X-ray computed tomography(CT)has been an important technology in paleontology for several decades.It helps researchers to acquire detailed anatomical structures of fossils non-destructively.Despite its widespread appl...X-ray computed tomography(CT)has been an important technology in paleontology for several decades.It helps researchers to acquire detailed anatomical structures of fossils non-destructively.Despite its widespread application,developing an efficient and user-friendly method for segmenting CT data continues to be a formidable challenge in the field.Most CT data segmentation software operates on 2D interfaces,which limits flexibility for real-time adjustments in 3D segmentation.Here,we introduce Curves Mode in Drishti Paint 3.2,an open-source tool for CT data segmentation.Drishti Paint 3.2 allows users to manually or semi-automatically segment the CT data in both 2D and 3D environments,providing a novel solution for revisualizing CT data in paleontological studies.展开更多
Three-dimensional(3D) synthetic aperture radar(SAR)extends the conventional 2D images into 3D features by several acquisitions in different aspects. Compared with 3D techniques via multiple observations in elevation, ...Three-dimensional(3D) synthetic aperture radar(SAR)extends the conventional 2D images into 3D features by several acquisitions in different aspects. Compared with 3D techniques via multiple observations in elevation, e.g. SAR interferometry(InSAR) and SAR tomography(TomoSAR), holographic SAR can retrieve 3D structure by observations in azimuth. This paper focuses on designing a novel type of orbit to achieve SAR regional all-azimuth observation(AAO) for embedded targets detection and holographic 3D reconstruction. The ground tracks of the AAO orbit separate the earth surface into grids. Target in these grids can be accessed with an azimuth angle span of360°, which is similar to the flight path of airborne circular SAR(CSAR). Inspired from the successive coverage orbits of optical sensors, several optimizations are made in the proposed method to ensure favorable grazing angles, the performance of 3D reconstruction, and long-term supervision for SAR sensors. Simulation experiments show the regional AAO can be completed within five hours. In addition, a second AAO of the same area can be duplicated in two days. Finally, an airborne SAR data process result is presented to illustrate the significance of AAO in 3D reconstruction.展开更多
A 3D motion and geometric information system of single-antenna radar is proposed,which can be supported by spotlight synthetic aperture radar（SAR） system and inverse SAR（ISAR） system involving relative 3D motion o...A 3D motion and geometric information system of single-antenna radar is proposed,which can be supported by spotlight synthetic aperture radar（SAR） system and inverse SAR（ISAR） system involving relative 3D motion of the rigid target.In this system,applying the geometry invariance of the rigid target,the unknown 3D shape and motion of the radar target can be reconstructed from the 1D range data of some scatterers extracted from the high-resolution range image.Compared with the current 1D-to-3D algorithm,in the proposed algorithm,the requirement of the 1D range data is expanded to incomplete formation involving large angular motion of the target and hence,the quantity of the scatterers and the abundance of 3D motion are enriched.Furthermore,with the three selected affine coordinates fixed,the multi-solution problem of the reconstruction is solved and the technique of nonlinear optimization can be successfully utilized in the system.Two simulations are implemented which verify the higher robustness of the system and the better performance of the 3D reconstruction for the radar target with unknown relative motion.展开更多
In this study,the morphology and ultrastructure of the compound eye of L.lewisii were investigated using scanning electron microscopy(SEM),transmission electron microscopy(TEM),microcomputed tomography(μCT),and 3D re...In this study,the morphology and ultrastructure of the compound eye of L.lewisii were investigated using scanning electron microscopy(SEM),transmission electron microscopy(TEM),microcomputed tomography(μCT),and 3D reconstruction.The compound eye of L.lewisii was of the apposition type,with an average of 121.88±7.64 ommatidia in males and 119.00±4.71 ommatidia in females.Each ommatidium was composed of a biconvex cornea,an acone consisting of four cone cells,eight retinular cells along with the rhabdom,two primary pigment cells,and numerous secondary pigment cells.The open type of rhabdom in L.lewisii consists of six peripheral rhabdomeres contributed by the six peripheral retinular cells(R1~R6)and two vertically attached central rhabdomeres contributed by R7 and R8 respectively.The orientation of microvilli suggested a weak sensitivity to polarized light perception.展开更多
