目的无人机摄像资料的分辨率直接影响目标识别与信息获取,所以摄像分辨率的提高具有重大意义。为了改善无人机侦察视频质量,针对目前无人机摄像、照相数据的特点,提出一种无人机侦察视频超分辨率重建方法。方法首先提出基于AGAST-Differ...目的无人机摄像资料的分辨率直接影响目标识别与信息获取,所以摄像分辨率的提高具有重大意义。为了改善无人机侦察视频质量,针对目前无人机摄像、照相数据的特点,提出一种无人机侦察视频超分辨率重建方法。方法首先提出基于AGAST-Difference与Fast Retina Keypoint(FREAK)的特征匹配算法对视频目标帧与相邻帧之间配准,然后提出匹配区域搜索方法找到目标帧与航片的对应关系,利用航片对视频帧进行高频补偿,最后采用凸集投影方法对补偿后视频帧进行迭代优化。结果基于AGAST-Difference与FREAK的特征匹配算法在尺度、旋转、视点等变化及运行速度上存在很大优势,匹配区域搜索方法使无人机视频的高频补偿连续性更好,凸集投影迭代优化提高了重建的边缘保持能力,与一种简单有效的视频序列超分辨率复原算法相比,本文算法重建质量提高约4 d B,运行速度提高约5倍。结论提出了一种针对无人机的视频超分辨率重建方法,分析了无人机视频超分辨率问题的核心所在,并且提出基于AGAST-Difference与FREAK的特征匹配算法与匹配区域搜索方法来解决图像配准与高频补偿问题。实验结果表明,本文算法强化了重建图像的一致性与保真度,特别是对图像边缘细节部分等效果极为明显,且处理速度更快。展开更多
Accurate frequency estimation in a wideband digital receiver using the FFT algorithm encounters challenges, such as spectral leakage resulting from the FFT’s assumption of signal periodicity. High-resolution FFTs pos...Accurate frequency estimation in a wideband digital receiver using the FFT algorithm encounters challenges, such as spectral leakage resulting from the FFT’s assumption of signal periodicity. High-resolution FFTs pose computational demands, and estimating non-integer multiples of frequency resolution proves exceptionally challenging. This paper introduces two novel methods for enhanced frequency precision: polynomial interpolation and array indexing, comparing their results with super-resolution and scalloping loss. Simulation results demonstrate the effectiveness of the proposed methods in contemporary radar systems, with array indexing providing the best frequency estimation despite utilizing maximum hardware resources. The paper demonstrates a trade-off between accurate frequency estimation and hardware resources when comparing polynomial interpolation and array indexing.展开更多
An improved method based on the Tikhonov regularization principle and the precisely known reference station coordinate is proposed to design the regularized matrix. The ill-conditioning of the normal matrix can be imp...An improved method based on the Tikhonov regularization principle and the precisely known reference station coordinate is proposed to design the regularized matrix. The ill-conditioning of the normal matrix can be improved by the regularized matrix. The relative floating ambiguity can be computed only by using the data of several epochs. Combined with the LAMBDA method, the new approach can correctly and quickly fix the integer ambiguity and the success rate is 100% in experiments. Through using measured data sets from four mediumlong baselines, the new method can obtain exact ambiguities only by the Ll-frequency data of three epochs. Compared with the existing methods, the improved method can solve the ambiguities of the medium-long baseline GPS network RTK only using L1-frequency GPS data.展开更多
For a scintillating-fiber array fast-neutron radiography system,a point-spread-function computing model was introduced,and the simulation code was developed. The results of calculation show that fast-neutron radiograp...For a scintillating-fiber array fast-neutron radiography system,a point-spread-function computing model was introduced,and the simulation code was developed. The results of calculation show that fast-neutron radiographs vary with the size of fast neutron sources,the size of fiber cross-section and the imaging geometry. The results suggest that the following qualifications are helpful for a good point spread function: The cross-section of scintillating fibers not greater than 200 μm×200 μm,the size of neutron source as small as a few millimeters,the distance between the source and the scintillating fiber array greater than 1 m,and inspected samples placed as close as possible to the array. The results give suggestions not only to experiment considerations but also to the estimation of spatial resolution for a specific system.展开更多
