Among Synthetic Aperture Radar(SAR)image formation algorithms,the chirp scaling algorithm(CSA)is computationally highly efficient and has been practically used.In this paper,how to implement the subaperture extended C...Among Synthetic Aperture Radar(SAR)image formation algorithms,the chirp scaling algorithm(CSA)is computationally highly efficient and has been practically used.In this paper,how to implement the subaperture extended CSA in a high resolution spotlight mode SAR is studied in detail.The procedures such as subaperture processing and azimuth processing are discussed.According to the problems presented when using the method(A.Moreira,et al,1996)to process spotlight SAR data,full formula expressions suitable for high squinted angles is presented.While point target simulation is analyzed,the method is validated by E SAR raw data.The results can be directly implemented in the design of SAR processors.展开更多
Conventional synthetic aperture radar（SAR） systems cannot achieve both highresolution and wide-swath imaging simultaneously.This problem can be mitigated by employing multiple-azimuth-phases（MAPs） technology for s...Conventional synthetic aperture radar（SAR） systems cannot achieve both highresolution and wide-swath imaging simultaneously.This problem can be mitigated by employing multiple-azimuth-phases（MAPs） technology for spaceborne sliding spotlight SAR systems.However, traditional imaging algorithms have met challenges to process the data accurately, due to range model error, MAPs data reconstruction problem, high-order cross-coupling phase error and variation of Doppler parameters along the azimuth direction.Therefore, an improved imaging algorithm is proposed for solving the above problems.Firstly, a modified hyperbolic range equation（MHRE） is proposed by introducing a cubic term into the traditional hyperbolic range equation（THRE）.And two curved orbit correction methods are derived based on the proposed range model.Then, a MAPs sliding spotlight data reconstruction method is introduced, which solves the spectral aliasing problem by a de-rotation operation.Finally, high-order cross-coupling phases and variation of Doppler parameters are analyzed and the corresponding compensation methods are proposed.Simulation results for point-target scene are provided to verify the effectiveness of the proposed algorithm.展开更多
This paper investigates a novel approach based on the deramping technique for squinted sliding spotlight Synthetic Aperture Radar (SAR) imaging to resolve the azimuth spectrum aliasing problem. First of all, the prope...This paper investigates a novel approach based on the deramping technique for squinted sliding spotlight Synthetic Aperture Radar (SAR) imaging to resolve the azimuth spectrum aliasing problem. First of all, the properties of the azimuth spectrum and the squint angle impacts on the azimuth spectrum aliasing problem are analyzed. Based on the analysis result, an operation of filtering is added to the azimuth preprocessing step of traditional Two-Step Focusing Approach (TSPA) to resolve the azimuth folding problem and remove the influence of the squint angle on the azimuth spectrum aliasing problem. Then, a modified Range Migration Algorithm (RMA) is performed to obtain the precise focused image. Furthermore, the focused SAR image folding problem of traditional TSPA is illuminated in this paper. An azimuth post-processing step is proposed to unfold the aliased SAR image. Simulation experiment results prove that the proposed approach can solve the spectrum aliasing problem and process squinted sliding spotlight data efficiently.展开更多
A system impulse response with low sidelobes is critical in synthetic aperture radar（SAR） images because sidelobes contribute to noise and interfere with nearby scatterers. However,the conventional tricks of sidelob...A system impulse response with low sidelobes is critical in synthetic aperture radar（SAR） images because sidelobes contribute to noise and interfere with nearby scatterers. However,the conventional tricks of sidelobe suppression are unable to be exactly applied to the case of spaceborne sliding spotlight SAR due to great azimuth shifts in both time and frequency domains. In this paper, an extended chirp scaling algorithm is presented for spaceborne sliding spotlight SAR data imaging. The proposed algorithm firstly uses the spectral analysis（SPECAN） technique to avoid the azimuth spectrum folding effect and then employs the chirp scaling（CS） algorithm to achieve data focusing, i.e., the so-called two-step approach. To suppress the sidelobe level, an efficient strategy for the azimuth spectral weighting which only involves matrix multiplications and short fast Fourier transformations（FFTs） is proposed, which is a post-process executed on the focused SAR image and particularly simple to be implemented. The SAR image processed by the proposed extended CS algorithm is very precise and perfectly phase-preserving. In the end, computer simulation results verify the analysis and confirm the validity of the proposed algorithm.展开更多
