Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306150
Wen‐Hua Tu
A microstrip-parallel strip-fed circularly polarized spiral antenna is investigated. A wideband microstrip to parallel strip transition is designed in order to feed the spiral antenna. The transition shows a back-to-back return loss of better than 10 dB from 0.045 to 20 GHz except for a ripple at 2 GHz, while the back-to-back insertion loss is less than 2.4 dB. The final antenna shows a return loss of better than 10 dB from 2.5 to 13.5 GHz. The antenna axial ratio is better than 2.2 dB from 5 to 12 GHz.
{"title":"Wideband circularly polarized microstrip-parallel strip-fed spiral antenna","authors":"Wen‐Hua Tu","doi":"10.1109/APSAR.2015.7306150","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306150","url":null,"abstract":"A microstrip-parallel strip-fed circularly polarized spiral antenna is investigated. A wideband microstrip to parallel strip transition is designed in order to feed the spiral antenna. The transition shows a back-to-back return loss of better than 10 dB from 0.045 to 20 GHz except for a ripple at 2 GHz, while the back-to-back insertion loss is less than 2.4 dB. The final antenna shows a return loss of better than 10 dB from 2.5 to 13.5 GHz. The antenna axial ratio is better than 2.2 dB from 5 to 12 GHz.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127625597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306237
Lei Yang, Song Zhou, G. Bi
In this paper, we investigate the mechanism of Fast Factorized Back-projection (FFBP) algorithm by revealing the relationship between the echoed signal and the spectrum of synthetic aperture radar (SAR) image projected on different coordinate systems. Based on the spectral analysis, a modified FFBP algorithm for squint ultra-wide bandwidth (UWB) SAR imaging is presented. Comparing with the conventional FFBP algorithm, the sub-aperture images are recursively mapped on pseudo polar coordinate rather than original polar coordinate. With the pseudo polar coordinate, the spectrum of sub-aperture SAR image is compacted in a narrower range. Thus only a low Nyquist sample rate is applied to the BP maps which dramatically reduces the redundant back-projections in operation. Simulation results are presented to validate the effectiveness of the proposed method in squint UWB-SAR case.
{"title":"A modified fast factorized back-projection algorithm for squint UWB-SAR imaging","authors":"Lei Yang, Song Zhou, G. Bi","doi":"10.1109/APSAR.2015.7306237","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306237","url":null,"abstract":"In this paper, we investigate the mechanism of Fast Factorized Back-projection (FFBP) algorithm by revealing the relationship between the echoed signal and the spectrum of synthetic aperture radar (SAR) image projected on different coordinate systems. Based on the spectral analysis, a modified FFBP algorithm for squint ultra-wide bandwidth (UWB) SAR imaging is presented. Comparing with the conventional FFBP algorithm, the sub-aperture images are recursively mapped on pseudo polar coordinate rather than original polar coordinate. With the pseudo polar coordinate, the spectrum of sub-aperture SAR image is compacted in a narrower range. Thus only a low Nyquist sample rate is applied to the BP maps which dramatically reduces the redundant back-projections in operation. Simulation results are presented to validate the effectiveness of the proposed method in squint UWB-SAR case.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128279804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306168
C. Kee, F. Hu, Chao‐Fu Wang, T. Chia
Generating high resolution SAR image of an object typically requires its scattered field data over a large number of aspect angles and frequencies, which is very time consuming to obtain. This paper discusses the implementation of the PO-SBR method on GPU to efficiently compute the massive scattered field data required for SAR application.