Fixed-point fast sweeping WENO methods are a class of efficient high-order numerical methods to solve steady-state solutions of hyperbolic partial differential equations(PDEs).The Gauss-Seidel iterations and alternati...Fixed-point fast sweeping WENO methods are a class of efficient high-order numerical methods to solve steady-state solutions of hyperbolic partial differential equations(PDEs).The Gauss-Seidel iterations and alternating sweeping strategy are used to cover characteristics of hyperbolic PDEs in each sweeping order to achieve fast convergence rate to steady-state solutions.A nice property of fixed-point fast sweeping WENO methods which distinguishes them from other fast sweeping methods is that they are explicit and do not require inverse operation of nonlinear local systems.Hence,they are easy to be applied to a general hyperbolic system.To deal with the difficulties associated with numerical boundary treatment when high-order finite difference methods on a Cartesian mesh are used to solve hyperbolic PDEs on complex domains,inverse Lax-Wendroff(ILW)procedures were developed as a very effective approach in the literature.In this paper,we combine a fifthorder fixed-point fast sweeping WENO method with an ILW procedure to solve steadystate solution of hyperbolic conservation laws on complex computing regions.Numerical experiments are performed to test the method in solving various problems including the cases with the physical boundary not aligned with the grids.Numerical results show highorder accuracy and good performance of the method.Furthermore,the method is compared with the popular third-order total variation diminishing Runge-Kutta(TVD-RK3)time-marching method for steady-state computations.Numerical examples show that for most of examples,the fixed-point fast sweeping method saves more than half CPU time costs than TVD-RK3 to converge to steady-state solutions.展开更多
Purpose At present,the high-energy photon source(HEPS)is under construction in Beijing.HEPS has beam emittance lower than 40 pm rad.In order to ensure low beam emittance,a high-performance fast orbit feedback system(F...Purpose At present,the high-energy photon source(HEPS)is under construction in Beijing.HEPS has beam emittance lower than 40 pm rad.In order to ensure low beam emittance,a high-performance fast orbit feedback system(FOFB)is designed for fast and accurate correction of beam orbit.The FOFB needs to have the smallest adjustment step.Therefore,as the execution unit of the FOFB system,the output current resolution of the fast corrector power supply needs to be as small as possible.In FOFB systems,precise correction of beam orbit is required for fast corrector power supply with output current resolution better than 60μA.A precision digital sampling system needs to be designed to meet the high requirements of output current resolution.Method The precision operational amplifier is used to complete the scaling and sampling of signals.The precision operational amplifier is used as the front-end processing in the circuit design to complete the amplitude processing and filtering.Meanwhile,the precision operational amplifier is used as the driver of the precision analog to digital converter(ADC)chip.A precision ADC chips based on oversampling technology is used.With this scheme,the selected ADC chip can have the advantages of both high speed and high precision.A simulation prototype is built for test,and the performance parameters of key chips in the design are given.Results A precision voltage reference is used to test the designed digital sampling system.The test results showed that the acquisition system has an effective resolution of 21.6 bits.The HEPS fast corrector power supply is used for testing the developed precision sampling system.The test result showed that the output current resolution of fast corrector power supply is lower than 16μA.展开更多
