针对ISAC(integrated sensing and communication)辅助MIMO-OFDM系统中雷达感知信息存在误差时传统信道估计方法性能恶化、导频开销大、计算复杂度高等问题,提出一种面向感知误差的鲁棒两阶段稀疏信道估计框架。第一阶段设计残差能量加...针对ISAC(integrated sensing and communication)辅助MIMO-OFDM系统中雷达感知信息存在误差时传统信道估计方法性能恶化、导频开销大、计算复杂度高等问题,提出一种面向感知误差的鲁棒两阶段稀疏信道估计框架。第一阶段设计残差能量加权的同步正交匹配追踪算法REW-SOMP(residual energy weighted simultaneous orthogonal matching pursuit),通过局部字典自适应扩展与残差加权路径筛选机制,在感知误差下准确提取通信关联路径;第二阶段提出自适应惩罚因子交替方向乘子算法AP-ADMM(adaptive penalty factor alternating direction method of multipliers),动态平衡原始残差与对偶残差以优化信道增益估计,有效解决固定惩罚因子导致的收敛速度与精度矛盾问题。仿真结果表明:在3GPP标准信道下,导频密度仅为6.25%时,所提方法相较于传统宽带算法不仅可获得更好的NMSE性能,且在感知误差大时仍保持鲁棒性,同时显著降低了计算复杂度。展开更多
[目的]通过文献计量方法识别长江经济带重点湖泊研究热点、发展脉络与前沿趋势,为后续研究及政策制定提供科学参考。[方法]基于中国知网(CNKI)和Web of Science(WOS)核心数据库,检索1979年至今与长江经济带重点湖泊生态环境相关的中英...[目的]通过文献计量方法识别长江经济带重点湖泊研究热点、发展脉络与前沿趋势,为后续研究及政策制定提供科学参考。[方法]基于中国知网(CNKI)和Web of Science(WOS)核心数据库,检索1979年至今与长江经济带重点湖泊生态环境相关的中英文文献,最终纳入中文文献5 081篇、英文文献2 243篇。运用CiteSpace 6.3.R1软件进行关键词共现分析、聚类分析、突现词检测和时间线图谱绘制,从年度发文量、研究热点与演进趋势等方面开展多维可视化分析。[结果](1)年度发文量可分为4个时期:研究初期(1979—1995年,年均发文量<50篇)、缓慢增长期(1996—2003年)、快速增长期(2004—2015年)和国际影响力提升期(2016至今),其中国家政策与重大环境事件(如太湖蓝藻事件)显著影响研究进程;(2)研究热点集中于湖泊富营养化机制与治理、水质与沉积物污染特征及风险评估、气候变化与人类活动对湖泊生态的驱动影响、生态修复与生物多样性保护以及遥感与智能监测技术应用5个方面;(3)研究前沿从早期的局部污染治理逐步转向多维度、系统性研究,突出表现为近年来的强突现词如“气候变化”(2022至今)、“景观格局”(2015至今)和“ecosystem services”(2019—2021),表明对社会-生态系统协同性与江湖一体关系的关注持续增强。[结论]长江经济带湖泊生态环境研究呈现出从问题识别到驱动解析,再到治理响应的完整研究链条,已形成较为鲜明的理论与实践体系。未来需进一步加强多尺度耦合机制、湖泊跨区域生态补偿与用途管制协同优化研究,深化基于自然的解决方案(NbS)在湖泊修复中的应用,以支撑长江经济带生态保护与高质量发展。展开更多
Conductive polymer foam(CPF)with excellent compressibility and variable resistance has promising applications in electromagnetic interference(EMI)shielding and other integrated functions for wearable electronics.Howev...Conductive polymer foam(CPF)with excellent compressibility and variable resistance has promising applications in electromagnetic interference(EMI)shielding and other integrated functions for wearable electronics.However,its insufficient change amplitude of resistance with compressive strain generally leads to a degradation of shielding performance during deformation.Here,an innovative loading strategy of conductive materials on polymer foam is proposed to significantly increase the contact probability and contact area of conductive components under compression.Unique inter-skeleton conductive films are constructed by loading alginate-decorated magnetic liquid metal on the polymethacrylate films hanged between the foam skeleton(denoted as AMLM-PM foam).Traditional point contact between conductive skeletons under compression is upgraded to planar contact between conductive films.Therefore,the resistance change of AMLM-PM reaches four orders of magnitude under compression.Moreover,the inter-skeleton conductive films can improve the mechanical strength of foam,prevent the leakage of liquid metal and increase the scattering area of EM wave.AMLM-PM foam has strain-adaptive EMI shielding performance and shows compression-enhanced shielding effectiveness,solving the problem of traditional CPFs upon compression.The upgrade of resistance response also enables foam to achieve sensitive pressure sensing over a wide pressure range and compression-regulated Joule heating function.展开更多
