足井下应急救援、人员作业管理以及矿井物联网建设等需求的问题,通过对NLOS时延参考模型和矿井巷道设备运动特点的分析,将巷道电磁波NLOS传播时延分为随机NLOS时延和固定NLOS时延,结合两类NLOS时延造成测距误差的特点,提出了基于改进卡尔曼滤波和参数拟合的矿井TOA定位方法。为了消除由矿井巷道中机车等移动设备以及不规律设置设备引起的、具有随机性和难以定量分析等特点的巷道随机NLOS时延误差,设计了将新息阈值引入卡尔曼滤波器中,提高其系统对脉冲误差的滤除能力的方法;为了抑制由矿井巷道中固定设施及设备造成的具有稳定性的巷道固定NLOS时延误差,建立了巷道测距误差模型,构建了井下固有设备参数与定位估计值间的函数关系,通过参数拟合与投影几何算法来提高系统的定位精度。仿真结果显示,测量数据经过基于新息阈值的卡尔曼滤波器处理之后,误差曲线趋于平稳,定位误差保持在1.9~3.1m,再经参数拟合和几何算法处理后,定位误差在0~0.8m,平均误差由2.4m降为0.3m;且相比于SDS-TWR(Symmetric Double-Sided Two-Way Ranging)方法、卡尔曼滤波和指纹定位方法以及卡尔曼滤波和参数拟合方法,所提方法平均定位误差分别减小了3.4,0.4和0.6m。从而表明所提方法对TOA定位误差具有较明显的抑制作用,可以实现TOA方法在矿井NLOS环境中的有效应用。展开更多
为了研究水树老化电缆极化-去极化电流(polarization and depolarization current,PDC)支路参数变化特征及原因,分析了水树微观结构特征,并揭示了水树微观结构对电缆PDC支路参数的影响。对短电缆和长电缆样本进行加速水树老化,利用PDC...为了研究水树老化电缆极化-去极化电流(polarization and depolarization current,PDC)支路参数变化特征及原因,分析了水树微观结构特征,并揭示了水树微观结构对电缆PDC支路参数的影响。对短电缆和长电缆样本进行加速水树老化,利用PDC检测样本极化–去极化电流,并计算老化样本Debye模型三支路参数。利用光学显微镜观测短电缆样本中的水树形态,利用扫描电镜(scanning electron microscopy,SEM)观测水树区域微观形貌。PDC三支路参数辨识结果表明,水树老化样本第3支路时间常数显著高于未老化样本。另外,第3支路电容增加量高于电阻减小量。微观观测结果表明水树区域存在大量孤立微孔,分析认为,水树生长将造成材料分子链断裂及形成大量微孔–XLPE界面,导致材料偶极极化时间及界面极化时间增长,样本第3支路时间常数显著增大。另外,水树区域存在大量孤立微孔,其限制了离子在水树区域的运动,从而导致样本第3支路电容增大量高于电阻减小量。展开更多
基金financial support from the National Natural Science Foundation of China-Railway Fundamental Research Joint Fund Project(U2468219)National Natural Science Foundation of China(Grant No.42377195)。
文摘Traditional passive flexible protection systems often fail under high-energy rockfall impacts,leading to structural destruction and casualties.To address this critical limitation,this study develops a novel high-ductility energy-absorbing(HDEA)system incorporating negative Poisson's ratio(NPR)materials.The mechanical performance of the HDEA system was comprehensively evaluated through an integrated methodology comprising static/dynamic tests,finite element simulation,and field monitoring.Quasi-static tensile and drop hammer impact tests were conducted on conventional positive Poisson's ratio(PR)steel and NPR materials.The NPR material exhibits 54.4%-68.8%higher tensile strength and 1.04-1.31 times greater elongation at break than the PR material.Dynamic tests reveal the NPR cable achieves 44.29%lower single-impact deformation with 1.39 times higher cumulative impact deformation versus the PR counterpart.These results indicate that the NPR material breaks the strength-ductility trade-off,equipping the cable with both high impact resistance and exceptional energy absorption.The fastener transits from plastic deformation to fracture under extreme conditions while the NPR cables retain integrity.This contrasting behavior validates a deliberate failure hierarchy,where the fastener acts as a sacrificial component,thereby preserving the integrity and reusability of the NPR cable.Slip resistance tests verify an anti-slip capacity exceeding 350 kN.This confirms a robust interfacial bond between the cable and fastener,which is critical for ensuring the coordinated deformation of the entire interception net under rockfall impact.Field implementation demonstrates the HDEA system withstands daily average of 3 rockfall impacts with 2000 J mean impact energy while maintaining structural integrity.This study pioneers the application of NPR materials in rockfall protection systems,providing a groundbreaking solution for mitigating high-energy rockfall hazards.
文摘针对矿井TOA(Time of Arrival)定位精度易受电磁波NLOS(Non Line of Sight)传播时延的影响,且不能满足井下应急救援、人员作业管理以及矿井物联网建设等需求的问题,通过对NLOS时延参考模型和矿井巷道设备运动特点的分析,将巷道电磁波NLOS传播时延分为随机NLOS时延和固定NLOS时延,结合两类NLOS时延造成测距误差的特点,提出了基于改进卡尔曼滤波和参数拟合的矿井TOA定位方法。为了消除由矿井巷道中机车等移动设备以及不规律设置设备引起的、具有随机性和难以定量分析等特点的巷道随机NLOS时延误差,设计了将新息阈值引入卡尔曼滤波器中,提高其系统对脉冲误差的滤除能力的方法;为了抑制由矿井巷道中固定设施及设备造成的具有稳定性的巷道固定NLOS时延误差,建立了巷道测距误差模型,构建了井下固有设备参数与定位估计值间的函数关系,通过参数拟合与投影几何算法来提高系统的定位精度。仿真结果显示,测量数据经过基于新息阈值的卡尔曼滤波器处理之后,误差曲线趋于平稳,定位误差保持在1.9~3.1m,再经参数拟合和几何算法处理后,定位误差在0~0.8m,平均误差由2.4m降为0.3m;且相比于SDS-TWR(Symmetric Double-Sided Two-Way Ranging)方法、卡尔曼滤波和指纹定位方法以及卡尔曼滤波和参数拟合方法,所提方法平均定位误差分别减小了3.4,0.4和0.6m。从而表明所提方法对TOA定位误差具有较明显的抑制作用,可以实现TOA方法在矿井NLOS环境中的有效应用。
文摘为了研究水树老化电缆极化-去极化电流(polarization and depolarization current,PDC)支路参数变化特征及原因,分析了水树微观结构特征,并揭示了水树微观结构对电缆PDC支路参数的影响。对短电缆和长电缆样本进行加速水树老化,利用PDC检测样本极化–去极化电流,并计算老化样本Debye模型三支路参数。利用光学显微镜观测短电缆样本中的水树形态,利用扫描电镜(scanning electron microscopy,SEM)观测水树区域微观形貌。PDC三支路参数辨识结果表明,水树老化样本第3支路时间常数显著高于未老化样本。另外,第3支路电容增加量高于电阻减小量。微观观测结果表明水树区域存在大量孤立微孔,分析认为,水树生长将造成材料分子链断裂及形成大量微孔–XLPE界面,导致材料偶极极化时间及界面极化时间增长,样本第3支路时间常数显著增大。另外,水树区域存在大量孤立微孔,其限制了离子在水树区域的运动,从而导致样本第3支路电容增大量高于电阻减小量。