China’s Fengyun-3D meteorological satellite launched in December 2016 carries the high-resolution greenhouse-gases absorption spectrometer(GAS)aimed at providing global observations of carbon dioxide(CO_(2)).To date,...China’s Fengyun-3D meteorological satellite launched in December 2016 carries the high-resolution greenhouse-gases absorption spectrometer(GAS)aimed at providing global observations of carbon dioxide(CO_(2)).To date,GAS is one of the few instruments measuring CO_(2) from the near-infrared spectrum.On orbit,the oxygen(O_(2))A band suffers a disturbance,and the signal-to-noise ratio(SNR)is significantly lower than the nominal specification.This leads to difficulties in the retrieval of surface pressure and hence a degradation of the retrieval of the column-averaged CO_(2) dry air mole fraction(XCO_(2))if a full physics retrieval algorithm is used.Thus,a fast CO_(2) inverse method,named semi-physical statistical algorithm,was developed to overcome this deficiency.The instrument characteristics,the semi-physical statistical algorithm,and the results of comparison with ground-based measurements over land were introduced in this paper.XCO_(2) can be obtained from three bands,namely,the O_(2) A,weak CO_(2),and strong CO_(2) bands,with compensation from the Medium Resolution Spectral Imager-2(MERSI-2)products,ECMWF Reanaly-sis v5(ERA-5)data,and Total Carbon Column Observing Network(TCCON)data.The eigenvectors of covariance matrices and the least square fits were used to derive retrieval coefficients and yield cloud-free solutions.In addition to the GAS radiance,some key factors necessary for the accurate estimations of XCO_(2) were also taken as input information(e.g.,air mass,surface pressure,and a priori XCO_(2)).The global GAS XCO_(2) restricted over land was compared against the simultaneously collocated observations from TCCON.The retrieval algorithm can mitigate the issue caused by the low SNR of the O_(2) A band to a certain extent.Overall,through site-by-site comparisons,GAS XCO_(2) agreed well with the average precision(1σ)of 1.52 ppm and bias of−0.007 ppm.The seasonal variation trends of GAS XCO_(2) can be clearly seen at TCCON sites on the 1-yr timescale.展开更多
In this work, we extensively describe and demonstrate the structured dark-field imaging(SDFI). SDFI is a newly proposed x-ray microscopy designed for revealing the fine features below Rayleigh resolution, in which dif...In this work, we extensively describe and demonstrate the structured dark-field imaging(SDFI). SDFI is a newly proposed x-ray microscopy designed for revealing the fine features below Rayleigh resolution, in which different orders of scattered x-ray photons are collected by changing the numerical aperture of the condenser. Here, the samples of single particles are discussed to extend the scope of the SDFI technique reported in a previous work(Chen J, Gao K, Ge X, et al.2013 Opt. Lett. 38 2068). In addition, the details of the newly invented algorithm are explained, which is able to calculate the intensity of any pixel on the image plane rapidly and reliably.展开更多
Three chiral compounds were successfully separated in a short time with two enantiomer separation models on packed-capillary electrochromatography ( CEC ) . (i) 75 μm I.D. capillaries were packed with 5 μm β-cyclod...Three chiral compounds were successfully separated in a short time with two enantiomer separation models on packed-capillary electrochromatography ( CEC ) . (i) 75 μm I.D. capillaries were packed with 5 μm β-cyclodextrin (β-CD) chiral stationary phase (CSP) . Effects of voltage, pH and concentration of organic modifier on electroosmotic flow (EOF) and chiral separations were investigated systematically. Enantiomers of a neutral compound (benzoin) and a neutral drug (mephenytoin) were separated within a short time with high efficiency. Efficiency of 32 000 theoretical plates per meter and resolution (R) of 1.42 were achieved for enantiomers of benzoin using a βCD packed column with 6.2 cm packed length. Efficiency of 45 000 theoretical plates per meter and R of 3 .40 were obtained for enantiomers of mephenytoin. Especially, the enantiomer separation of mephenytion was performed in just 3.4 min with R, of 2.60. (ii) 75 μm I.D. capillary was packed with octadecylsilica particles (ODS) . Chiral separation of a basic drug, propra-nolol, was studied with chiral agent, via addition of the dimethyl-β-cyclodextrin (DM β-CD ) directly into the mobile phase on this column. Baseline separation and efficiency of 81 000 theoretical plates per meter were achieved for propra-nolol.展开更多
