To develop better non-destructive detection technology,we developed the Electrical Resistance Tomography(ERT)inverse algorithm research based on the L-BFGS method and implemented the ERT approach to detect the finite-...To develop better non-destructive detection technology,we developed the Electrical Resistance Tomography(ERT)inverse algorithm research based on the L-BFGS method and implemented the ERT approach to detect the finite-volume targets electrical structure in the construction engineering field and other fi elds.Initially,we compared the forward calculation results with Adam's forward calculation results,and,subsequently,we can see that the electric potential has recovered to a certain extent,indicating that the algorithm is eff ective.Next,the 3D inversion adopts the L-BFGS method based on unstructured grids.The L-BFGS inversion is a regularization inversion,which constrains the model space,adopts a new model smoothing strategy,derives the smoothness operator on the unstructured grid in the finite element,and introduces the L2 norm to define the smoothness of the model.The L-BFGS inversion method improves the inversion effect,which is mainly reflected in saving calculation space,accelerating calculation speed,and providing excellent imaging results.Furthermore,we used the MPI parallel algorithm to speed up the calculation.The accuracy of the algorithm is verifi ed by the inversions of several theoretical models.The ERT algorithm is employed to reconstruct the three-dimensional conductivity distribution within the targets object.Several experiments demonstrate that the ERT method can both locate and image steel bar in concrete,and demonstrate that it is possible to estimate the location of cracks or other insulators(e.g.the plastic plates)in concrete.Besides,the algorithm embodies the advantage that a fi nite-volume targets can be observed on any surface.展开更多
随着对于大规模人群聚集活动的监控需求日益凸显,基于Wi-Fi的人群密度监测技术逐渐应用于公共安全管理,但其受限于RSSI(received signal strength indicator)的显著波动性与MAC地址匿名化造成的个体识别困难,特别在高密度场景下,其估计...随着对于大规模人群聚集活动的监控需求日益凸显,基于Wi-Fi的人群密度监测技术逐渐应用于公共安全管理,但其受限于RSSI(received signal strength indicator)的显著波动性与MAC地址匿名化造成的个体识别困难,特别在高密度场景下,其估计精度与稳定性仍难以保障。对此,提出一种抗随机性的Wi-Fi探针数据人群密度估计方法,通过设计一种基于时间窗的累计RSSI计算策略,利用局部建模构建区域密度映射关系,捕捉区域人群的动态变化,实现了复杂环境下稳定人群密度估计。所提方法在米级精度上分别取得了0.9723的整体准确率和0.8974的高密度场景准确率,实验结果表明其性能良好,具备跨场景推广的理论潜力与良好的泛用性。展开更多
Sub-Saharan Africa(SSA)faces significant resilience challenges which stanched from climate change,economic vulnerabilities,and inadequate social safety nets.These predicaments have not only hindered the region develop...Sub-Saharan Africa(SSA)faces significant resilience challenges which stanched from climate change,economic vulnerabilities,and inadequate social safety nets.These predicaments have not only hindered the region development and stability but also undermined its capacity to resist,adapt to,and recover from both short-and long-term crises.Meanwhile,limited research has focused on its inherent resilience and adaptability strengths in confronting these adversities.Based on theoretical and empirical analysis,this study investigated the dynamic changes in regional resilience in SSA prefectures in response to the 2008 financial crisis and Corona Virus Disease 2019(COVID-19)pandemic through the Fisher Information(FI)method and multi-scale geographical weighted regression model(MGWR).The MGWR model was further complimented with the ordinary least squares(OLS)model for a dynamic comparison.We combined data from various sources and constructed a more dynamic resistance and recoverability indexes and at the same time simulated the adaptability and resilience trend of the region with the help of Python and ArcGIS Software.The findings show that:1)majority of the major regions in SSA present different types of resilience patterns such as‘Stable’,‘Smooth W’,and‘Sharp W’.2)Before the crisis,a larger proportion of SSA regions were unstable and fragile,which resulted in low