In this paper, we present a simple Stokes parameter measurement method for a rotating quarter-wave plate polarimeter. This method is used to construct a model to describe the principle of how the magnitudes of errors ...In this paper, we present a simple Stokes parameter measurement method for a rotating quarter-wave plate polarimeter. This method is used to construct a model to describe the principle of how the magnitudes of errors influence the deviation of the output light Stokes parameter, on the basis of accuracy analysis of the retardance error of the quarter-wave plate, the misalignment of the analyzing polarizer, and the phase shift of the measured signals, which will help us to determine the magnitudes of these errors and then to acquire the correct results of Stokes parameters. The method is validated by the experiments on left-handed circularly polarized and linear horizontal polarization beams. With the improved method, the maximum measurement deviations of Stokes parameters for these two different polarized states are reduced from 2.72% to 2.68%, and from 3.83% to 1.06% respectively. Our results demonstrate that the proposed method can be used as a promising approach to Stokes parameter measurement for a rotating quarter-wave plate polarimeter.展开更多
Line parameters play an important role in the control and management of distribution systems.Currently,phasor measurement unit(PMU)systems and supervisory control and data acquisition(SCADA)systems coexist in distribu...Line parameters play an important role in the control and management of distribution systems.Currently,phasor measurement unit(PMU)systems and supervisory control and data acquisition(SCADA)systems coexist in distribution systems.Unfortunately,SCADA and PMU measurements usually do not match each other,resulting in inaccurate detection and identification of line parameters based on measurements.To solve this problem,a data-driven method is proposed.SCADA measurements are taken as samples and PMU measurements as the population.A probability parameter identification index(PPII)is derived to detect the whole line parameter based on the probability density function(PDF)parameters of the measurements.For parameter identification,a power-loss PDF with the PMU time stamps and a power-loss chronological PDF are derived via kernel density estimation(KDE)and a conditional PDF.Then,the power-loss samples with the PMU time stamps and chronological correlations are generated by the two PDFs of the power loss via the Metropolis-Hastings(MH)algorithm.Finally,using the power-loss samples and PMU current measurements,the line parameters are identified using the total least squares(TLS)algorithm.Hardware simulations demonstrate the effectiveness of the proposed method for distribution network line parameter detection and identification.展开更多
Detecting multiple parameters in salt spray environments is critical,as it significantly enhances the stability and reliability of real-time corrosion monitoring systems.However,current sensor strategies for detecting...Detecting multiple parameters in salt spray environments is critical,as it significantly enhances the stability and reliability of real-time corrosion monitoring systems.However,current sensor strategies for detecting salt spray parameters face challenges such as poor timeliness,short lifespan,and low detection accuracy.This work introduces a multi-parameter micro-nano sensor based on Micro-Electro-Mechanical Systems(MEMS)technology,which integrates temperature,humidity,and conductivity detection units.Through a systematic characterization of the sensor’s performance,the sensor demonstrates excellent linearity,ideal detection ranges,and satisfactory accuracies with detection accuracies of±0.1℃ for temperature,±2%RH for humidity,and±0.1 mS/cm for conductivity.This sensor offers a practical strategy for calculating the instantaneous corrosion rate of aircraft over the ocean.Additionally,based on the positive correlation between the three parameters and the liquid film thickness,a critical threshold determination method for the dynamic behavior of the sensor surface liquid film is further explored.This method macroscopically distinguishes the phase transition boundary between dry and wet states of the liquid film,offering a theoretical foundation for differentiated corrosion rate assessment and improved corrosion prediction accuracy.Highprecision monitoring of environmental parameters during long-term salt spray and atmospheric exposure experiments is achieved using a self-developed online testing system.Real-time data compensation is also provided to improve the sensor’s stability and accuracy.Consequently,the proposed high-precision,miniaturized,and massproducible multi-parameter sensor holds great promise as a competitive device for detecting salt spray environmental parameters in real-time corrosion monitoring systems for the aerospace field.展开更多
A concise fractional Fourier transform （CFRFT） is proposed to detect the linear frequency-modulated （LFM） signal with low signal to noise ratio （SNR）. The frequency axis in time-frequency plane of the CFRFT is r...A concise fractional Fourier transform （CFRFT） is proposed to detect the linear frequency-modulated （LFM） signal with low signal to noise ratio （SNR）. The frequency axis in time-frequency plane of the CFRFT is rotated to get the spectrum of the signal in different an- gles using chirp multiplication and Fourier transform （FT）. For LFM signal which distributes as a straight line in time-frequency plane, the CFRFT can gather the energy in the corresponding angle as a peak and improve the detection SNR, thus the LFM signal of low SNR can be de- tected. Meanwhile, the location of the peak value relates to the parameters of the LFM signal. Numerical simulations and experimental results show that, the proposed method can be used to efficiently detect the LFM signal masked by noise and to estimate the signal＇s parameters accurately. Compared with the conventional fractional Fourier transform （FRFT）, the CFRFT reduces the transform complexity and improves the real-time detection performance of LFM signal.展开更多
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2015AA123702)the National Natural Science Foundation of China(Grant No.61505222)
文摘In this paper, we present a simple Stokes parameter measurement method for a rotating quarter-wave plate polarimeter. This method is used to construct a model to describe the principle of how the magnitudes of errors influence the deviation of the output light Stokes parameter, on the basis of accuracy analysis of the retardance error of the quarter-wave plate, the misalignment of the analyzing polarizer, and the phase shift of the measured signals, which will help us to determine the magnitudes of these errors and then to acquire the correct results of Stokes parameters. The method is validated by the experiments on left-handed circularly polarized and linear horizontal polarization beams. With the improved method, the maximum measurement deviations of Stokes parameters for these two different polarized states are reduced from 2.72% to 2.68%, and from 3.83% to 1.06% respectively. Our results demonstrate that the proposed method can be used as a promising approach to Stokes parameter measurement for a rotating quarter-wave plate polarimeter.