Spinal cord injury（SCI）with consecutive paralysis below the lesion level is a severe disorder affecting the patient for the rest of his or her life.So far,there is no known fundamental intervention strategy for effi...Spinal cord injury（SCI）with consecutive paralysis below the lesion level is a severe disorder affecting the patient for the rest of his or her life.So far,there is no known fundamental intervention strategy for efficiently helping those patients regain their motor abilities,despite intense research in this area.Thus,effective treatment for those patients is still an open question. A spinal cord injury is accompanied by a prima- ry, severe and irreversible neuronal cell death in the trauma region, fol- lowed by a secondary extensive cell necrosis in the lesion surrounding areas. Nevertheless, recent studies indicate that regeneration after spinal cord injury could be possible if three substantial steps are fulfilled： （1） reduction of the inhibitory environment at the SCI lesion site, （2） iden- tification of a neural substrate to establish new spinal circuits, and （3） support of these circuits to form permanent, functional motor, sensory, or autonomic connections （Dru and Hoh, 2015）.展开更多
This paper first studies the phase errors for fine-resolution spotlight mode SAR imaging and decomposes the phase errors into two kinds, one is caused by translation and the other by rotation. Mathematical analysis an...This paper first studies the phase errors for fine-resolution spotlight mode SAR imaging and decomposes the phase errors into two kinds, one is caused by translation and the other by rotation. Mathematical analysis and computer simulations show the above mentioned motion kinds and their corresponding damages on spotlight mode SAR imaging. Based on this analysis, a single PPP is introduced for spotlight mode SAR imaging with the PFA on the assumption that relative rotation between APC and imaged scene is uniform. The selected single point is used first to correct the quadratic and higher order phase errors and then to adjust the linear errors. After this compensation, the space-invariant phase errors caused by translation are almost corrected. Finally results are presented with the simulated data.展开更多
For a synthetic aperture radar（SAR） system mounted on a geostationary Earth orbit（GEO） satellite, the track can be curvilinear. Thus, a bistatic SAR system based up on geostationary transmitter and ＂receive-only...For a synthetic aperture radar（SAR） system mounted on a geostationary Earth orbit（GEO） satellite, the track can be curvilinear. Thus, a bistatic SAR system based up on geostationary transmitter and ＂receive-only＂ SAR system onboard airplanes, namely GEO spaceborne-airborne bistatic（GEO SA-Bi SAR）, is significantly different from the traditional bistatic SAR. This paper mainly studies the resolution characteristic of the sliding spotlight GEO SA-Bi SAR system. Firstly, the common azimuth coverage and coherent accumulated time are theoretically analyzed in detail. Then,based on the gradient method, the accurate two dimensional resolution of a GEO SA-Bi SAR system is analytically calculated. Finally, the simulation data show the correctness and effectiveness of the proposed resolution analysis method.展开更多
FEBRUARY,2016 Regulations Concerning Menstrual Pain Leave a Step in the Right Direction Women in Anhui Province can take 1-2 days off when suffering menstrual pain so long as they provide a medical certificate,accordi...FEBRUARY,2016 Regulations Concerning Menstrual Pain Leave a Step in the Right Direction Women in Anhui Province can take 1-2 days off when suffering menstrual pain so long as they provide a medical certificate,according to the latest labor regulations established by the Anhui provincial government.Anhui is not the only province to take this stance.Other regions,such as Jiangsu Province and Guangdong Province,are also展开更多
Advances in liver transplantation for hepatocellular carcinoma Dr.Ronald W.Busuttil from University of California,Los Angles,described progress in liver transplantation for hepatocellular carcinoma(HCC).Three
Li Ming(李明)Prof.Li is a tenured professor in the School of Materials Science and Engineering at Shanghai Jiao Tong University,and the founder of the Institute of Electronics Materials and Technology.He received his ...Li Ming(李明)Prof.Li is a tenured professor in the School of Materials Science and Engineering at Shanghai Jiao Tong University,and the founder of the Institute of Electronics Materials and Technology.He received his Ph D degree from Kyushu Institute of Technology(Japan)in 1998.He then worked in a Japanese manufacturing company Mitsui High-Tec Inc.for many years.Currently,his research interest mainly focused 3D packaging materials and technology(lead-free solder,interconnection,low temperature bonding),nanostructured materials and functional thin films preparation routed by electrochemical method(electrodeposition,electro-grafting).展开更多
Renjie Chen (陈人杰)Prof. Chen is a full professor, doctoral supervisor of Beijing Institute of Technology. He is the director of Innovation Center for Advanced Energy Materials and Smart Batteries of Advanced Technol...Renjie Chen (陈人杰)Prof. Chen is a full professor, doctoral supervisor of Beijing Institute of Technology. He is the director of Innovation Center for Advanced Energy Materials and Smart Batteries of Advanced Technology Research Institute.展开更多
Visit China ’97 will be introduced soonthrough the joint efforts of the NationalTourism Administration and the CivilAviation Administration of China ( CAAC )following the first success of China Tour ’92,which they a...Visit China ’97 will be introduced soonthrough the joint efforts of the NationalTourism Administration and the CivilAviation Administration of China ( CAAC )following the first success of China Tour ’92,which they also sponsored. It is a common promotional methodto hold tourist years in international tourismcircles and thus in most cases, achievegratifying results. To promote the integrationof China’s tourism with the internationalmarket, the National Tourism Administrationhas launched a series of promotional activities,including the ’93 China Scenery Tour,展开更多
