多尺度非均匀背景为不同尺度和形状且在空间上分布不均匀的粗糙结构。本文针对多尺度非均匀粗糙背景散射特性快速计算问题,提出了基于散射中心方法的参数化表征模型。多尺度非均匀背景的散射场一般由地表大尺度表面所产生的镜反射分量...多尺度非均匀背景为不同尺度和形状且在空间上分布不均匀的粗糙结构。本文针对多尺度非均匀粗糙背景散射特性快速计算问题,提出了基于散射中心方法的参数化表征模型。多尺度非均匀背景的散射场一般由地表大尺度表面所产生的镜反射分量、大尺度表面几何不连续处所产生的绕射分量和地表小尺度粗糙面引起的漫散射分量共同组成。传统雷达目标散射中心建模采用分布型、局部型和滑动型散射中心模型(scattering center model, SCM)表征目标的反射和绕射散射;但是,传统散射中心表征形式仅能描述大尺度光滑表面、几何不连续处的散射场,无法描述小尺度粗糙面的散射效应。本文结合粗糙面的相干-非相干散射理论,在大尺度地形散射中心表征模型的基础上,利用相干模型修正小尺度粗糙面对大尺度表面散射场幅度的影响;利用双向反射分布函数(bidirectional reflectance distribution function, BRDF)建立非相干散射的参数化表征形式。对两种非均匀多尺度背景的散射特性进行参数化表征,并采用商业软件高频求解器对计算结果的精度和效率进行了校验,证明了粗糙背景散射中心参数化建模方法的可行性。展开更多
In past years ,people were hardly aware of Mapping Knowledge between Environments when dealing with problems,did not consider the ability of their constraint and introduction to handle cognition problem under incomple...In past years ,people were hardly aware of Mapping Knowledge between Environments when dealing with problems,did not consider the ability of their constraint and introduction to handle cognition problem under incomplete information environment. This paper firstly points out the importance of explicit representation on background knowledge,then gives a method that deals with imprecise infor mation aggregation using generalized rough set theory. This process involves representation and acquiring about background knowledge.展开更多
此前角闪烁特性的研究对象多为偶极子或自由空间中的典型目标,而海、地粗糙面环境中雷达目标角闪烁特性研究的需求更为迫切。采用矩量法与矩阵UV分解相结合(method of moments with the UV,MOM-UV)的快速计算方法,仿真求得PM谱粗糙面及...此前角闪烁特性的研究对象多为偶极子或自由空间中的典型目标,而海、地粗糙面环境中雷达目标角闪烁特性研究的需求更为迫切。采用矩量法与矩阵UV分解相结合(method of moments with the UV,MOM-UV)的快速计算方法,仿真求得PM谱粗糙面及其上方二维目标的各成分感应电流。再利用相位梯度法得到复合散射角闪烁线偏差的精确计算结果,并进一步分析各成分感应电流对角闪烁的贡献,探究耦合对于目标角闪烁特性的影响。展开更多
Estimation of an accurate macro velocity model plays an important role in seismic imag- ing and model parameter inversion. Full waveform inversion （FWI） is the classical data-domain inver- sion method. However, the ...Estimation of an accurate macro velocity model plays an important role in seismic imag- ing and model parameter inversion. Full waveform inversion （FWI） is the classical data-domain inver- sion method. However, the misfit function of FWI is highly nonlinear, and the local optimization cannot prevent convergence of the misfit function toward local minima. To converge to the global minimum, FWI needs a good initial model or reliable low frequency component and long offset data. In this article, we present a wave-equation-based reflection traveltime tomography （WERTT） method, which can pro- vide a good background model （initial model） for FWI and （least-square） pre-stack depth migration （LS-PSDM）. First, the velocity model is decomposed into a low-wavenumber component （background velocity） and a high-wavenumber component （reflectivity）. Second, the primary reflection wave is pre- dicted by wave-equation demigration, and the reflection traveltime is calculated by an automatic picking method. Finally, the misfit function of the 12-norm of the reflection traveltime residuals is mini- mized by a gradient-based method. Numerical tests show that the proposed method can invert a good background model, which can be used as an initial model for LS-PSDM or FWI.展开更多
