A regularized recursive linearization method is developed for a two-dimensional in-verse medium scattering problem that arises in near-field optics, which reconstructs the scatterer of an inhomogeneous medium deposite...A regularized recursive linearization method is developed for a two-dimensional in-verse medium scattering problem that arises in near-field optics, which reconstructs the scatterer of an inhomogeneous medium deposited on a homogeneous substrate from data accessible through photon scanning tunneling microscopy experiments. In addition to the ill-posedness of the inverse scattering problems, two difficulties arise from the layered back-ground medium and limited aperture data. Based on multiple frequency scattering data, the method starts from the Born approximation corresponding to the weak scattering at a low frequency, each update is obtained via recursive linearization with respect to the wavenumber by solving one forward problem and one adjoint problem of the Helmholtz equation. Numerical experiments are included to illustrate the feasibility of the proposed method.展开更多
超大规模天线阵列在近期取得了快速发展并有望在未来无线通信,尤其是在中频和毫米波频段取得广泛应用。随着天线孔径的提升,近场效应变得更为明显和突出,因此传统远场平面波假设不再适用。为更准确地对近场通信进行性能评估,建立准确反...超大规模天线阵列在近期取得了快速发展并有望在未来无线通信,尤其是在中频和毫米波频段取得广泛应用。随着天线孔径的提升,近场效应变得更为明显和突出,因此传统远场平面波假设不再适用。为更准确地对近场通信进行性能评估,建立准确反映近场信道特性的信道模型尤为关键,基于电磁理论和物理光学,建立了一般散射体的散射模型。通过对近场散射体散射特性的研究,分析了非视距(Non-Line of Sight,NLoS)径信道状态的变化特点以及近场场景中的空间非平稳(Spatial Non-Stationary,SNS)特征。基于大规模收发天线阵元间空间一致性特性,结合散射体散射特性,设计了基于空间一致性的近场信道参数生成方法,并提出一种衰减因子计算方法,用以表征空间非平稳特性。在3GPP标准信道建模流程基础上,设计了一种适用于近场电磁波传播的信道模型。提出的信道模型同时建模了球面波和空间非平稳特性对近场通信的影响,可准确评估近场通信性能,为近场码本设计、波束成型等技术的发展打下基础。展开更多
Angular glint is a significant electromagnetic （EM） scattering signature of extended radar targets. Based on the adaptive cross approximation （ACA） algorithm accelerated method of moments （MoM） and the plane inc...Angular glint is a significant electromagnetic （EM） scattering signature of extended radar targets. Based on the adaptive cross approximation （ACA） algorithm accelerated method of moments （MoM） and the plane incident wave assumption, the narrowband, wideband and newly developed high-resolution range profile （HRRP） based angular glint calculation formulations are derived and applied to arbitrarily shaped three-dimensional （3D） perfectly electrical y conducting （PEC） objects. In addition, the near-field angular glint is emphasized, which is of great importance for radarseeker applications. Furthermore, with the HRRP based angular glint, an approach to rigorously determine range resolution cel s which own relatively smal er angular glint is provided. Numerical results are presented with new findings to demonstrate the usefulness of the developed formulations.展开更多
We review the recent biomedical detection developments of scanning near-field optical microscopy(SNOM),focusing on scattering-type SNOM,atomic force microscope-based infrared spectroscopy,peak force infrared microscop...We review the recent biomedical detection developments of scanning near-field optical microscopy(SNOM),focusing on scattering-type SNOM,atomic force microscope-based infrared spectroscopy,peak force infrared microscopy,and photo-induced force microscopy,which have the advantages of label-free,noninvasive,and specific spectral recognition.Considering the high water content of biological samples and the strong absorption of water by infrared waves,we divide the relevant research on these techniques into two categories:one based on a nonliquid environment and the other based on a liquid environment.In the nonliquid environment,the chemical composition and structural information of biomedical samples can be obtained with nanometer resolution.In the liquid environment,these techniques can be used to monitor the dynamic chemical reaction process and track the process of chemical composition and structural change of single molecules,which is conducive to exploring the development mechanism of physiological processes.We elaborate their experimental challenges,technical means,and actual cases for three microbiomedical samples(including biomacromolecules,cells,and tissues).We also discuss the prospects and challenges for their development.Our work lays a foundation for the rational design and efficient use of near-field optical microscopy to explore the characteristics of microscopic biology.展开更多
基金The research was supported in part by the ONR grant N000140210365the NSF grants DMS-0604790 and CCF-0514078the National Science Foundation of China grant 10428105.