The Tyrannosauridae,which is characterized by specialized pachydont dentition and putative bone-cracking predatory strategies,is one of the most extensively studied theropod lineages.Although tooth replacement pattern...The Tyrannosauridae,which is characterized by specialized pachydont dentition and putative bone-cracking predatory strategies,is one of the most extensively studied theropod lineages.Although tooth replacement patterns,crucial for understanding feeding behaviors,have been thoroughly studied in this group,studies on non-tyrannosaurid tyrannosauroids are relatively scarce.This study utilizes high-resolution CT data to investigate the tooth replacement pattern in two specimens of Guanlong wucaii,a Late Jurassic tyrannosauroid,and provides insights into the evolution of tooth replacement across Tyrannosauroidea.Second-generation replacement teeth,a rarity observed mainly in giant predatory theropods(e.g.some tyrannosaurids),were detected in the dentary dentition of the juvenile Guanlong.Zahnreihen reconstructions display a consistent cephalad alternating tooth replacement pattern in the maxilla and the dentary of both of the examined individuals,with Z-spacing values exceeding 2.0.As Guanlong grows,the Z-spacing value in the maxillary dentition increases,resembling the ontogenetic changes documented in the Tyrannosauridae.Additionally,like Tarbosaurus,Guanlong also displays a discontinuity between the tooth replacement waves at the premaxilla-maxilla boundary.This study thus demonstrates that some tyrannosaurid-like tooth replacement patterns were acquired before the origin of the Tyrannosauridae.展开更多
Three-dimensional(3D)reconstruction based on aerial images has broad prospects,and feature matching is an important step of it.However,for high-resolution aerial images,there are usually problems such as long time,mis...Three-dimensional(3D)reconstruction based on aerial images has broad prospects,and feature matching is an important step of it.However,for high-resolution aerial images,there are usually problems such as long time,mismatching and sparse feature pairs using traditional algorithms.Therefore,an algorithm is proposed to realize fast,accurate and dense feature matching.The algorithm consists of four steps.Firstly,we achieve a balance between the feature matching time and the number of matching pairs by appropriately reducing the image resolution.Secondly,to realize further screening of the mismatches,a feature screening algorithm based on similarity judgment or local optimization is proposed.Thirdly,to make the algorithm more widely applicable,we combine the results of different algorithms to get dense results.Finally,all matching feature pairs in the low-resolution images are restored to the original images.Comparisons between the original algorithms and our algorithm show that the proposed algorithm can effectively reduce the matching time,screen out the mismatches,and improve the number of matches.展开更多
文摘X-ray computed tomography(CT)has been an important technology in paleontology for several decades.It helps researchers to acquire detailed anatomical structures of fossils non-destructively.Despite its widespread application,developing an efficient and user-friendly method for segmenting CT data continues to be a formidable challenge in the field.Most CT data segmentation software operates on 2D interfaces,which limits flexibility for real-time adjustments in 3D segmentation.Here,we introduce Curves Mode in Drishti Paint 3.2,an open-source tool for CT data segmentation.Drishti Paint 3.2 allows users to manually or semi-automatically segment the CT data in both 2D and 3D environments,providing a novel solution for revisualizing CT data in paleontological studies.
基金supported by the National Natural Science Foundation of China (62001436)the Natural Science Foundation of Jiangsu Province under (BK 20190143,JSGG20190823094603691)。
文摘Three-dimensional(3D) synthetic aperture radar(SAR)extends the conventional 2D images into 3D features by several acquisitions in different aspects. Compared with 3D techniques via multiple observations in elevation, e.g. SAR interferometry(InSAR) and SAR tomography(TomoSAR), holographic SAR can retrieve 3D structure by observations in azimuth. This paper focuses on designing a novel type of orbit to achieve SAR regional all-azimuth observation(AAO) for embedded targets detection and holographic 3D reconstruction. The ground tracks of the AAO orbit separate the earth surface into grids. Target in these grids can be accessed with an azimuth angle span of360°, which is similar to the flight path of airborne circular SAR(CSAR). Inspired from the successive coverage orbits of optical sensors, several optimizations are made in the proposed method to ensure favorable grazing angles, the performance of 3D reconstruction, and long-term supervision for SAR sensors. Simulation experiments show the regional AAO can be completed within five hours. In addition, a second AAO of the same area can be duplicated in two days. Finally, an airborne SAR data process result is presented to illustrate the significance of AAO in 3D reconstruction.