基金supported by the National Key Research and Development Program under Grant 2017YFB0902900 and Grant 2017YFB0902902。
文摘Line parameters play an important role in the control and management of distribution systems.Currently,phasor measurement unit(PMU)systems and supervisory control and data acquisition(SCADA)systems coexist in distribution systems.Unfortunately,SCADA and PMU measurements usually do not match each other,resulting in inaccurate detection and identification of line parameters based on measurements.To solve this problem,a data-driven method is proposed.SCADA measurements are taken as samples and PMU measurements as the population.A probability parameter identification index(PPII)is derived to detect the whole line parameter based on the probability density function(PDF)parameters of the measurements.For parameter identification,a power-loss PDF with the PMU time stamps and a power-loss chronological PDF are derived via kernel density estimation(KDE)and a conditional PDF.Then,the power-loss samples with the PMU time stamps and chronological correlations are generated by the two PDFs of the power loss via the Metropolis-Hastings(MH)algorithm.Finally,using the power-loss samples and PMU current measurements,the line parameters are identified using the total least squares(TLS)algorithm.Hardware simulations demonstrate the effectiveness of the proposed method for distribution network line parameter detection and identification.
基金supported by the grant from the National Science Foundation of China(62271272)the Open Fund Project of Key Laboratory of Ocean Observation Technology,MNR(2023klootA09)sponsored by Ningbo Science and Technology Project(2022Z092).
文摘Detecting multiple parameters in salt spray environments is critical,as it significantly enhances the stability and reliability of real-time corrosion monitoring systems.However,current sensor strategies for detecting salt spray parameters face challenges such as poor timeliness,short lifespan,and low detection accuracy.This work introduces a multi-parameter micro-nano sensor based on Micro-Electro-Mechanical Systems(MEMS)technology,which integrates temperature,humidity,and conductivity detection units.Through a systematic characterization of the sensor’s performance,the sensor demonstrates excellent linearity,ideal detection ranges,and satisfactory accuracies with detection accuracies of±0.1℃ for temperature,±2%RH for humidity,and±0.1 mS/cm for conductivity.This sensor offers a practical strategy for calculating the instantaneous corrosion rate of aircraft over the ocean.Additionally,based on the positive correlation between the three parameters and the liquid film thickness,a critical threshold determination method for the dynamic behavior of the sensor surface liquid film is further explored.This method macroscopically distinguishes the phase transition boundary between dry and wet states of the liquid film,offering a theoretical foundation for differentiated corrosion rate assessment and improved corrosion prediction accuracy.Highprecision monitoring of environmental parameters during long-term salt spray and atmospheric exposure experiments is achieved using a self-developed online testing system.Real-time data compensation is also provided to improve the sensor’s stability and accuracy.Consequently,the proposed high-precision,miniaturized,and massproducible multi-parameter sensor holds great promise as a competitive device for detecting salt spray environmental parameters in real-time corrosion monitoring systems for the aerospace field.
基金supported by the National Natural Science Foundation of China(11434012)
文摘A concise fractional Fourier transform （CFRFT） is proposed to detect the linear frequency-modulated （LFM） signal with low signal to noise ratio （SNR）. The frequency axis in time-frequency plane of the CFRFT is rotated to get the spectrum of the signal in different an- gles using chirp multiplication and Fourier transform （FT）. For LFM signal which distributes as a straight line in time-frequency plane, the CFRFT can gather the energy in the corresponding angle as a peak and improve the detection SNR, thus the LFM signal of low SNR can be de- tected. Meanwhile, the location of the peak value relates to the parameters of the LFM signal. Numerical simulations and experimental results show that, the proposed method can be used to efficiently detect the LFM signal masked by noise and to estimate the signal＇s parameters accurately. Compared with the conventional fractional Fourier transform （FRFT）, the CFRFT reduces the transform complexity and improves the real-time detection performance of LFM signal.
