Bistatic forward-looking synthetic aperture radar（SAR） has many advantages and applications owing to its twodimensional imaging capability.There could be various imaging configurations because of the geometric flexi...Bistatic forward-looking synthetic aperture radar（SAR） has many advantages and applications owing to its twodimensional imaging capability.There could be various imaging configurations because of the geometric flexibility of bistatic platforms,resulting in kinds of models built independently among which there could be some similar even the same motion features.Comprehensive research on such systems in a more comprehensive and general point of view is required to address their difference and consistency.Property analysis of bistatic forwardlooking SAR with arbitrary geometry is achieved including stripmap and spotlight modes on airborne platform,missile-borne platform,and hybrid platform of both.Emphasis is placed on azimuth space variance of some key parameters significantly affecting the subsequent imaging processing,based on which the frequency spectra are further described and compared considering respective features of different platforms for frequency imaging algorithm developing.Simulation results confirm the effectiveness and correctness of our analysis.展开更多
The azimuth resolution improvement problem is solved via a coherent combination of synthetic aperture radar （SAR） ima-ges with the quasi-non-overlapped Doppler bandwidth. Prior to the spectra combination, SAR images...The azimuth resolution improvement problem is solved via a coherent combination of synthetic aperture radar （SAR） ima-ges with the quasi-non-overlapped Doppler bandwidth. Prior to the spectra combination, SAR images should be coregistered, while phase biases induced by topography, atmospheric propagation delays and baseline measurement errors should be calibrated. However, the coregistration accuracy suffers from large Doppler decorrelation caused by the quasi-non-overlapped Doppler band-width. Furthermore, the method used to estimate phase biases from interferogram of azimuth prefiltered SAR image pairs wil fail when there is no overlapped spectrum. The fringe simulation and maximum sharpness optimization are adopted to deal with the problems. Accordingly, a novel algorithm to coherently synthesize SAR images is presented. The experiment with the Terra SAR X-band （TerraSAR-X） satel ite data validates the performance of the presented method.展开更多
SARS-CoV-2 has been demonstrated to be highly susceptible to neuron-and glial-like cells,1 but there is no consensus regarding how the virus affects neurons following neuroinvasion.It is therefore unknown if and how S...SARS-CoV-2 has been demonstrated to be highly susceptible to neuron-and glial-like cells,1 but there is no consensus regarding how the virus affects neurons following neuroinvasion.It is therefore unknown if and how SARS-CoV-2 maintains the homeostasis of neuronal cells.Herein,we revealed that the receptor-binding domain(RBD)of the SARS-CoV-2 spike protein acted as an extracellular remodeling component to undermine epigenetic regulation,perturbnascentRNA(nsRNA)transcription,promote mitochondrial biogenesis,and increase cellular viability in SH-SY5Y cells.展开更多
In this viewpoint,recent hot topics in the photovoltaic community,interdigitated back contact(IBC)cells,are systematically reviewed from the view of device configuration.Two categories of IBC designs on the most popul...In this viewpoint,recent hot topics in the photovoltaic community,interdigitated back contact(IBC)cells,are systematically reviewed from the view of device configuration.Two categories of IBC designs on the most popular perovskite solar cells(PSCs)were discussed,and a planar back-contact perovskite module was first proposed.The device configuration,fabrication methods,working mechanism,optimization strategies,and future development directions of this novel PSC module were put forward to show its superiorities in the module performance,processing difficulty,and extensible functionality among present perovskite modules,presenting promising potential to improve the competitiveness of perovskite technology in the photovoltaic market.展开更多
Automatic target recognition （ATR） is an important function for modern radar. High resolution range profile （HRRP） of target contains target struc- ture signatures, such as target size, scatterer distribu- tion, e...Automatic target recognition （ATR） is an important function for modern radar. High resolution range profile （HRRP） of target contains target struc- ture signatures, such as target size, scatterer distribu- tion, etc, which is a promising signature for ATR. Sta- tistical modeling of target HRRPs is the key stage for HRRP statistical recognition, including model selection and parameter estimation. For statistical recognition al- gorithms, it is generally assumed that the test samples follow the same distribution model as that of the train- ing data. Since the signal-to-noise ratio （SNR） of the received HRRP is a function of target distance, the as- sumption may be not met in practice. In this paper, we present a robust method for HRRP statistical recogni- tion when SNR of test HRRP is lower than that of train- ing samples. The noise is assumed independent Gaus- sian distributed, while HRRP is modeled by probabilistic principal component analysis （PPCA） model. Simulated experiments based on measured data show the effective- ness of the proposed method.展开更多