文摘A regularized recursive linearization method is developed for a two-dimensional in-verse medium scattering problem that arises in near-field optics, which reconstructs the scatterer of an inhomogeneous medium deposited on a homogeneous substrate from data accessible through photon scanning tunneling microscopy experiments. In addition to the ill-posedness of the inverse scattering problems, two difficulties arise from the layered back-ground medium and limited aperture data. Based on multiple frequency scattering data, the method starts from the Born approximation corresponding to the weak scattering at a low frequency, each update is obtained via recursive linearization with respect to the wavenumber by solving one forward problem and one adjoint problem of the Helmholtz equation. Numerical experiments are included to illustrate the feasibility of the proposed method.
文摘超大规模天线阵列在近期取得了快速发展并有望在未来无线通信,尤其是在中频和毫米波频段取得广泛应用。随着天线孔径的提升,近场效应变得更为明显和突出,因此传统远场平面波假设不再适用。为更准确地对近场通信进行性能评估,建立准确反映近场信道特性的信道模型尤为关键,基于电磁理论和物理光学,建立了一般散射体的散射模型。通过对近场散射体散射特性的研究,分析了非视距(Non-Line of Sight,NLoS)径信道状态的变化特点以及近场场景中的空间非平稳(Spatial Non-Stationary,SNS)特征。基于大规模收发天线阵元间空间一致性特性,结合散射体散射特性,设计了基于空间一致性的近场信道参数生成方法,并提出一种衰减因子计算方法,用以表征空间非平稳特性。在3GPP标准信道建模流程基础上,设计了一种适用于近场电磁波传播的信道模型。提出的信道模型同时建模了球面波和空间非平稳特性对近场通信的影响,可准确评估近场通信性能,为近场码本设计、波束成型等技术的发展打下基础。
文摘Angular glint is a significant electromagnetic （EM） scattering signature of extended radar targets. Based on the adaptive cross approximation （ACA） algorithm accelerated method of moments （MoM） and the plane incident wave assumption, the narrowband, wideband and newly developed high-resolution range profile （HRRP） based angular glint calculation formulations are derived and applied to arbitrarily shaped three-dimensional （3D） perfectly electrical y conducting （PEC） objects. In addition, the near-field angular glint is emphasized, which is of great importance for radarseeker applications. Furthermore, with the HRRP based angular glint, an approach to rigorously determine range resolution cel s which own relatively smal er angular glint is provided. Numerical results are presented with new findings to demonstrate the usefulness of the developed formulations.
基金supported by the National Key Research and Development Program(Grant No.2022YFA1404004)the Key Domestic Scientific and Technological Cooperation Projects in Shanghai(Grant No.21015800200).
文摘We review the recent biomedical detection developments of scanning near-field optical microscopy(SNOM),focusing on scattering-type SNOM,atomic force microscope-based infrared spectroscopy,peak force infrared microscopy,and photo-induced force microscopy,which have the advantages of label-free,noninvasive,and specific spectral recognition.Considering the high water content of biological samples and the strong absorption of water by infrared waves,we divide the relevant research on these techniques into two categories:one based on a nonliquid environment and the other based on a liquid environment.In the nonliquid environment,the chemical composition and structural information of biomedical samples can be obtained with nanometer resolution.In the liquid environment,these techniques can be used to monitor the dynamic chemical reaction process and track the process of chemical composition and structural change of single molecules,which is conducive to exploring the development mechanism of physiological processes.We elaborate their experimental challenges,technical means,and actual cases for three microbiomedical samples(including biomacromolecules,cells,and tissues).We also discuss the prospects and challenges for their development.Our work lays a foundation for the rational design and efficient use of near-field optical microscopy to explore the characteristics of microscopic biology.