resistance to the crisis.3)Economic resilience in SSA regions exhibited significant spatial agglomeration and mixed spatial characteristics.4)The eastern regions of SSA have some capacity for shock resistance as they demonstrated a robust resistance index while the western bloc showed greater resilience in recovering from the crisis.5)The resistance to COVID-19 was weaker relatively to the 2008 financial crisis.These findings are crucial as they offer a clear rationale for regional planning during crises,particularly when structural policies may appear less urgent or more appropriate relative to short-term demand policies.Thus,structural vulnerabilities directly inhibit the efficacy of timely responses to crises.Consequently,regional planning must integrate both approaches:using demand policies to address immediate shock,while simultaneously deploying targeted operational policies to strengthen the region’s inborn resilience and effective recovery from shocks.展开更多
随着全球数字化进程加速,地面移动通信网络在海洋、航空及偏远地区存在的覆盖盲区问题日益凸显。为解决此问题,深入研究了Wi-Fi语音(voice over Wi-Fi,VoWi-Fi)与卫星融合通信技术。首先,分析了传统IP语音(voice over IP,VoIP)技术、4G...随着全球数字化进程加速,地面移动通信网络在海洋、航空及偏远地区存在的覆盖盲区问题日益凸显。为解决此问题,深入研究了Wi-Fi语音(voice over Wi-Fi,VoWi-Fi)与卫星融合通信技术。首先,分析了传统IP语音(voice over IP,VoIP)技术、4G/5G语音(LTE承载的语音/新空口承载的语音(voice over LTE/voice over new radio,VoLTE/VoNR))技术与卫星技术融合方案的局限性。在此基础上,提出了一种基于第三代合作伙伴计划(3rd Generation Partnership Project,3GPP)S2b接口架构的VoWi-Fi与“天网地网”模式卫星网络深度融合方案,并设计了跨域业务溯源机制,以满足通信安全要求。实验室系统测试及邮轮、航空等典型场景验证结果表明,该方案语音质量良好,基本与VoLTE/VoNR体验相当,单路语音通话卫星回传带宽需求仅约300~400 kbit/s,在实现全球范围语音、视频、短信业务有效覆盖的同时,保证了良好的用户体验与通信安全。为低成本实现全域通信覆盖提供了一种切实可行的技术路径。展开更多
飞机舱内定位技术在导航定位、物资监管及紧急救援等领域具有重要意义。基于Wi-Fi接收信号强度指示(Received Signal Strength Indicator,RSSI)的定位方法因其易获取、低成本的优势,成为舱内定位研究的重要方向。其中,基于RSSI与距离衰...飞机舱内定位技术在导航定位、物资监管及紧急救援等领域具有重要意义。基于Wi-Fi接收信号强度指示(Received Signal Strength Indicator,RSSI)的定位方法因其易获取、低成本的优势,成为舱内定位研究的重要方向。其中,基于RSSI与距离衰减模型的定位方法操作简单、可移植性强,但定位精度仍有提升空间。针对该方法展开研究,提出一种面向几何图形因子的接入点(Access Point,AP)布局优化方法。通过分析测距误差与几何精度因子的传播关系,建立定位误差的优化模型,推导其解析表达式,并利用改进的Rosen梯度投影法在矩形舱内空间中求得不同AP数量下的最优布局。实验结果表明,所提优化方法能有效降低几何图形因子的影响,进而提高定位精度,为舱内定位系统的部署提供理论依据和优化策略。展开更多
基金supported by the National Key R&D Program of China under Grant No.2022YFF0800601the Hebei Province Langfang Outstanding Young Talents Project under grant No.2370201008.
摘要To develop better non-destructive detection technology,we developed the Electrical Resistance Tomography(ERT)inverse algorithm research based on the L-BFGS method and implemented the ERT approach to detect the finite-volume targets electrical structure in the construction engineering field and other fi elds.Initially,we compared the forward calculation results with Adam's forward calculation results,and,subsequently,we can see that the electric potential has recovered to a certain extent,indicating that the algorithm is eff ective.Next,the 3D inversion adopts the L-BFGS method based on unstructured grids.The L-BFGS inversion is a regularization inversion,which constrains the model space,adopts a new model smoothing strategy,derives the smoothness operator on the unstructured grid in the finite element,and introduces the L2 norm to define the smoothness of the model.The L-BFGS inversion method improves the inversion effect,which is mainly reflected in saving calculation space,accelerating calculation speed,and providing excellent imaging results.Furthermore,we used the MPI parallel algorithm to speed up the calculation.The accuracy of the algorithm is verifi ed by the inversions of several theoretical models.The ERT algorithm is employed to reconstruct the three-dimensional conductivity distribution within the targets object.Several experiments demonstrate that the ERT method can both locate and image steel bar in concrete,and demonstrate that it is possible to estimate the location of cracks or other insulators(e.g.the plastic plates)in concrete.Besides,the algorithm embodies the advantage that a fi nite-volume targets can be observed on any surface.
