利用微波在对流层的散射现象进行电磁侦测是实现超视距雷达辐射源探测的有效手段之一.随着探测威力、分辨力要求的提高,对于散射多径引起的衰落相关导致接收协方差矩阵秩亏损,令多重信号分类(multiple signal classification,MUSIC)等...利用微波在对流层的散射现象进行电磁侦测是实现超视距雷达辐射源探测的有效手段之一.随着探测威力、分辨力要求的提高,对于散射多径引起的衰落相关导致接收协方差矩阵秩亏损,令多重信号分类(multiple signal classification,MUSIC)等基于特征分解的超分辨类测向算法失效,以及散射机制下大型分布式源产生的相位扩散导致接收阵列流形失配等问题,文章根据近期建立的散射衰落相关模型设计相互独立的多波束排布,并相应地提出一种修正的线性约束最小方差(linearly constrained minimum variance,LCMV)方法补偿相位扩散影响,将接收信号由受衰落相关影响的阵元域变换到独立的波束域,并在波束域进行超分辨测向.仿真结果验证了测向算法在散射多径衰落条件下的有效性,对600km目标散射信号积累300快拍能达到0.5°的估角精度.展开更多
The isothermal section of Ag-Ti-Zr ternary system at 1023 K was determined by diffusion triple and electron probe microanalysis. The results indicate that four binary intermetallic phases of AgTi, AgTi2, AgZr and AgZr...The isothermal section of Ag-Ti-Zr ternary system at 1023 K was determined by diffusion triple and electron probe microanalysis. The results indicate that four binary intermetallic phases of AgTi, AgTi2, AgZr and AgZr2 are found in Ag-Ti-Zr ternary system at 1 023 K. AgZr2 and AgTi2 form a continuous solid solution, namely Ag(Ti,Zr)2. Four three-phase regions: AgTi +AgZr + Ag, AgTi +AgZr + Ag (Ti, Zr)2, α-Zr +β(Ti, Zr) + Ag (Ti, Zr) 2 and α-Ti +β(Ti, Zr) + Ag (Ti, Zr)2 exist in the isothermal section. No ternary compound is observed.展开更多
In ground-based astronomy, images of objects in outer space are acquired via ground-based tele- scopes. However, the imaging system is generally interfered by atmospheric turbulence and hence images so acquired are bl...In ground-based astronomy, images of objects in outer space are acquired via ground-based tele- scopes. However, the imaging system is generally interfered by atmospheric turbulence and hence images so acquired are blurred with unknown point spread function （PSF）. To restore the observed images, aberration of the wavefront at the telescope＇s aperture, i.e., the phase, is utilized to derive the PSF. However, the phase is not readily available. Instead, its gradients can be collected by wavefront sensors. Thus the usual approach is to use regularization methods to reconstruct high-resolution phase gradients and then use them to recover the phase in high accuracy. Here, we develop a model that reconstructs the phase directly. The proposed model uses the tight frame regularization and it can be solved efficiently by the Douglas-Rachford alternating direction method of multipliers whose convergence has been well established. Numerical results illustrate that our new model is efficient and gives more accurate estimation for the PSF.展开更多
基金supported by the Project of Science Research from Education Department of Anhui Province(KJ2009B102)the Fund for Excellent Young talents in the Higher Education Institutions of Anhui Province(2009SQRZ087)~~
基金Projects(50371104 50401011) supported by the National Natural Science Foundation of China
文摘The isothermal section of Ag-Ti-Zr ternary system at 1023 K was determined by diffusion triple and electron probe microanalysis. The results indicate that four binary intermetallic phases of AgTi, AgTi2, AgZr and AgZr2 are found in Ag-Ti-Zr ternary system at 1 023 K. AgZr2 and AgTi2 form a continuous solid solution, namely Ag(Ti,Zr)2. Four three-phase regions: AgTi +AgZr + Ag, AgTi +AgZr + Ag (Ti, Zr)2, α-Zr +β(Ti, Zr) + Ag (Ti, Zr) 2 and α-Ti +β(Ti, Zr) + Ag (Ti, Zr)2 exist in the isothermal section. No ternary compound is observed.
基金supported by Hong Kong Research Grants Council(HKRGC)(Grant Nos.CUHK400412 and HKBU203311)CUHK Direct Allocation Grant(Grant No.4053007)+1 种基金CUHK Focused Investment Scheme(Grant No.1902036)National Natural Science Foundation of China(Grant No.11301055)
文摘In ground-based astronomy, images of objects in outer space are acquired via ground-based tele- scopes. However, the imaging system is generally interfered by atmospheric turbulence and hence images so acquired are blurred with unknown point spread function （PSF）. To restore the observed images, aberration of the wavefront at the telescope＇s aperture, i.e., the phase, is utilized to derive the PSF. However, the phase is not readily available. Instead, its gradients can be collected by wavefront sensors. Thus the usual approach is to use regularization methods to reconstruct high-resolution phase gradients and then use them to recover the phase in high accuracy. Here, we develop a model that reconstructs the phase directly. The proposed model uses the tight frame regularization and it can be solved efficiently by the Douglas-Rachford alternating direction method of multipliers whose convergence has been well established. Numerical results illustrate that our new model is efficient and gives more accurate estimation for the PSF.