High-resolution of Inverse Synthetic Aperture Radar (ISAR) in the azimuth direction can be achieved by increasing the coherent accumulation angle of the target rotation.However, in practice, the coherent accumulation ...High-resolution of Inverse Synthetic Aperture Radar (ISAR) in the azimuth direction can be achieved by increasing the coherent accumulation angle of the target rotation.However, in practice, the coherent accumulation angle may be small.In this paper, a novel algorithm for high-resolution ISAR imaging based on the SParse Iterative Covariance-based Estimation (SPICE) is proposed.As a nonparametric sparse spectrum estimation algorithm, the SPICE algorithm does not need to set any parameters and it converges globally, so it can realize high quality imaging with limited measurements.In addition, a fast implementation of the SPICE algorithm based on the Gohberg-Semencul (G-S) factorization is introduced in this paper.The ISAR imaging of simulated and measured data was analyzed to illustrate the effectiveness of the novel approach.展开更多
文摘目的无人机摄像资料的分辨率直接影响目标识别与信息获取,所以摄像分辨率的提高具有重大意义。为了改善无人机侦察视频质量,针对目前无人机摄像、照相数据的特点,提出一种无人机侦察视频超分辨率重建方法。方法首先提出基于AGAST-Difference与Fast Retina Keypoint(FREAK)的特征匹配算法对视频目标帧与相邻帧之间配准,然后提出匹配区域搜索方法找到目标帧与航片的对应关系,利用航片对视频帧进行高频补偿,最后采用凸集投影方法对补偿后视频帧进行迭代优化。结果基于AGAST-Difference与FREAK的特征匹配算法在尺度、旋转、视点等变化及运行速度上存在很大优势,匹配区域搜索方法使无人机视频的高频补偿连续性更好,凸集投影迭代优化提高了重建的边缘保持能力,与一种简单有效的视频序列超分辨率复原算法相比,本文算法重建质量提高约4 d B,运行速度提高约5倍。结论提出了一种针对无人机的视频超分辨率重建方法,分析了无人机视频超分辨率问题的核心所在,并且提出基于AGAST-Difference与FREAK的特征匹配算法与匹配区域搜索方法来解决图像配准与高频补偿问题。实验结果表明,本文算法强化了重建图像的一致性与保真度,特别是对图像边缘细节部分等效果极为明显,且处理速度更快。
文摘Accurate frequency estimation in a wideband digital receiver using the FFT algorithm encounters challenges, such as spectral leakage resulting from the FFT’s assumption of signal periodicity. High-resolution FFTs pose computational demands, and estimating non-integer multiples of frequency resolution proves exceptionally challenging. This paper introduces two novel methods for enhanced frequency precision: polynomial interpolation and array indexing, comparing their results with super-resolution and scalloping loss. Simulation results demonstrate the effectiveness of the proposed methods in contemporary radar systems, with array indexing providing the best frequency estimation despite utilizing maximum hardware resources. The paper demonstrates a trade-off between accurate frequency estimation and hardware resources when comparing polynomial interpolation and array indexing.
文摘An improved method based on the Tikhonov regularization principle and the precisely known reference station coordinate is proposed to design the regularized matrix. The ill-conditioning of the normal matrix can be improved by the regularized matrix. The relative floating ambiguity can be computed only by using the data of several epochs. Combined with the LAMBDA method, the new approach can correctly and quickly fix the integer ambiguity and the success rate is 100% in experiments. Through using measured data sets from four mediumlong baselines, the new method can obtain exact ambiguities only by the Ll-frequency data of three epochs. Compared with the existing methods, the improved method can solve the ambiguities of the medium-long baseline GPS network RTK only using L1-frequency GPS data.
基金Supported by the Foundation of Double-Hundred Talents of China Academy of Engineering Physics (Grant No. 2004R0301)
文摘For a scintillating-fiber array fast-neutron radiography system,a point-spread-function computing model was introduced,and the simulation code was developed. The results of calculation show that fast-neutron radiographs vary with the size of fast neutron sources,the size of fiber cross-section and the imaging geometry. The results suggest that the following qualifications are helpful for a good point spread function: The cross-section of scintillating fibers not greater than 200 μm×200 μm,the size of neutron source as small as a few millimeters,the distance between the source and the scintillating fiber array greater than 1 m,and inspected samples placed as close as possible to the array. The results give suggestions not only to experiment considerations but also to the estimation of spatial resolution for a specific system.