Electromagnetic interference(EMI)shielding materials with adaptive strain capability have broad applications in wearable electronic devices.However,as an important candidate,compressible conductive foam generally suff...Electromagnetic interference(EMI)shielding materials with adaptive strain capability have broad applications in wearable electronic devices.However,as an important candidate,compressible conductive foam generally suffers from a reduction in EMI shielding performance during compression,which limits its application.Here,a compressible conductive aerogel with a unique conductive compensation effect is designed to solve this problem.CuS microspheres with metal-like conductivity serve as conductive compensation sites,and are chemically embedded in the skeletons of lamellar-structured carboxymethylcellulose(CMC)/MXene aerogel through Cu–S−Ti−C chemical bonds.The incorporation of CuS induces circularly-distributed interfacial polarization to enhance the attenuation of EM waves.More importantly,these CuS microspheres act as interlayer bridges to connect the upper and lower MXene/CMC layers during compression,thereby establishing numerous conductive compensation paths to offset the negative effect of thickness reduction on shielding performance.The optimized CMC/MXene/CuS aerogel shows stable EMI shielding performance during compression,and maintains a high shielding effectiveness of∼32.31 dB with increasing compressive strain.In addition,this composite aerogel exhibits good thermal insulation and sound absorption performances,achieving triple shielding functions against EM waves,heat and sound.展开更多
Dear Editor,SO(3)SO(3)This letter proposes a continuous-time semi-decentralized algorithm to minimize a sum of local cost functions on over a multi-agent network.Inspired by the distributed subgradient method in[1],th...Dear Editor,SO(3)SO(3)This letter proposes a continuous-time semi-decentralized algorithm to minimize a sum of local cost functions on over a multi-agent network.Inspired by the distributed subgradient method in[1],the algorithm combines a consensus protocol on with a local Riemannian gradient term,but the state of each agent evolves on the nonlinear manifold.In absence of global information for each node,a coordinator is introduced in the communication network to ensure that all agents achieve convergence with consensus.Resorting to Lyapunov approaches,it is shown that the proposed algorithm reaches an optimal solution.展开更多
摘要针对ISAC(integrated sensing and communication)辅助MIMO-OFDM系统中雷达感知信息存在误差时传统信道估计方法性能恶化、导频开销大、计算复杂度高等问题,提出一种面向感知误差的鲁棒两阶段稀疏信道估计框架。第一阶段设计残差能量加权的同步正交匹配追踪算法REW-SOMP(residual energy weighted simultaneous orthogonal matching pursuit),通过局部字典自适应扩展与残差加权路径筛选机制,在感知误差下准确提取通信关联路径;第二阶段提出自适应惩罚因子交替方向乘子算法AP-ADMM(adaptive penalty factor alternating direction method of multipliers),动态平衡原始残差与对偶残差以优化信道增益估计,有效解决固定惩罚因子导致的收敛速度与精度矛盾问题。仿真结果表明:在3GPP标准信道下,导频密度仅为6.25%时,所提方法相较于传统宽带算法不仅可获得更好的NMSE性能,且在感知误差大时仍保持鲁棒性,同时显著降低了计算复杂度。
基金supported by National Key Research and Development Program of China(2021YBF3501304)National Natural Science Foundation of China(52222106,52371171,51971008,52121001)Natural Science Foundation of Beijing Municipality(2212033).