摘要随着对于大规模人群聚集活动的监控需求日益凸显,基于Wi-Fi的人群密度监测技术逐渐应用于公共安全管理,但其受限于RSSI(received signal strength indicator)的显著波动性与MAC地址匿名化造成的个体识别困难,特别在高密度场景下,其估计精度与稳定性仍难以保障。对此,提出一种抗随机性的Wi-Fi探针数据人群密度估计方法,通过设计一种基于时间窗的累计RSSI计算策略,利用局部建模构建区域密度映射关系,捕捉区域人群的动态变化,实现了复杂环境下稳定人群密度估计。所提方法在米级精度上分别取得了0.9723的整体准确率和0.8974的高密度场景准确率,实验结果表明其性能良好,具备跨场景推广的理论潜力与良好的泛用性。
基金Under the auspices of National Natural Science Foundation of China(No.42571232)the Education Department of Jilin Province(No.JJKH20250320BS)。
摘要Sub-Saharan Africa(SSA)faces significant resilience challenges which stanched from climate change,economic vulnerabilities,and inadequate social safety nets.These predicaments have not only hindered the region development and stability but also undermined its capacity to resist,adapt to,and recover from both short-and long-term crises.Meanwhile,limited research has focused on its inherent resilience and adaptability strengths in confronting these adversities.Based on theoretical and empirical analysis,this study investigated the dynamic changes in regional resilience in SSA prefectures in response to the 2008 financial crisis and Corona Virus Disease 2019(COVID-19)pandemic through the Fisher Information(FI)method and multi-scale geographical weighted regression model(MGWR).The MGWR model was further complimented with the ordinary least squares(OLS)model for a dynamic comparison.We combined data from various sources and constructed a more dynamic resistance and recoverability indexes and at the same time simulated the adaptability and resilience trend of the region with the help of Python and ArcGIS Software.The findings show that:1)majority of the major regions in SSA present different types of resilience patterns such as‘Stable’,‘Smooth W’,and‘Sharp W’.2)Before the crisis,a larger proportion of SSA regions were unstable and fragile,which resulted in low resistance to the crisis.3)Economic resilience in SSA regions exhibited significant spatial agglomeration and mixed spatial characteristics.4)The eastern regions of SSA have some capacity for shock resistance as they demonstrated a robust resistance index while the western bloc showed greater resilience in recovering from the crisis.5)The resistance to COVID-19 was weaker relatively to the 2008 financial crisis.These findings are crucial as they offer a clear rationale for regional planning during crises,particularly when structural policies may appear less urgent or more appropriate relative to short-term demand policies.Thus,structural vulnerabilities directly inhibit the efficacy of timely responses to crises.Consequently,regional planning must integrate both approaches:using demand policies to address immediate shock,while simultaneously deploying targeted operational policies to strengthen the region’s inborn resilience and effective recovery from shocks.
摘要随着全球数字化进程加速,地面移动通信网络在海洋、航空及偏远地区存在的覆盖盲区问题日益凸显。为解决此问题,深入研究了Wi-Fi语音(voice over Wi-Fi,VoWi-Fi)与卫星融合通信技术。首先,分析了传统IP语音(voice over IP,VoIP)技术、4G/5G语音(LTE承载的语音/新空口承载的语音(voice over LTE/voice over new radio,VoLTE/VoNR))技术与卫星技术融合方案的局限性。在此基础上,提出了一种基于第三代合作伙伴计划(3rd Generation Partnership Project,3GPP)S2b接口架构的VoWi-Fi与“天网地网”模式卫星网络深度融合方案,并设计了跨域业务溯源机制,以满足通信安全要求。实验室系统测试及邮轮、航空等典型场景验证结果表明,该方案语音质量良好,基本与VoLTE/VoNR体验相当,单路语音通话卫星回传带宽需求仅约300~400 kbit/s,在实现全球范围语音、视频、短信业务有效覆盖的同时,保证了良好的用户体验与通信安全。为低成本实现全域通信覆盖提供了一种切实可行的技术路径。
摘要飞机舱内定位技术在导航定位、物资监管及紧急救援等领域具有重要意义。基于Wi-Fi接收信号强度指示(Received Signal Strength Indicator,RSSI)的定位方法因其易获取、低成本的优势,成为舱内定位研究的重要方向。其中,基于RSSI与距离衰减模型的定位方法操作简单、可移植性强,但定位精度仍有提升空间。针对该方法展开研究,提出一种面向几何图形因子的接入点(Access Point,AP)布局优化方法。通过分析测距误差与几何精度因子的传播关系,建立定位误差的优化模型,推导其解析表达式,并利用改进的Rosen梯度投影法在矩形舱内空间中求得不同AP数量下的最优布局。实验结果表明,所提优化方法能有效降低几何图形因子的影响,进而提高定位精度,为舱内定位系统的部署提供理论依据和优化策略。