{"title":"Accelerating PO-SBR for SAR application","authors":"C. Kee, F. Hu, Chao‐Fu Wang, T. Chia","doi":"10.1109/APSAR.2015.7306168","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306168","url":null,"abstract":"Generating high resolution SAR image of an object typically requires its scattered field data over a large number of aspect angles and frequencies, which is very time consuming to obtain. This paper discusses the implementation of the PO-SBR method on GPU to efficiently compute the massive scattered field data required for SAR application.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130944069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306207
Venkata Kishore Kothapudi, Vijay Kumar
In this letter the design and simulation of an 0.43GHz P/UHF band microstrip patch antenna as single element, 2, 4, 8 & 16-element linear array using RT/duroid 6002 substrate was proposed. An inter-element spacing of 0.73λ for limited scan angle coverage. Wind profiling radar operating in Doppler beam swinging mode and spaced antenna drift technique mode needs to have a large aperture antenna array in order to get the narrow pencil beam is required for wind speed and direction accuracy. To meet the above requirements a microstrip patch antenna single element is used to design a 2, 4, 8 & 16-element linear antenna array for Tropospheric Wind Profiling Radar Operating at 0.43GHz. Conception details and simulation results are also given for the both single element & 16-element linear antenna array. The designed and simulated results are presented. A full wave electromagnetic simulator zeland IE3D V12.02 is used to validate the design approach. The simulated results below present are valid over the 0.43GHz band and the simulated parameters contains the VSWR, Return loss, impedance, gain, directivity, efficiency and elevation gain patterns.
{"title":"Design of 0.73λ inter-element spacing linear array for 0.43GHz P/UHF-band tropospheric radar wind profiler","authors":"Venkata Kishore Kothapudi, Vijay Kumar","doi":"10.1109/APSAR.2015.7306207","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306207","url":null,"abstract":"In this letter the design and simulation of an 0.43GHz P/UHF band microstrip patch antenna as single element, 2, 4, 8 & 16-element linear array using RT/duroid 6002 substrate was proposed. An inter-element spacing of 0.73λ for limited scan angle coverage. Wind profiling radar operating in Doppler beam swinging mode and spaced antenna drift technique mode needs to have a large aperture antenna array in order to get the narrow pencil beam is required for wind speed and direction accuracy. To meet the above requirements a microstrip patch antenna single element is used to design a 2, 4, 8 & 16-element linear antenna array for Tropospheric Wind Profiling Radar Operating at 0.43GHz. Conception details and simulation results are also given for the both single element & 16-element linear antenna array. The designed and simulated results are presented. A full wave electromagnetic simulator zeland IE3D V12.02 is used to validate the design approach. The simulated results below present are valid over the 0.43GHz band and the simulated parameters contains the VSWR, Return loss, impedance, gain, directivity, efficiency and elevation gain patterns.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134066026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306270
Xiongjun Fu, Chengyan Zhang, Guangjun Cheng, M. Xie
Inverse Synthetic Aperture Radar (ISAR) has the function of remote imaging with non-cooperative targets. It has important value in application of the space target surveillance, recognition and cataloging, and satellite fault diagnosis. This paper describes multi-dimensional ISAR imaging technology in detail. Research results of real-time ISAR imaging with mono-static and multi-polarization, and bi-static ISAR imaging are presented. This paper also shows the development trends of ISAR imaging technology.
{"title":"ISAR imaging applications for orbital objects","authors":"Xiongjun Fu, Chengyan Zhang, Guangjun Cheng, M. Xie","doi":"10.1109/APSAR.2015.7306270","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306270","url":null,"abstract":"Inverse Synthetic Aperture Radar (ISAR) has the function of remote imaging with non-cooperative targets. It has important value in application of the space target surveillance, recognition and cataloging, and satellite fault diagnosis. This paper describes multi-dimensional ISAR imaging technology in detail. Research results of real-time ISAR imaging with mono-static and multi-polarization, and bi-static ISAR imaging are presented. This paper also shows the development trends of ISAR imaging technology.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123728231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306153
Byungjoon Kim, Duksoo Kim, Youngjoon Lim, Sangwook Nam, Eun-Hyuk Kwak, Boo‐Gyoun Kim, H. Yeo, Jaeha Kim
In this paper, a dual-band, frequency-modulated continuous-wave (FMCW) radar for short-range through-wall detection is proposed and implemented. This radar adopts a shared-aperture antenna technique for reducing antenna area and high-speed chirping to avoid flicker noise. It operates at the S-band (3 GHz) and the X-band (9 GHz), with 486 MHz chirp bandwidth and 860 MHz chirp bandwidth, respectively. The chirp rates are 11,050 GHz/s and 22,000 GHz/s at the S- and X-bands, respectively. The radar has successfully detected a target through a wooden wall.
