To address the problem of the weak anti-noise and macro-trend extraction abilities of the current methods for identifying radar antenna scan type,a recognition method for radar antenna scan types based on limited pene...To address the problem of the weak anti-noise and macro-trend extraction abilities of the current methods for identifying radar antenna scan type,a recognition method for radar antenna scan types based on limited penetrable visibility graph(LPVG)is proposed.Firstly,seven types of radar antenna scans are analyzed,which include the circular scan,sector scan,helical scan,raster scan,conical scan,electromechanical hybrid scan and two-dimensional electronic scan.Then,the time series of the pulse amplitude in the radar reconnaissance receiver is converted into an LPVG network,and the feature parameters are extracted.Finally,the recognition result is obtained by using a support vector machine(SVM)classifier.The experimental results show that the recognition accuracy and noise resistance of this new method are improved,where the average recognition accuracy for radar antenna type is at least 90%when the signalto-noise ratio(SNR)is 5 dB and above.展开更多
Near-field imaging provides insight into the fundamental light-matter interactions on a nanometer scale.Scattering-type scanning near-field optical microscopy(s-SNOM)is a powerful technique capable of overcoming the d...Near-field imaging provides insight into the fundamental light-matter interactions on a nanometer scale.Scattering-type scanning near-field optical microscopy(s-SNOM)is a powerful technique capable of overcoming the diffraction limit and achieving spatial resolutions below 10 nm(sub-10 nm).However,constrained by the working mechanisms,the signal-to-noise ratio of the imaging is highly affected by undesired background scattering light,which is found to be associated with the optical mode and excitation wavelength,especially for samples with a large specific surface area.Here,we propose a high-resolution method with high-order near-field modes at the infrared range to measure low-dimensional materials.With this technique,we reveal the excitation and propagation of the surface plasmon polaritons in graphene and carbon nanotubes,which was impossible with the low-order imaging approach.Besides,the imaging quality for gold nanoparticles on gold thin film is much better than the AFM results.This paper offers an advanced approach for high-resolution measurement of low-dimensional materials with s-SNOM,owning great potential for sensitive nanoscale imaging.展开更多
1 Mechanism of s-SNOM The concept of utilizing a near-field technique to circumvent the diffraction limit dates back to the early 20th century,proposed by Edward Synge[1].After the first demonstration of this idea,in ...1 Mechanism of s-SNOM The concept of utilizing a near-field technique to circumvent the diffraction limit dates back to the early 20th century,proposed by Edward Synge[1].After the first demonstration of this idea,in 1972 in microwaves[2]and 1984 in visible light[3,4],various practices with similar near-field approaches emerged.Hillenbrand et al.[5]recently reviewed scattering-type scanning near-field optical microscopy(s-SNOM)as a specific type of near-field scanning technique.The detection limit of this near-field scanning technique is characterized by the sharpness of the metallic tip,rather than the wavelength of the electromagnetic wave.Thus,the potential to scan with a very broad frequency range while maintaining an extremely high spatial resolution(nominally 10-100 nm)makes this proposal extremely promising.By analyzing the local dielectric constantϵ(x)as a function of scanning frequency and controlling other environmental parameters,a wealth of physical information can be extracted.展开更多
基金supported by the China Postdoctoral Science Foundation(2015M572694,2016T90979).
文摘To address the problem of the weak anti-noise and macro-trend extraction abilities of the current methods for identifying radar antenna scan type,a recognition method for radar antenna scan types based on limited penetrable visibility graph(LPVG)is proposed.Firstly,seven types of radar antenna scans are analyzed,which include the circular scan,sector scan,helical scan,raster scan,conical scan,electromechanical hybrid scan and two-dimensional electronic scan.Then,the time series of the pulse amplitude in the radar reconnaissance receiver is converted into an LPVG network,and the feature parameters are extracted.Finally,the recognition result is obtained by using a support vector machine(SVM)classifier.The experimental results show that the recognition accuracy and noise resistance of this new method are improved,where the average recognition accuracy for radar antenna type is at least 90%when the signalto-noise ratio(SNR)is 5 dB and above.
基金supported by the China National Funds for Distinguished Young Scientists(No.52225507)the Key Research and Development Program of Shaanxi Province(2024PT-ZCK-40)+1 种基金National Natural Science Foundation of China(52305584)the Fundamental Research Funds for the Central Universities.
文摘Near-field imaging provides insight into the fundamental light-matter interactions on a nanometer scale.Scattering-type scanning near-field optical microscopy(s-SNOM)is a powerful technique capable of overcoming the diffraction limit and achieving spatial resolutions below 10 nm(sub-10 nm).However,constrained by the working mechanisms,the signal-to-noise ratio of the imaging is highly affected by undesired background scattering light,which is found to be associated with the optical mode and excitation wavelength,especially for samples with a large specific surface area.Here,we propose a high-resolution method with high-order near-field modes at the infrared range to measure low-dimensional materials.With this technique,we reveal the excitation and propagation of the surface plasmon polaritons in graphene and carbon nanotubes,which was impossible with the low-order imaging approach.Besides,the imaging quality for gold nanoparticles on gold thin film is much better than the AFM results.This paper offers an advanced approach for high-resolution measurement of low-dimensional materials with s-SNOM,owning great potential for sensitive nanoscale imaging.
文摘1 Mechanism of s-SNOM The concept of utilizing a near-field technique to circumvent the diffraction limit dates back to the early 20th century,proposed by Edward Synge[1].After the first demonstration of this idea,in 1972 in microwaves[2]and 1984 in visible light[3,4],various practices with similar near-field approaches emerged.Hillenbrand et al.[5]recently reviewed scattering-type scanning near-field optical microscopy(s-SNOM)as a specific type of near-field scanning technique.The detection limit of this near-field scanning technique is characterized by the sharpness of the metallic tip,rather than the wavelength of the electromagnetic wave.Thus,the potential to scan with a very broad frequency range while maintaining an extremely high spatial resolution(nominally 10-100 nm)makes this proposal extremely promising.By analyzing the local dielectric constantϵ(x)as a function of scanning frequency and controlling other environmental parameters,a wealth of physical information can be extracted.