摘要Conductive polymer foam(CPF)with excellent compressibility and variable resistance has promising applications in electromagnetic interference(EMI)shielding and other integrated functions for wearable electronics.However,its insufficient change amplitude of resistance with compressive strain generally leads to a degradation of shielding performance during deformation.Here,an innovative loading strategy of conductive materials on polymer foam is proposed to significantly increase the contact probability and contact area of conductive components under compression.Unique inter-skeleton conductive films are constructed by loading alginate-decorated magnetic liquid metal on the polymethacrylate films hanged between the foam skeleton(denoted as AMLM-PM foam).Traditional point contact between conductive skeletons under compression is upgraded to planar contact between conductive films.Therefore,the resistance change of AMLM-PM reaches four orders of magnitude under compression.Moreover,the inter-skeleton conductive films can improve the mechanical strength of foam,prevent the leakage of liquid metal and increase the scattering area of EM wave.AMLM-PM foam has strain-adaptive EMI shielding performance and shows compression-enhanced shielding effectiveness,solving the problem of traditional CPFs upon compression.The upgrade of resistance response also enables foam to achieve sensitive pressure sensing over a wide pressure range and compression-regulated Joule heating function.
基金financially supported by the National Key Research and Development Program of China(No.2021YBF3501304)the National Natural Science Foundation of China(Nos.52371171,52222106,51971008,52121001)+1 种基金the Natural Science Foundation of Beijing Municipality(No.2212033)We thank the researchers at the Analysis&Testing Center of Beihang University for their assistance with testing.
摘要Electromagnetic interference(EMI)shielding materials with adaptive strain capability have broad applications in wearable electronic devices.However,as an important candidate,compressible conductive foam generally suffers from a reduction in EMI shielding performance during compression,which limits its application.Here,a compressible conductive aerogel with a unique conductive compensation effect is designed to solve this problem.CuS microspheres with metal-like conductivity serve as conductive compensation sites,and are chemically embedded in the skeletons of lamellar-structured carboxymethylcellulose(CMC)/MXene aerogel through Cu–S−Ti−C chemical bonds.The incorporation of CuS induces circularly-distributed interfacial polarization to enhance the attenuation of EM waves.More importantly,these CuS microspheres act as interlayer bridges to connect the upper and lower MXene/CMC layers during compression,thereby establishing numerous conductive compensation paths to offset the negative effect of thickness reduction on shielding performance.The optimized CMC/MXene/CuS aerogel shows stable EMI shielding performance during compression,and maintains a high shielding effectiveness of∼32.31 dB with increasing compressive strain.In addition,this composite aerogel exhibits good thermal insulation and sound absorption performances,achieving triple shielding functions against EM waves,heat and sound.
基金supported by the National Key Research and Development Program of China(2022YFA1004701)the National Natural Science Foundation of China(72271187,62373283)Shanghai Municipal Science and Technology Major(2021SHZDZX0100).
摘要Dear Editor,SO(3)SO(3)This letter proposes a continuous-time semi-decentralized algorithm to minimize a sum of local cost functions on over a multi-agent network.Inspired by the distributed subgradient method in[1],the algorithm combines a consensus protocol on with a local Riemannian gradient term,but the state of each agent evolves on the nonlinear manifold.In absence of global information for each node,a coordinator is introduced in the communication network to ensure that all agents achieve convergence with consensus.Resorting to Lyapunov approaches,it is shown that the proposed algorithm reaches an optimal solution.