基金Research was supported by the NSFC Grant 11872210Research was supported by the NSFC Grant 11872210 and Grant No.MCMS-I-0120G01+1 种基金Research supported in part by the AFOSR Grant FA9550-20-1-0055NSF Grant DMS-2010107.
文摘Fixed-point fast sweeping WENO methods are a class of efficient high-order numerical methods to solve steady-state solutions of hyperbolic partial differential equations(PDEs).The Gauss-Seidel iterations and alternating sweeping strategy are used to cover characteristics of hyperbolic PDEs in each sweeping order to achieve fast convergence rate to steady-state solutions.A nice property of fixed-point fast sweeping WENO methods which distinguishes them from other fast sweeping methods is that they are explicit and do not require inverse operation of nonlinear local systems.Hence,they are easy to be applied to a general hyperbolic system.To deal with the difficulties associated with numerical boundary treatment when high-order finite difference methods on a Cartesian mesh are used to solve hyperbolic PDEs on complex domains,inverse Lax-Wendroff(ILW)procedures were developed as a very effective approach in the literature.In this paper,we combine a fifthorder fixed-point fast sweeping WENO method with an ILW procedure to solve steadystate solution of hyperbolic conservation laws on complex computing regions.Numerical experiments are performed to test the method in solving various problems including the cases with the physical boundary not aligned with the grids.Numerical results show highorder accuracy and good performance of the method.Furthermore,the method is compared with the popular third-order total variation diminishing Runge-Kutta(TVD-RK3)time-marching method for steady-state computations.Numerical examples show that for most of examples,the fixed-point fast sweeping method saves more than half CPU time costs than TVD-RK3 to converge to steady-state solutions.
文摘Purpose At present,the high-energy photon source(HEPS)is under construction in Beijing.HEPS has beam emittance lower than 40 pm rad.In order to ensure low beam emittance,a high-performance fast orbit feedback system(FOFB)is designed for fast and accurate correction of beam orbit.The FOFB needs to have the smallest adjustment step.Therefore,as the execution unit of the FOFB system,the output current resolution of the fast corrector power supply needs to be as small as possible.In FOFB systems,precise correction of beam orbit is required for fast corrector power supply with output current resolution better than 60μA.A precision digital sampling system needs to be designed to meet the high requirements of output current resolution.Method The precision operational amplifier is used to complete the scaling and sampling of signals.The precision operational amplifier is used as the front-end processing in the circuit design to complete the amplitude processing and filtering.Meanwhile,the precision operational amplifier is used as the driver of the precision analog to digital converter(ADC)chip.A precision ADC chips based on oversampling technology is used.With this scheme,the selected ADC chip can have the advantages of both high speed and high precision.A simulation prototype is built for test,and the performance parameters of key chips in the design are given.Results A precision voltage reference is used to test the designed digital sampling system.The test results showed that the acquisition system has an effective resolution of 21.6 bits.The HEPS fast corrector power supply is used for testing the developed precision sampling system.The test result showed that the output current resolution of fast corrector power supply is lower than 16μA.
基金Supported by the Civil Aerospace Technology Pre Research Project(D040301)。
文摘China’s Fengyun-3D meteorological satellite launched in December 2016 carries the high-resolution greenhouse-gases absorption spectrometer(GAS)aimed at providing global observations of carbon dioxide(CO_(2)).To date,GAS is one of the few instruments measuring CO_(2) from the near-infrared spectrum.On orbit,the oxygen(O_(2))A band suffers a disturbance,and the signal-to-noise ratio(SNR)is significantly lower than the nominal specification.This leads to difficulties in the retrieval of surface pressure and hence a degradation of the retrieval of the column-averaged CO_(2) dry air mole fraction(XCO_(2))if a full physics retrieval algorithm is used.Thus,a fast CO_(2) inverse method,named semi-physical statistical algorithm,was developed to overcome this deficiency.The instrument characteristics,the semi-physical statistical algorithm,and the results of comparison with ground-based measurements over land were introduced in this paper.XCO_(2) can be obtained from three bands,namely,the O_(2) A,weak CO_(2),and strong CO_(2) bands,with compensation from the Medium Resolution Spectral Imager-2(MERSI-2)products,ECMWF Reanaly-sis v5(ERA-5)data,and Total Carbon Column Observing Network(TCCON)data.The eigenvectors of covariance matrices and the least square fits were used to derive retrieval coefficients and yield cloud-free solutions.In addition to the GAS radiance,some key factors necessary for the accurate estimations of XCO_(2) were also taken as input information(e.g.,air mass,surface pressure,and a priori XCO_(2)).The global GAS XCO_(2) restricted over land was compared against the simultaneously collocated observations from TCCON.The retrieval algorithm can mitigate the issue caused by the low SNR of the O_(2) A band to a certain extent.Overall,through site-by-site comparisons,GAS XCO_(2) agreed well with the average precision(1σ)of 1.52 ppm and bias of−0.007 ppm.The seasonal variation trends of GAS XCO_(2) can be clearly seen at TCCON sites on the 1-yr timescale.
