This paper presents a Doppler passive location method for moving targets with fixed single station using the Doppler frequency shift and time difference information.First,based on the relationship between frequency sh...This paper presents a Doppler passive location method for moving targets with fixed single station using the Doppler frequency shift and time difference information.First,based on the relationship between frequency shift and path difference,the virtual path difference is calculated from the measured value of Doppler frequency shift by means of mean value correction.Then,under the assumption that the target is moving at a constant speed along a straight line,two coaxial virtual double base arrays are constructed by using the moving track of the moving target based on the method of fixed period time difference.On this basis,the moving distance of the moving target can be calculated by using the ratio relationship between the frequency difference and the radial distance between the two adjacent detection points in the middle of the array,and the linear solution of the two double base path difference positioning equations.At this point,the relative coordinate position of the moving target can be obtained by directly using the linear solution of the double base path difference positioning equation again.展开更多
Non-uniform linear array(NULA)configurations are well renowned due to their structural ability for providing increased degrees of freedom(DOF)and wider array aperture than uniform linear arrays(ULAs).These characteris...Non-uniform linear array(NULA)configurations are well renowned due to their structural ability for providing increased degrees of freedom(DOF)and wider array aperture than uniform linear arrays(ULAs).These characteristics play a significant role in improving the direction-of-arrival(DOA)estimation accuracy.However,most of the existing NULA geometries are primarily applicable to circular sources(CSs),while they limitedly improve the DOF and continuous virtual aperture for noncircular sources(NCSs).Toward this purpose,we present a triaddisplaced ULAs(Tdis-ULAs)configuration for NCS.The TdisULAs structure generally consists of three ULAs,which are appropriately placed.The proposed antenna array approach fully exploits the non-circular characteristics of the sources.Given the same number of elements,the Tdis-ULAs design achieves more DOF and larger hole-free co-array aperture than its sparse array competitors.Advantageously,the number of uniform DOF,optimal distribution of elements among the ULAs,and precise element positions are uniquely determined by the closed-form expressions.Moreover,the proposed array also produces a filled resulting co-array.Numerical simulations are conducted to show the performance advantages of the proposed Tdis-ULAs configuration over its counterpart designs.展开更多
Virtual reality(VR)has been a promising tool for developing visuospatial tasks.Among visuospatial tasks,mental rotation tasks are widely used in the assessment of visuospatial ability.Males have a distinct advantage i...Virtual reality(VR)has been a promising tool for developing visuospatial tasks.Among visuospatial tasks,mental rotation tasks are widely used in the assessment of visuospatial ability.Males have a distinct advantage in mental rotation ability compared to females,yet it is generally produced by investigations based on two-dimensional(2D)images on a computer screen.Sex differences in mental rotation tasks with three-dimensional(3D)objects in VR were not fully investigated.It is unclear whether the male's advantages in 2D mental rotation tasks are weakened in 3D tasks.The aim of this study was to provide new insights into the understanding of sex differences in mental rotation tasks presented in VR.Here,we developed a VR mental rotation task(VR-MRT)using 3D objects presented by a head-mounted display(HMD)and used VR-based eye tracking and electroencephalography(EEG)to examine eye movements and neural oscillations for males and females.Our results showed that females preferred a piecemeal strategy compared to males,suggesting a significant sex difference in visual strategy.More importantly,we found no significant sex differences in alpha-band and beta-band oscillations related to rotation processes of VR-MRT.These findings indicated that sex differences in the VR-MRT were mainly attributed to the selection of visual strategy rather than the rotation processes.The study helps to comprehensively understand the dominant factors contributing to the sex differences in the VR-MRT.展开更多
文摘This paper presents a Doppler passive location method for moving targets with fixed single station using the Doppler frequency shift and time difference information.First,based on the relationship between frequency shift and path difference,the virtual path difference is calculated from the measured value of Doppler frequency shift by means of mean value correction.Then,under the assumption that the target is moving at a constant speed along a straight line,two coaxial virtual double base arrays are constructed by using the moving track of the moving target based on the method of fixed period time difference.On this basis,the moving distance of the moving target can be calculated by using the ratio relationship between the frequency difference and the radial distance between the two adjacent detection points in the middle of the array,and the linear solution of the two double base path difference positioning equations.At this point,the relative coordinate position of the moving target can be obtained by directly using the linear solution of the double base path difference positioning equation again.
基金supported by the National Natural Science Foundation of China(62031017,61971221)the Fundamental Research Funds for the Central Universities of China(NP2020104)。
文摘Non-uniform linear array(NULA)configurations are well renowned due to their structural ability for providing increased degrees of freedom(DOF)and wider array aperture than uniform linear arrays(ULAs).These characteristics play a significant role in improving the direction-of-arrival(DOA)estimation accuracy.However,most of the existing NULA geometries are primarily applicable to circular sources(CSs),while they limitedly improve the DOF and continuous virtual aperture for noncircular sources(NCSs).Toward this purpose,we present a triaddisplaced ULAs(Tdis-ULAs)configuration for NCS.The TdisULAs structure generally consists of three ULAs,which are appropriately placed.The proposed antenna array approach fully exploits the non-circular characteristics of the sources.Given the same number of elements,the Tdis-ULAs design achieves more DOF and larger hole-free co-array aperture than its sparse array competitors.Advantageously,the number of uniform DOF,optimal distribution of elements among the ULAs,and precise element positions are uniquely determined by the closed-form expressions.Moreover,the proposed array also produces a filled resulting co-array.Numerical simulations are conducted to show the performance advantages of the proposed Tdis-ULAs configuration over its counterpart designs.
基金This work was supported by the National Nature Science Foundation of China(11972066,T2288101,U20A20390,11827803)the National Key Research and Development Plan of China(2020YFC2005902).
文摘Virtual reality(VR)has been a promising tool for developing visuospatial tasks.Among visuospatial tasks,mental rotation tasks are widely used in the assessment of visuospatial ability.Males have a distinct advantage in mental rotation ability compared to females,yet it is generally produced by investigations based on two-dimensional(2D)images on a computer screen.Sex differences in mental rotation tasks with three-dimensional(3D)objects in VR were not fully investigated.It is unclear whether the male's advantages in 2D mental rotation tasks are weakened in 3D tasks.The aim of this study was to provide new insights into the understanding of sex differences in mental rotation tasks presented in VR.Here,we developed a VR mental rotation task(VR-MRT)using 3D objects presented by a head-mounted display(HMD)and used VR-based eye tracking and electroencephalography(EEG)to examine eye movements and neural oscillations for males and females.Our results showed that females preferred a piecemeal strategy compared to males,suggesting a significant sex difference in visual strategy.More importantly,we found no significant sex differences in alpha-band and beta-band oscillations related to rotation processes of VR-MRT.These findings indicated that sex differences in the VR-MRT were mainly attributed to the selection of visual strategy rather than the rotation processes.The study helps to comprehensively understand the dominant factors contributing to the sex differences in the VR-MRT.