Real estate has been one of the fastest growing sectors in China since its opening to the outside world. The sustained, steady growth of the national economy has provided favourable conditions for the rapid growth of ...Real estate has been one of the fastest growing sectors in China since its opening to the outside world. The sustained, steady growth of the national economy has provided favourable conditions for the rapid growth of the real estate industry, and the higher profits anticipated have attracted a large volume of overseas capital into the industry. Various real estate companies have flourished, and a number of luxury hotels, villas and holiday展开更多
基金National Natural Science F oundation of china(68931040)
文摘Among Synthetic Aperture Radar(SAR)image formation algorithms,the chirp scaling algorithm(CSA)is computationally highly efficient and has been practically used.In this paper,how to implement the subaperture extended CSA in a high resolution spotlight mode SAR is studied in detail.The procedures such as subaperture processing and azimuth processing are discussed.According to the problems presented when using the method(A.Moreira,et al,1996)to process spotlight SAR data,full formula expressions suitable for high squinted angles is presented.While point target simulation is analyzed,the method is validated by E SAR raw data.The results can be directly implemented in the design of SAR processors.
基金supported by the National Natural Science Foundation of China (No.61132006)
文摘Conventional synthetic aperture radar（SAR） systems cannot achieve both highresolution and wide-swath imaging simultaneously.This problem can be mitigated by employing multiple-azimuth-phases（MAPs） technology for spaceborne sliding spotlight SAR systems.However, traditional imaging algorithms have met challenges to process the data accurately, due to range model error, MAPs data reconstruction problem, high-order cross-coupling phase error and variation of Doppler parameters along the azimuth direction.Therefore, an improved imaging algorithm is proposed for solving the above problems.Firstly, a modified hyperbolic range equation（MHRE） is proposed by introducing a cubic term into the traditional hyperbolic range equation（THRE）.And two curved orbit correction methods are derived based on the proposed range model.Then, a MAPs sliding spotlight data reconstruction method is introduced, which solves the spectral aliasing problem by a de-rotation operation.Finally, high-order cross-coupling phases and variation of Doppler parameters are analyzed and the corresponding compensation methods are proposed.Simulation results for point-target scene are provided to verify the effectiveness of the proposed algorithm.
文摘This paper investigates a novel approach based on the deramping technique for squinted sliding spotlight Synthetic Aperture Radar (SAR) imaging to resolve the azimuth spectrum aliasing problem. First of all, the properties of the azimuth spectrum and the squint angle impacts on the azimuth spectrum aliasing problem are analyzed. Based on the analysis result, an operation of filtering is added to the azimuth preprocessing step of traditional Two-Step Focusing Approach (TSPA) to resolve the azimuth folding problem and remove the influence of the squint angle on the azimuth spectrum aliasing problem. Then, a modified Range Migration Algorithm (RMA) is performed to obtain the precise focused image. Furthermore, the focused SAR image folding problem of traditional TSPA is illuminated in this paper. An azimuth post-processing step is proposed to unfold the aliased SAR image. Simulation experiment results prove that the proposed approach can solve the spectrum aliasing problem and process squinted sliding spotlight data efficiently.
基金supported by the National Natural Science Foundation of China(No.41301450)the Fundamental Research Funds for the Central Universities of China(No.QN2013066)the Exclusive Talent Funds of Northwest A&F University of China(No.Z111021302)
文摘A system impulse response with low sidelobes is critical in synthetic aperture radar（SAR） images because sidelobes contribute to noise and interfere with nearby scatterers. However,the conventional tricks of sidelobe suppression are unable to be exactly applied to the case of spaceborne sliding spotlight SAR due to great azimuth shifts in both time and frequency domains. In this paper, an extended chirp scaling algorithm is presented for spaceborne sliding spotlight SAR data imaging. The proposed algorithm firstly uses the spectral analysis（SPECAN） technique to avoid the azimuth spectrum folding effect and then employs the chirp scaling（CS） algorithm to achieve data focusing, i.e., the so-called two-step approach. To suppress the sidelobe level, an efficient strategy for the azimuth spectral weighting which only involves matrix multiplications and short fast Fourier transformations（FFTs） is proposed, which is a post-process executed on the focused SAR image and particularly simple to be implemented. The SAR image processed by the proposed extended CS algorithm is very precise and perfectly phase-preserving. In the end, computer simulation results verify the analysis and confirm the validity of the proposed algorithm.