基金supported by the National Natural Science Foundation of China (60572093)the Doctoral Program of Higher Education(20050004016)the Outstanding Doctoral Science Innovation Foundation of Beijing Jiaotong University (141095522)
文摘A 3D motion and geometric information system of single-antenna radar is proposed,which can be supported by spotlight synthetic aperture radar（SAR） system and inverse SAR（ISAR） system involving relative 3D motion of the rigid target.In this system,applying the geometry invariance of the rigid target,the unknown 3D shape and motion of the radar target can be reconstructed from the 1D range data of some scatterers extracted from the high-resolution range image.Compared with the current 1D-to-3D algorithm,in the proposed algorithm,the requirement of the 1D range data is expanded to incomplete formation involving large angular motion of the target and hence,the quantity of the scatterers and the abundance of 3D motion are enriched.Furthermore,with the three selected affine coordinates fixed,the multi-solution problem of the reconstruction is solved and the technique of nonlinear optimization can be successfully utilized in the system.Two simulations are implemented which verify the higher robustness of the system and the better performance of the 3D reconstruction for the radar target with unknown relative motion.
文摘In this study,the morphology and ultrastructure of the compound eye of L.lewisii were investigated using scanning electron microscopy(SEM),transmission electron microscopy(TEM),microcomputed tomography(μCT),and 3D reconstruction.The compound eye of L.lewisii was of the apposition type,with an average of 121.88±7.64 ommatidia in males and 119.00±4.71 ommatidia in females.Each ommatidium was composed of a biconvex cornea,an acone consisting of four cone cells,eight retinular cells along with the rhabdom,two primary pigment cells,and numerous secondary pigment cells.The open type of rhabdom in L.lewisii consists of six peripheral rhabdomeres contributed by the six peripheral retinular cells(R1~R6)and two vertically attached central rhabdomeres contributed by R7 and R8 respectively.The orientation of microvilli suggested a weak sensitivity to polarized light perception.
文摘The Tyrannosauridae,which is characterized by specialized pachydont dentition and putative bone-cracking predatory strategies,is one of the most extensively studied theropod lineages.Although tooth replacement patterns,crucial for understanding feeding behaviors,have been thoroughly studied in this group,studies on non-tyrannosaurid tyrannosauroids are relatively scarce.This study utilizes high-resolution CT data to investigate the tooth replacement pattern in two specimens of Guanlong wucaii,a Late Jurassic tyrannosauroid,and provides insights into the evolution of tooth replacement across Tyrannosauroidea.Second-generation replacement teeth,a rarity observed mainly in giant predatory theropods(e.g.some tyrannosaurids),were detected in the dentary dentition of the juvenile Guanlong.Zahnreihen reconstructions display a consistent cephalad alternating tooth replacement pattern in the maxilla and the dentary of both of the examined individuals,with Z-spacing values exceeding 2.0.As Guanlong grows,the Z-spacing value in the maxillary dentition increases,resembling the ontogenetic changes documented in the Tyrannosauridae.Additionally,like Tarbosaurus,Guanlong also displays a discontinuity between the tooth replacement waves at the premaxilla-maxilla boundary.This study thus demonstrates that some tyrannosaurid-like tooth replacement patterns were acquired before the origin of the Tyrannosauridae.
基金This work was supported by the Equipment Pre-Research Foundation of China(6140001020310).
文摘Three-dimensional(3D)reconstruction based on aerial images has broad prospects,and feature matching is an important step of it.However,for high-resolution aerial images,there are usually problems such as long time,mismatching and sparse feature pairs using traditional algorithms.Therefore,an algorithm is proposed to realize fast,accurate and dense feature matching.The algorithm consists of four steps.Firstly,we achieve a balance between the feature matching time and the number of matching pairs by appropriately reducing the image resolution.Secondly,to realize further screening of the mismatches,a feature screening algorithm based on similarity judgment or local optimization is proposed.Thirdly,to make the algorithm more widely applicable,we combine the results of different algorithms to get dense results.Finally,all matching feature pairs in the low-resolution images are restored to the original images.Comparisons between the original algorithms and our algorithm show that the proposed algorithm can effectively reduce the matching time,screen out the mismatches,and improve the number of matches.