Radar high-resolution range profiles(HRRPs)are typical high-dimensional and interdimension dependently distributed data,the statistical modeling of which is a challenging task for HRRP-based target recognition.Supposi...Radar high-resolution range profiles(HRRPs)are typical high-dimensional and interdimension dependently distributed data,the statistical modeling of which is a challenging task for HRRP-based target recognition.Supposing that HRRP samples are independent and jointly Gaussian distributed,a recent work[Du L,Liu H W,Bao Z.IEEE Transactions on Signal Processing,2008,56(5):1931–1944]applied factor analysis(FA)to model HRRP data with a two-phase approach for model selection,which achieved satisfactory recognition performance.The theoretical analysis and experimental results reveal that there exists high temporal correlation among adjacent HRRPs.This paper is thus motivated to model the spatial and temporal structure of HRRP data simultaneously by employing temporal factor analysis(TFA)model.For a limited size of high-dimensional HRRP data,the two-phase approach for parameter learning and model selection suffers from intensive computation burden and deteriorated evaluation.To tackle these problems,this work adopts the Bayesian Ying-Yang(BYY)harmony learning that has automatic model selection ability during parameter learning.Experimental results show stepwise improved recognition and rejection performances from the twophase learning based FA,to the two-phase learning based TFA and to the BYY harmony learning based TFA with automatic model selection.In addition,adding many extra free parameters to the classic FA model and thus becoming even worse in identifiability,the model of a general linear dynamical system is even inferior to the classic FA model.展开更多
The frequency modulated continuous wave(FMCW)radar has the characteristics of low probability of interception,good hidden property and the ability to counter anti-radiation missiles.This paper proposes a new method fo...The frequency modulated continuous wave(FMCW)radar has the characteristics of low probability of interception,good hidden property and the ability to counter anti-radiation missiles.This paper proposes a new method for high-speed ground moving target detection(GMTD)using triangular modulation FMCW.According to the characteristic of the opposite range shift induced by the upslope and downslope modulation FMCW,the upslope and downslope are imaged,respectively.After compensation of continuous motion of the platform and time difference between upslope and downslope signals for imaging,the moving target can be detected through displaced phase center antenna(DPCA)technology.When the moving target is detected,the moving target image is extracted,and correlation processing is used to obtain the range shift,which can be used to estimate the target radial velocity,and further to find the real position of the target.The effectiveness of this method is verified by the result of computer simulation.展开更多
基金supported by the National Natural Science Foundation of China(6100121161303035+1 种基金61471283)the Fundamental Research Funds for the Central Universities(K5051202016)
文摘Bistatic forward-looking synthetic aperture radar（SAR） has many advantages and applications owing to its twodimensional imaging capability.There could be various imaging configurations because of the geometric flexibility of bistatic platforms,resulting in kinds of models built independently among which there could be some similar even the same motion features.Comprehensive research on such systems in a more comprehensive and general point of view is required to address their difference and consistency.Property analysis of bistatic forwardlooking SAR with arbitrary geometry is achieved including stripmap and spotlight modes on airborne platform,missile-borne platform,and hybrid platform of both.Emphasis is placed on azimuth space variance of some key parameters significantly affecting the subsequent imaging processing,based on which the frequency spectra are further described and compared considering respective features of different platforms for frequency imaging algorithm developing.Simulation results confirm the effectiveness and correctness of our analysis.
基金supported by the National Natural Science Foundationof China(41001282)
文摘The azimuth resolution improvement problem is solved via a coherent combination of synthetic aperture radar （SAR） ima-ges with the quasi-non-overlapped Doppler bandwidth. Prior to the spectra combination, SAR images should be coregistered, while phase biases induced by topography, atmospheric propagation delays and baseline measurement errors should be calibrated. However, the coregistration accuracy suffers from large Doppler decorrelation caused by the quasi-non-overlapped Doppler band-width. Furthermore, the method used to estimate phase biases from interferogram of azimuth prefiltered SAR image pairs wil fail when there is no overlapped spectrum. The fringe simulation and maximum sharpness optimization are adopted to deal with the problems. Accordingly, a novel algorithm to coherently synthesize SAR images is presented. The experiment with the Terra SAR X-band （TerraSAR-X） satel ite data validates the performance of the presented method.
基金supported by grants from The National Natural Science Foundation of China(No.81971132,82271306)the Sichuan Science and Technology Program(China)(No.2021ZYD0106,2021ZYD0091,22ZDYF3783,2022YFS0615,2023YFH0069,2023NSFSC0028,2023NSFSC1559)+1 种基金Project of Luzhou Science and Technology Bureau(No.2021LZXNYDP01,2021LZXNYD-Z05)Luzhou Government-Southwest Medical University Strategic Cooperation Project and Southwest Medical University Project(Sichuan,China)(No.2021ZKQN058,2020ZRQNB072,2021ZKZD013,2021ZKQN041).