基金supported by DFG Grant KFO 213 and the "ElseKr?ner-Fresenius-Stiftung" to JG
文摘Spinal cord injury（SCI）with consecutive paralysis below the lesion level is a severe disorder affecting the patient for the rest of his or her life.So far,there is no known fundamental intervention strategy for efficiently helping those patients regain their motor abilities,despite intense research in this area.Thus,effective treatment for those patients is still an open question. A spinal cord injury is accompanied by a prima- ry, severe and irreversible neuronal cell death in the trauma region, fol- lowed by a secondary extensive cell necrosis in the lesion surrounding areas. Nevertheless, recent studies indicate that regeneration after spinal cord injury could be possible if three substantial steps are fulfilled： （1） reduction of the inhibitory environment at the SCI lesion site, （2） iden- tification of a neural substrate to establish new spinal circuits, and （3） support of these circuits to form permanent, functional motor, sensory, or autonomic connections （Dru and Hoh, 2015）.
基金Supported by the Aeronautic Scientific Foundation(No.98F5118)
文摘This paper first studies the phase errors for fine-resolution spotlight mode SAR imaging and decomposes the phase errors into two kinds, one is caused by translation and the other by rotation. Mathematical analysis and computer simulations show the above mentioned motion kinds and their corresponding damages on spotlight mode SAR imaging. Based on this analysis, a single PPP is introduced for spotlight mode SAR imaging with the PFA on the assumption that relative rotation between APC and imaged scene is uniform. The selected single point is used first to correct the quadratic and higher order phase errors and then to adjust the linear errors. After this compensation, the space-invariant phase errors caused by translation are almost corrected. Finally results are presented with the simulated data.
基金supported by the National Natural Science Foundation of China(61271342)
文摘For a synthetic aperture radar（SAR） system mounted on a geostationary Earth orbit（GEO） satellite, the track can be curvilinear. Thus, a bistatic SAR system based up on geostationary transmitter and ＂receive-only＂ SAR system onboard airplanes, namely GEO spaceborne-airborne bistatic（GEO SA-Bi SAR）, is significantly different from the traditional bistatic SAR. This paper mainly studies the resolution characteristic of the sliding spotlight GEO SA-Bi SAR system. Firstly, the common azimuth coverage and coherent accumulated time are theoretically analyzed in detail. Then,based on the gradient method, the accurate two dimensional resolution of a GEO SA-Bi SAR system is analytically calculated. Finally, the simulation data show the correctness and effectiveness of the proposed resolution analysis method.
文摘FEBRUARY,2016 Regulations Concerning Menstrual Pain Leave a Step in the Right Direction Women in Anhui Province can take 1-2 days off when suffering menstrual pain so long as they provide a medical certificate,according to the latest labor regulations established by the Anhui provincial government.Anhui is not the only province to take this stance.Other regions,such as Jiangsu Province and Guangdong Province,are also
文摘Advances in liver transplantation for hepatocellular carcinoma Dr.Ronald W.Busuttil from University of California,Los Angles,described progress in liver transplantation for hepatocellular carcinoma(HCC).Three
文摘Li Ming(李明)Prof.Li is a tenured professor in the School of Materials Science and Engineering at Shanghai Jiao Tong University,and the founder of the Institute of Electronics Materials and Technology.He received his Ph D degree from Kyushu Institute of Technology(Japan)in 1998.He then worked in a Japanese manufacturing company Mitsui High-Tec Inc.for many years.Currently,his research interest mainly focused 3D packaging materials and technology(lead-free solder,interconnection,low temperature bonding),nanostructured materials and functional thin films preparation routed by electrochemical method(electrodeposition,electro-grafting).
文摘Renjie Chen (陈人杰)Prof. Chen is a full professor, doctoral supervisor of Beijing Institute of Technology. He is the director of Innovation Center for Advanced Energy Materials and Smart Batteries of Advanced Technology Research Institute.
文摘Visit China ’97 will be introduced soonthrough the joint efforts of the NationalTourism Administration and the CivilAviation Administration of China ( CAAC )following the first success of China Tour ’92,which they also sponsored. It is a common promotional methodto hold tourist years in international tourismcircles and thus in most cases, achievegratifying results. To promote the integrationof China’s tourism with the internationalmarket, the National Tourism Administrationhas launched a series of promotional activities,including the ’93 China Scenery Tour,
文摘Real estate has been one of the fastest growing sectors in China since its opening to the outside world. The sustained, steady growth of the national economy has provided favourable conditions for the rapid growth of the real estate industry, and the higher profits anticipated have attracted a large volume of overseas capital into the industry. Various real estate companies have flourished, and a number of luxury hotels, villas and holiday