This paper introduces an installation for quickly classifying automobile's metal reflectors based on their roughness. The measuring principle and the mechanical structure are presented. Schematics of circuits and ...This paper introduces an installation for quickly classifying automobile's metal reflectors based on their roughness. The measuring principle and the mechanical structure are presented. Schematics of circuits and experimental results are given. Elimination and reduction of the effect of background lights or different bulbs on the measuring results are also described in detail.展开更多
文摘多尺度非均匀背景为不同尺度和形状且在空间上分布不均匀的粗糙结构。本文针对多尺度非均匀粗糙背景散射特性快速计算问题,提出了基于散射中心方法的参数化表征模型。多尺度非均匀背景的散射场一般由地表大尺度表面所产生的镜反射分量、大尺度表面几何不连续处所产生的绕射分量和地表小尺度粗糙面引起的漫散射分量共同组成。传统雷达目标散射中心建模采用分布型、局部型和滑动型散射中心模型(scattering center model, SCM)表征目标的反射和绕射散射;但是,传统散射中心表征形式仅能描述大尺度光滑表面、几何不连续处的散射场,无法描述小尺度粗糙面的散射效应。本文结合粗糙面的相干-非相干散射理论,在大尺度地形散射中心表征模型的基础上,利用相干模型修正小尺度粗糙面对大尺度表面散射场幅度的影响;利用双向反射分布函数(bidirectional reflectance distribution function, BRDF)建立非相干散射的参数化表征形式。对两种非均匀多尺度背景的散射特性进行参数化表征,并采用商业软件高频求解器对计算结果的精度和效率进行了校验,证明了粗糙背景散射中心参数化建模方法的可行性。
文摘In past years ,people were hardly aware of Mapping Knowledge between Environments when dealing with problems,did not consider the ability of their constraint and introduction to handle cognition problem under incomplete information environment. This paper firstly points out the importance of explicit representation on background knowledge,then gives a method that deals with imprecise infor mation aggregation using generalized rough set theory. This process involves representation and acquiring about background knowledge.
文摘此前角闪烁特性的研究对象多为偶极子或自由空间中的典型目标,而海、地粗糙面环境中雷达目标角闪烁特性研究的需求更为迫切。采用矩量法与矩阵UV分解相结合(method of moments with the UV,MOM-UV)的快速计算方法,仿真求得PM谱粗糙面及其上方二维目标的各成分感应电流。再利用相位梯度法得到复合散射角闪烁线偏差的精确计算结果,并进一步分析各成分感应电流对角闪烁的贡献,探究耦合对于目标角闪烁特性的影响。
基金financially supported by the National Natural Science Foundation of China(No.41374117)the‘973’Project of China(No.2011 CB201002)the Great and Special Projects of China(Nos.2011ZX05003-003,2011ZX05005-005-008HZ,and 2011ZX05006-002)
文摘Estimation of an accurate macro velocity model plays an important role in seismic imag- ing and model parameter inversion. Full waveform inversion （FWI） is the classical data-domain inver- sion method. However, the misfit function of FWI is highly nonlinear, and the local optimization cannot prevent convergence of the misfit function toward local minima. To converge to the global minimum, FWI needs a good initial model or reliable low frequency component and long offset data. In this article, we present a wave-equation-based reflection traveltime tomography （WERTT） method, which can pro- vide a good background model （initial model） for FWI and （least-square） pre-stack depth migration （LS-PSDM）. First, the velocity model is decomposed into a low-wavenumber component （background velocity） and a high-wavenumber component （reflectivity）. Second, the primary reflection wave is pre- dicted by wave-equation demigration, and the reflection traveltime is calculated by an automatic picking method. Finally, the misfit function of the 12-norm of the reflection traveltime residuals is mini- mized by a gradient-based method. Numerical tests show that the proposed method can invert a good background model, which can be used as an initial model for LS-PSDM or FWI.
文摘This paper introduces an installation for quickly classifying automobile's metal reflectors based on their roughness. The measuring principle and the mechanical structure are presented. Schematics of circuits and experimental results are given. Elimination and reduction of the effect of background lights or different bulbs on the measuring results are also described in detail.