文摘SARS-CoV-2 has been demonstrated to be highly susceptible to neuron-and glial-like cells,1 but there is no consensus regarding how the virus affects neurons following neuroinvasion.It is therefore unknown if and how SARS-CoV-2 maintains the homeostasis of neuronal cells.Herein,we revealed that the receptor-binding domain(RBD)of the SARS-CoV-2 spike protein acted as an extracellular remodeling component to undermine epigenetic regulation,perturbnascentRNA(nsRNA)transcription,promote mitochondrial biogenesis,and increase cellular viability in SH-SY5Y cells.
基金China Postdoctoral Science Foundation(2023M731476,2023T160286)Beijing Postdoctoral Research Foundation.
文摘In this viewpoint,recent hot topics in the photovoltaic community,interdigitated back contact(IBC)cells,are systematically reviewed from the view of device configuration.Two categories of IBC designs on the most popular perovskite solar cells(PSCs)were discussed,and a planar back-contact perovskite module was first proposed.The device configuration,fabrication methods,working mechanism,optimization strategies,and future development directions of this novel PSC module were put forward to show its superiorities in the module performance,processing difficulty,and extensible functionality among present perovskite modules,presenting promising potential to improve the competitiveness of perovskite technology in the photovoltaic market.
文摘Automatic target recognition （ATR） is an important function for modern radar. High resolution range profile （HRRP） of target contains target struc- ture signatures, such as target size, scatterer distribu- tion, etc, which is a promising signature for ATR. Sta- tistical modeling of target HRRPs is the key stage for HRRP statistical recognition, including model selection and parameter estimation. For statistical recognition al- gorithms, it is generally assumed that the test samples follow the same distribution model as that of the train- ing data. Since the signal-to-noise ratio （SNR） of the received HRRP is a function of target distance, the as- sumption may be not met in practice. In this paper, we present a robust method for HRRP statistical recogni- tion when SNR of test HRRP is lower than that of train- ing samples. The noise is assumed independent Gaus- sian distributed, while HRRP is modeled by probabilistic principal component analysis （PPCA） model. Simulated experiments based on measured data show the effective- ness of the proposed method.
基金The work described in this paper was supported by a grant of the General Research Fund(GRF)from the Research Grant Council of the Hong Kong SAR(No.CUHK4180/10E)the National Natural Science Foundation of China(Grant Nos.60901067 and 61001212)+1 种基金Program for New Century Excellent Talents in University(No.NCET-09-0630)Program for Changjiang Scholars and Innovative Research Team in University(No.IRT0954),and the Fundamental Research Funds for the Central Universities.
文摘Radar high-resolution range profiles(HRRPs)are typical high-dimensional and interdimension dependently distributed data,the statistical modeling of which is a challenging task for HRRP-based target recognition.Supposing that HRRP samples are independent and jointly Gaussian distributed,a recent work[Du L,Liu H W,Bao Z.IEEE Transactions on Signal Processing,2008,56(5):1931–1944]applied factor analysis(FA)to model HRRP data with a two-phase approach for model selection,which achieved satisfactory recognition performance.The theoretical analysis and experimental results reveal that there exists high temporal correlation among adjacent HRRPs.This paper is thus motivated to model the spatial and temporal structure of HRRP data simultaneously by employing temporal factor analysis(TFA)model.For a limited size of high-dimensional HRRP data,the two-phase approach for parameter learning and model selection suffers from intensive computation burden and deteriorated evaluation.To tackle these problems,this work adopts the Bayesian Ying-Yang(BYY)harmony learning that has automatic model selection ability during parameter learning.Experimental results show stepwise improved recognition and rejection performances from the twophase learning based FA,to the two-phase learning based TFA and to the BYY harmony learning based TFA with automatic model selection.In addition,adding many extra free parameters to the classic FA model and thus becoming even worse in identifiability,the model of a general linear dynamical system is even inferior to the classic FA model.
基金supported by the National Natural Science Foundation of China (Grant No.60502044).
文摘The frequency modulated continuous wave(FMCW)radar has the characteristics of low probability of interception,good hidden property and the ability to counter anti-radiation missiles.This paper proposes a new method for high-speed ground moving target detection(GMTD)using triangular modulation FMCW.According to the characteristic of the opposite range shift induced by the upslope and downslope modulation FMCW,the upslope and downslope are imaged,respectively.After compensation of continuous motion of the platform and time difference between upslope and downslope signals for imaging,the moving target can be detected through displaced phase center antenna(DPCA)technology.When the moving target is detected,the moving target image is extracted,and correlation processing is used to obtain the range shift,which can be used to estimate the target radial velocity,and further to find the real position of the target.The effectiveness of this method is verified by the result of computer simulation.
