The Bayan Har block,one of China's most seismically active regions,has experienced multiple major earthquakes(≥M 7.0)in recent years.It is a key area for investigating the interactions between the Qinghai-Xizang(...The Bayan Har block,one of China's most seismically active regions,has experienced multiple major earthquakes(≥M 7.0)in recent years.It is a key area for investigating the interactions between the Qinghai-Xizang(Qingzang)Plateau and adjacent blocks,plateau uplift,and strong earthquake mechanisms.P-wave velocity and crustal composition provide key constraints on the properties of distinct tectonic units and their evolutionary modification processes.Based on the results of 8 Deep Seismic Sounding(DSS)profiles completed in the Bayan Har block and surrounding areas over the past 20 years,We constructed one-dimensional P-wave velocity models for the crust of Bayan Har block,Qilian fold belt,Qinling fold belt,Alxa block,Ordos block and Sichuan basin.Furthermore,crustal composition models for different tectonic units were established based on these results.The results reveal that the crustal thickness of the Bayan Har block gradually decreases towards the NNE,NE,and SE directions,while the average crustal velocity increases correspondingly.The felsic layer in the crust accounts for more than half of the total crustal thickness.The mafic content within the crust of different tectonic units exhibits notable variations,which may reflect that the Bayan Har block,Qilian fold belt,and Qinling fold belt have experienced more intensive lithospheric evolution processes compared to Ordos basin and Sichuan basin.The seismicity distribution in this region is significantly controlled by crustal velocity and composition heterogeneity across the Bayan Har block and adjacent areas,which demonstrates that earthquakes within and around the Bayan Har block exhibit both high frequency and larger magnitudes.These seismic characteristics primarily result from intense crustal stress accumulation and release during the outward expansion of the Qingzang Plateau.展开更多
为探究中国铜期货市场价格波动的变化规律并以此预测其风险值,以沪铜期货高频价格数据为样本,综合考虑其收益率波动的聚集性、偏峰厚尾性与长记忆性,将广义已实现测度引入偏t分布假设下的Realized GARCH模型与拓展的Realized HAR GARCH...为探究中国铜期货市场价格波动的变化规律并以此预测其风险值,以沪铜期货高频价格数据为样本,综合考虑其收益率波动的聚集性、偏峰厚尾性与长记忆性,将广义已实现测度引入偏t分布假设下的Realized GARCH模型与拓展的Realized HAR GARCH模型中,并通过样本内拟合与样本外滚动预测,结合似然函数、VaR后验测试与损失函数MCS检验法综合比较了采用不同已实现测度的Realized GARCH以及Realized HAR GARCH模型在沪铜期货收益波动率估计和VaR预测上的效果。实证结果显示:对于沪铜期货市场而言,无论是波动率估计还是风险预测,广义已实现测度的引入显著地提升了Realized GARCH与Realized HAR GARCH模型的拟合效果与预测能力,其中基于日内损失RMAD与RES测度下的Realized HAR GARCH模型分别拥有最优的估计与预测表现。展开更多
文章选取上证综指5分钟收盘价序列高频数据,采用ACF拟合、多种损失函数、SPA检验和VaR回测检验对不同误差分布下的包含时变波动、异方差结构和加权已实现极差的Realized HAR GARCH模型进行研究。实证结果表明,新模型相比于以往模型更能...文章选取上证综指5分钟收盘价序列高频数据,采用ACF拟合、多种损失函数、SPA检验和VaR回测检验对不同误差分布下的包含时变波动、异方差结构和加权已实现极差的Realized HAR GARCH模型进行研究。实证结果表明,新模型相比于以往模型更能够捕捉上证综指的波动特征,具有更好的波动率拟合和预测效果,且VaR度量效果更优。研究丰富了时变长记忆高频波动率模型,从时变波动和噪声异方差结构视角为投资者和监管机构进行风险管控提供参考。展开更多
针对现有深度学习技术在建筑工地高空作业人员安全带检测任务中,存在施工环境复杂、距离远导致检测效率低下的问题,提出一种融合边缘特征增强的级联群注意力工地施工安全带检测模型。首先,该模型在主干网络中进行边缘特征增强,有效提升...针对现有深度学习技术在建筑工地高空作业人员安全带检测任务中,存在施工环境复杂、距离远导致检测效率低下的问题,提出一种融合边缘特征增强的级联群注意力工地施工安全带检测模型。首先,该模型在主干网络中进行边缘特征增强,有效提升了网络对复杂场景下模糊目标形态结构和边缘细节的特征提取;其次,设计CSP(cross stage partial)模块,通过融合级联群注意力(cascaded group attention,CGA)机制,减少冗余信息,提高计算效率;最后,引入融合ELA(efficient local attention)注意力的特征金字塔ELA-HSFPN,实现高、中、低不同尺度的跨分辨率特征高效的动态加权融合,提升了检测精度。实验结果表明,改进后的算法与基准模型YOLOv11n相比,其平均精度值mAP提升了8.27百分点,检测效果明显得到提升,并且和其他的主流目标检测算法相比,也有明显改善,验证了新模型的有效性。展开更多