{"title":"A dual-band FMCW radar for through-wall detection","authors":"Byungjoon Kim, Duksoo Kim, Youngjoon Lim, Sangwook Nam, Eun-Hyuk Kwak, Boo‐Gyoun Kim, H. Yeo, Jaeha Kim","doi":"10.1109/APSAR.2015.7306153","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306153","url":null,"abstract":"In this paper, a dual-band, frequency-modulated continuous-wave (FMCW) radar for short-range through-wall detection is proposed and implemented. This radar adopts a shared-aperture antenna technique for reducing antenna area and high-speed chirping to avoid flicker noise. It operates at the S-band (3 GHz) and the X-band (9 GHz), with 486 MHz chirp bandwidth and 860 MHz chirp bandwidth, respectively. The chirp rates are 11,050 GHz/s and 22,000 GHz/s at the S- and X-bands, respectively. The radar has successfully detected a target through a wooden wall.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123563946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306219
Mingzhe Zhang, Chao Wang, Hong Zhang, Meng Liu, Lei Xie
Traditional pixel-based change detection methods are undertaken using the pixel as the research unit. These methods may give high false alarm rate and broken areas, because they don't use semantic information. In order to solve this problem, we present a novel change detection method which is based on radon transform and super-pixel segmentation. First, radon transform is used to achieve a stable difference map, and the Otsu algorithm is used to gain the initial change mask. Second, in order to reduce false alarm rate and preserve edges between changed class and unchanged class, the simple linear iterative clustering(SLIC) super-pixel segmentation is introduced into SAR image segmentation. Then, the spatial-based change detection scheme is utilized for the fusion of initial change mask and segmentation result. Two radarsat-2 images of Suzhou, China, acquired on April 9,2009 and June 15, 2010 are used for our experiment. Experiment results show that the proposed method is effective for SAR image change detection in terms of edge preservation and change detection rate.
{"title":"A novel SAR change detection based on radon transform and super-pixel segmentation","authors":"Mingzhe Zhang, Chao Wang, Hong Zhang, Meng Liu, Lei Xie","doi":"10.1109/APSAR.2015.7306219","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306219","url":null,"abstract":"Traditional pixel-based change detection methods are undertaken using the pixel as the research unit. These methods may give high false alarm rate and broken areas, because they don't use semantic information. In order to solve this problem, we present a novel change detection method which is based on radon transform and super-pixel segmentation. First, radon transform is used to achieve a stable difference map, and the Otsu algorithm is used to gain the initial change mask. Second, in order to reduce false alarm rate and preserve edges between changed class and unchanged class, the simple linear iterative clustering(SLIC) super-pixel segmentation is introduced into SAR image segmentation. Then, the spatial-based change detection scheme is utilized for the fusion of initial change mask and segmentation result. Two radarsat-2 images of Suzhou, China, acquired on April 9,2009 and June 15, 2010 are used for our experiment. Experiment results show that the proposed method is effective for SAR image change detection in terms of edge preservation and change detection rate.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123659557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306263
Aire Olesk, K. Voormansik, Mirjam Pohjala, M. Noorma
This research presents the performance of the recently launched C-band Sentinel-1 and L-band ALOS-2 satellite missions for detecting forest clear-cuts and thinning in the winter season in coniferous and deciduous forests within Estonia. SAR data were acquired from September 2014 to April 2015 to analyze the cross-polarized backscatter dynamics over 76 stands before and after the logging event. Both clear-cuts and thinning treatments were considered with stand size ranging from 0.11-6.44 ha and compared to the in situ reference data. The results show that the accuracy of logging detection is influenced by the weather conditions as well as the size of the stand. Both Sentinel-1 and ALOS-2 provide reliable forest clear-cut monitoring and are suitable for an operational change detection service for forest stands larger than 0.5 ha.