基金supported by the National Basic Research Program of China(Grant No.2012CB825800)the Science Fund for Creative Research Groups,the National Natural Science Foundation of China(Grant Nos.11475170,11205157,11305173,and 11321503)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KJCX2-YW-N42)
文摘In this work, we extensively describe and demonstrate the structured dark-field imaging(SDFI). SDFI is a newly proposed x-ray microscopy designed for revealing the fine features below Rayleigh resolution, in which different orders of scattered x-ray photons are collected by changing the numerical aperture of the condenser. Here, the samples of single particles are discussed to extend the scope of the SDFI technique reported in a previous work(Chen J, Gao K, Ge X, et al.2013 Opt. Lett. 38 2068). In addition, the details of the newly invented algorithm are explained, which is able to calculate the intensity of any pixel on the image plane rapidly and reliably.
基金Project supported by the Natural Science Foundation of Liaoning ProvinceChina, the National Natural Science Foundation of China (Grant No. 29875030)the Excellent Young Scientist Award from the National Natural Science Foundation of China. (Grant
文摘Three chiral compounds were successfully separated in a short time with two enantiomer separation models on packed-capillary electrochromatography ( CEC ) . (i) 75 μm I.D. capillaries were packed with 5 μm β-cyclodextrin (β-CD) chiral stationary phase (CSP) . Effects of voltage, pH and concentration of organic modifier on electroosmotic flow (EOF) and chiral separations were investigated systematically. Enantiomers of a neutral compound (benzoin) and a neutral drug (mephenytoin) were separated within a short time with high efficiency. Efficiency of 32 000 theoretical plates per meter and resolution (R) of 1.42 were achieved for enantiomers of benzoin using a βCD packed column with 6.2 cm packed length. Efficiency of 45 000 theoretical plates per meter and R of 3 .40 were obtained for enantiomers of mephenytoin. Especially, the enantiomer separation of mephenytion was performed in just 3.4 min with R, of 2.60. (ii) 75 μm I.D. capillary was packed with octadecylsilica particles (ODS) . Chiral separation of a basic drug, propra-nolol, was studied with chiral agent, via addition of the dimethyl-β-cyclodextrin (DM β-CD ) directly into the mobile phase on this column. Baseline separation and efficiency of 81 000 theoretical plates per meter were achieved for propra-nolol.
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.61622107 and 61871146)
文摘High-resolution of Inverse Synthetic Aperture Radar (ISAR) in the azimuth direction can be achieved by increasing the coherent accumulation angle of the target rotation.However, in practice, the coherent accumulation angle may be small.In this paper, a novel algorithm for high-resolution ISAR imaging based on the SParse Iterative Covariance-based Estimation (SPICE) is proposed.As a nonparametric sparse spectrum estimation algorithm, the SPICE algorithm does not need to set any parameters and it converges globally, so it can realize high quality imaging with limited measurements.In addition, a fast implementation of the SPICE algorithm based on the Gohberg-Semencul (G-S) factorization is introduced in this paper.The ISAR imaging of simulated and measured data was analyzed to illustrate the effectiveness of the novel approach.
