In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inver...In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inverse scattering problems by Tikhonov regularization method.展开更多
This paper is concerned with the properties of propagation fax-field patterns corresponding to the scattering of time harmonic acoustic waves by a bounded penetrable obstacle in an ocean waveguide. The sets of solutio...This paper is concerned with the properties of propagation fax-field patterns corresponding to the scattering of time harmonic acoustic waves by a bounded penetrable obstacle in an ocean waveguide. The sets of solutions to the transmission problem are constructed such that the restriction of these solutions to the boundary of the penetrable obstacle is dense in a Hilbert space. Then conditions under which a set of propagation far-field patterns is complete in a Hilbert space are determined. These properties are important in investigating inverse transmission problems in an ocean waveguide.展开更多
We study the inverse problem of recovering the scatterer shape from the far-field pattern(FFP)in the presence of noise.Furthermore,only a discrete partial aperture is usually known.This problem is ill-posed and is fre...We study the inverse problem of recovering the scatterer shape from the far-field pattern(FFP)in the presence of noise.Furthermore,only a discrete partial aperture is usually known.This problem is ill-posed and is frequently addressed using regularization.Instead,we propose to use a direct approach denoising the FFP using a filtering technique.The effectiveness of the technique is studied on a scatterer with the shape of the ellipse with a tower.The forward scattering problem is solved using the finite element method(FEM).The numerical FFP is additionally corrupted by Gaussian noise.The shape parameters are found based on a least-square error estimator.If eu¥is a perturbation of the FFP then we attempt to find G,the scatterer shape,which minimizes k u¥−eu¥k using the conjugate gradient method for the denoised FFP.展开更多
c-plane GaN-based blue laser diodes（LDs） were fabricated with Al-free cladding layers（CLs） and deepened etching depth of mesa structure, so the aspect ratio of the far-field pattern（FFP） of the laser beam can be...c-plane GaN-based blue laser diodes（LDs） were fabricated with Al-free cladding layers（CLs） and deepened etching depth of mesa structure, so the aspect ratio of the far-field pattern（FFP） of the laser beam can be reduced to as low as 1.7, which is nearly the same as conventional AlGa In P-based red LDs. By using GaN CLs,the radiation angle of the laser beam θ⊥ is only 10.1° in the direction perpendicular to the junction plane. After forming a deeply etched mesa, the beam divergence angle parallel to the junction plane of FFP, θ;, increases from4.9° to 5.8°. After using the modified structure, the operation voltage of LD is effectively reduced by 2 V at an injection current of 50 mA, but the threshold current value increases. The etching damage may be one of the main reasons responsible for the increase of the threshold current.展开更多
针对大型分块反射面天线面板调整次数多、效率低的问题,提出了一种从天线远场方向图反推出面板调整量进而快速调整的方法。应用物理光学(physical optics,PO)法建立了表面节点位移与远区电场的线性关系,将面板调整向量与远区辐射场强用...针对大型分块反射面天线面板调整次数多、效率低的问题,提出了一种从天线远场方向图反推出面板调整量进而快速调整的方法。应用物理光学(physical optics,PO)法建立了表面节点位移与远区电场的线性关系,将面板调整向量与远区辐射场强用线性方程组联系起来。利用奇异值分解(singular value decomposition,SVD)法求解线性方程组得调整向量,从而实现由方向图反推调整量的目的。对某工程案例进行了分析计算,给出了相应的数据与曲线,证明了所提方法的有效性,为大型天线反射面板的精确调整提供了指导。展开更多
基金Shanghai Youth Science FoundationSupported in Part by Shanghai ScienceTechnology Development Foundation
文摘In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inverse scattering problems by Tikhonov regularization method.
基金Project supported by the National Natural Science Foundation of China (No.10672128)the Doctor Foundation of Wuhan University of Technology (No.471-38650238)the Undergraduate Innovative Foundation of Wuhan University of Technology (No.A145)
文摘This paper is concerned with the properties of propagation fax-field patterns corresponding to the scattering of time harmonic acoustic waves by a bounded penetrable obstacle in an ocean waveguide. The sets of solutions to the transmission problem are constructed such that the restriction of these solutions to the boundary of the penetrable obstacle is dense in a Hilbert space. Then conditions under which a set of propagation far-field patterns is complete in a Hilbert space are determined. These properties are important in investigating inverse transmission problems in an ocean waveguide.
文摘We study the inverse problem of recovering the scatterer shape from the far-field pattern(FFP)in the presence of noise.Furthermore,only a discrete partial aperture is usually known.This problem is ill-posed and is frequently addressed using regularization.Instead,we propose to use a direct approach denoising the FFP using a filtering technique.The effectiveness of the technique is studied on a scatterer with the shape of the ellipse with a tower.The forward scattering problem is solved using the finite element method(FEM).The numerical FFP is additionally corrupted by Gaussian noise.The shape parameters are found based on a least-square error estimator.If eu¥is a perturbation of the FFP then we attempt to find G,the scatterer shape,which minimizes k u¥−eu¥k using the conjugate gradient method for the denoised FFP.
基金supported by the National Key R&D Program(Nos.2017YFB0403100,2017YFB0403101)the National Natural Science Foundation of China(Nos.61534007,61404156,61522407,61604168,61775230)+7 种基金the Key Frontier Scientific Research Program of the Chinese Academy of Sciences(No.QYZDB-SSW-JSC014)the Science and Technology Service Network Initiative of the Chinese Academy of Sciences,the Key R&D Program of Jiangsu Province(No.BE2017079)the Natural Science Foundation of Jiangsu Province(No.BK20160401)the China Postdoctoral Science Foundation(No.2016M591944)supported by the Open Fund of the State Key Laboratory of Luminescence and Applications(No.SKLA-2016-01)the Open Fund of the State Key Laboratory on Integrated Optoelectronics(Nos.IOSKL2016KF04,IOSKL2016KF07)the Seed Fund from SINANO,CAS(No.Y5AAQ51001)supported technically by Nano Fabrication Facility,Platform for Characterization&Test,Nano-X of SINANO,CAS
文摘c-plane GaN-based blue laser diodes（LDs） were fabricated with Al-free cladding layers（CLs） and deepened etching depth of mesa structure, so the aspect ratio of the far-field pattern（FFP） of the laser beam can be reduced to as low as 1.7, which is nearly the same as conventional AlGa In P-based red LDs. By using GaN CLs,the radiation angle of the laser beam θ⊥ is only 10.1° in the direction perpendicular to the junction plane. After forming a deeply etched mesa, the beam divergence angle parallel to the junction plane of FFP, θ;, increases from4.9° to 5.8°. After using the modified structure, the operation voltage of LD is effectively reduced by 2 V at an injection current of 50 mA, but the threshold current value increases. The etching damage may be one of the main reasons responsible for the increase of the threshold current.
文摘针对大型分块反射面天线面板调整次数多、效率低的问题,提出了一种从天线远场方向图反推出面板调整量进而快速调整的方法。应用物理光学(physical optics,PO)法建立了表面节点位移与远区电场的线性关系,将面板调整向量与远区辐射场强用线性方程组联系起来。利用奇异值分解(singular value decomposition,SVD)法求解线性方程组得调整向量,从而实现由方向图反推调整量的目的。对某工程案例进行了分析计算,给出了相应的数据与曲线,证明了所提方法的有效性,为大型天线反射面板的精确调整提供了指导。