{"title":"Forest change detection from Sentinel-1 and ALOS-2 satellite images","authors":"Aire Olesk, K. Voormansik, Mirjam Pohjala, M. Noorma","doi":"10.1109/APSAR.2015.7306263","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306263","url":null,"abstract":"This research presents the performance of the recently launched C-band Sentinel-1 and L-band ALOS-2 satellite missions for detecting forest clear-cuts and thinning in the winter season in coniferous and deciduous forests within Estonia. SAR data were acquired from September 2014 to April 2015 to analyze the cross-polarized backscatter dynamics over 76 stands before and after the logging event. Both clear-cuts and thinning treatments were considered with stand size ranging from 0.11-6.44 ha and compared to the in situ reference data. The results show that the accuracy of logging detection is influenced by the weather conditions as well as the size of the stand. Both Sentinel-1 and ALOS-2 provide reliable forest clear-cut monitoring and are suitable for an operational change detection service for forest stands larger than 0.5 ha.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"239 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124634546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306144
Lu Junqi, Guo Yongxin
A novel aperiodic phased array for space-borne synthetic aperture Radar (SAR) is presented which has fewer active chains than a corresponding periodic phased array while maintains comparable radiation performance. The design of proposed aperiodic phased array is based on equal amplitude sparse array. Compare to other aperiodic sparse phased array antennas for space-borne SAR which have been reported before, in the design of proposed sparse array a novel `active-passive array' technology is utilized to modify the equivalent aperture current distribution, therefore the radiation performance can be improved significantly in terms of gain and sidelobe level. Simulation results show that the proposed phased array possess similar radiation performance to a periodic array while reduces the active chains number to 75%. Simplified evaluation of SAR Ambiguity-to-Signal Ratio also show that the proposed array exhibits similar performance of traditional periodic array, which is obviously better than that of conventional aperiodic sparse array. The design principle of `active-passive array' as well as associated array synthesis method are also discussed.
{"title":"Novel aperiodic phased array with reduced number of active chains for space-borne SAR","authors":"Lu Junqi, Guo Yongxin","doi":"10.1109/APSAR.2015.7306144","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306144","url":null,"abstract":"A novel aperiodic phased array for space-borne synthetic aperture Radar (SAR) is presented which has fewer active chains than a corresponding periodic phased array while maintains comparable radiation performance. The design of proposed aperiodic phased array is based on equal amplitude sparse array. Compare to other aperiodic sparse phased array antennas for space-borne SAR which have been reported before, in the design of proposed sparse array a novel `active-passive array' technology is utilized to modify the equivalent aperture current distribution, therefore the radiation performance can be improved significantly in terms of gain and sidelobe level. Simulation results show that the proposed phased array possess similar radiation performance to a periodic array while reduces the active chains number to 75%. Simplified evaluation of SAR Ambiguity-to-Signal Ratio also show that the proposed array exhibits similar performance of traditional periodic array, which is obviously better than that of conventional aperiodic sparse array. The design principle of `active-passive array' as well as associated array synthesis method are also discussed.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"195 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116697711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-10-29DOI: 10.1109/APSAR.2015.7306313
Xiaoran Shi, Feng Zhou, Sheng Jin, Zi-jing Zhang, Lei Liu
Extraction of features and subsequent classification of ground moving targets, especially humans and vehicles, are topics of great relevance for the theoretical research and practical application in the signal processing of the ground surveillance radar. Based on time-frequency (TF) spectrograms, a novel method for the feature extraction of micro-motion targets is proposed in this paper. The experimental results under different signal-to-noise ratio (SNR) and training sample number conditions verify the validity and robustness of the proposed method.
{"title":"Textural feature extraction and classification for humans and vehicles","authors":"Xiaoran Shi, Feng Zhou, Sheng Jin, Zi-jing Zhang, Lei Liu","doi":"10.1109/APSAR.2015.7306313","DOIUrl":"https://doi.org/10.1109/APSAR.2015.7306313","url":null,"abstract":"Extraction of features and subsequent classification of ground moving targets, especially humans and vehicles, are topics of great relevance for the theoretical research and practical application in the signal processing of the ground surveillance radar. Based on time-frequency (TF) spectrograms, a novel method for the feature extraction of micro-motion targets is proposed in this paper. The experimental results under different signal-to-noise ratio (SNR) and training sample number conditions verify the validity and robustness of the proposed method.","PeriodicalId":350698,"journal":{"name":"2015 IEEE 5th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117123511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：