基金supported by the National Key R&D Program of China(No.2023YFC3012002)the National Natural Science Foundation of China(42374073)。
文摘The Bayan Har block,one of China's most seismically active regions,has experienced multiple major earthquakes(≥M 7.0)in recent years.It is a key area for investigating the interactions between the Qinghai-Xizang(Qingzang)Plateau and adjacent blocks,plateau uplift,and strong earthquake mechanisms.P-wave velocity and crustal composition provide key constraints on the properties of distinct tectonic units and their evolutionary modification processes.Based on the results of 8 Deep Seismic Sounding(DSS)profiles completed in the Bayan Har block and surrounding areas over the past 20 years,We constructed one-dimensional P-wave velocity models for the crust of Bayan Har block,Qilian fold belt,Qinling fold belt,Alxa block,Ordos block and Sichuan basin.Furthermore,crustal composition models for different tectonic units were established based on these results.The results reveal that the crustal thickness of the Bayan Har block gradually decreases towards the NNE,NE,and SE directions,while the average crustal velocity increases correspondingly.The felsic layer in the crust accounts for more than half of the total crustal thickness.The mafic content within the crust of different tectonic units exhibits notable variations,which may reflect that the Bayan Har block,Qilian fold belt,and Qinling fold belt have experienced more intensive lithospheric evolution processes compared to Ordos basin and Sichuan basin.The seismicity distribution in this region is significantly controlled by crustal velocity and composition heterogeneity across the Bayan Har block and adjacent areas,which demonstrates that earthquakes within and around the Bayan Har block exhibit both high frequency and larger magnitudes.These seismic characteristics primarily result from intense crustal stress accumulation and release during the outward expansion of the Qingzang Plateau.
文摘为探究中国铜期货市场价格波动的变化规律并以此预测其风险值,以沪铜期货高频价格数据为样本,综合考虑其收益率波动的聚集性、偏峰厚尾性与长记忆性,将广义已实现测度引入偏t分布假设下的Realized GARCH模型与拓展的Realized HAR GARCH模型中,并通过样本内拟合与样本外滚动预测,结合似然函数、VaR后验测试与损失函数MCS检验法综合比较了采用不同已实现测度的Realized GARCH以及Realized HAR GARCH模型在沪铜期货收益波动率估计和VaR预测上的效果。实证结果显示:对于沪铜期货市场而言,无论是波动率估计还是风险预测,广义已实现测度的引入显著地提升了Realized GARCH与Realized HAR GARCH模型的拟合效果与预测能力,其中基于日内损失RMAD与RES测度下的Realized HAR GARCH模型分别拥有最优的估计与预测表现。
文摘文章选取上证综指5分钟收盘价序列高频数据,采用ACF拟合、多种损失函数、SPA检验和VaR回测检验对不同误差分布下的包含时变波动、异方差结构和加权已实现极差的Realized HAR GARCH模型进行研究。实证结果表明,新模型相比于以往模型更能够捕捉上证综指的波动特征,具有更好的波动率拟合和预测效果,且VaR度量效果更优。研究丰富了时变长记忆高频波动率模型,从时变波动和噪声异方差结构视角为投资者和监管机构进行风险管控提供参考。
文摘针对现有深度学习技术在建筑工地高空作业人员安全带检测任务中,存在施工环境复杂、距离远导致检测效率低下的问题,提出一种融合边缘特征增强的级联群注意力工地施工安全带检测模型。首先,该模型在主干网络中进行边缘特征增强,有效提升了网络对复杂场景下模糊目标形态结构和边缘细节的特征提取;其次,设计CSP(cross stage partial)模块,通过融合级联群注意力(cascaded group attention,CGA)机制,减少冗余信息,提高计算效率;最后,引入融合ELA(efficient local attention)注意力的特征金字塔ELA-HSFPN,实现高、中、低不同尺度的跨分辨率特征高效的动态加权融合,提升了检测精度。实验结果表明,改进后的算法与基准模型YOLOv11n相比,其平均精度值mAP提升了8.27百分点,检测效果明显得到提升,并且和其他的主流目标检测算法相比,也有明显改善,验证了新模型的有效性。
