A full-polarimetric super-resolution algorithm with spatial smoothing processing is presented for one-dimensional(1-D)radar imaging.The coherence between scattering centers is minimized by using spatial smoothing pr...A full-polarimetric super-resolution algorithm with spatial smoothing processing is presented for one-dimensional(1-D)radar imaging.The coherence between scattering centers is minimized by using spatial smoothing processing(SSP).Then the range and polarimetric scattering matrix of the scattering centers are estimated.The impact of different lengths of the smoothing window on the imaging quality is mainly analyzed with different signal-to-noise ratios(SNR).Simulation and experimental results show that an improved radar super-resolution range profile and more precise estimation can be obtained by adjusting the length of the smoothing window under different SNR conditions.展开更多
Based on Evans’spatial smoothing preprocessing scheme,a new approach calledtwo-direction spatial smoothing preprocessing method is presented.It is proved that the decorre-lation,the effective aperture and the maximum...Based on Evans’spatial smoothing preprocessing scheme,a new approach calledtwo-direction spatial smoothing preprocessing method is presented.It is proved that the decorre-lation,the effective aperture and the maximum number of distinguishable coherent signals(whenarray size is given)of the new method are better than those of the Evans’method.Simulationresults give a comparison between the eigenvector spectrums produced by the two methods.展开更多
In this work,we study the Cauchy problem of the spatially homogeneous Landau equation with hard potentials in a close-to-equilibrium framework.We prove that the solution to the Cauchy problem enjoys the analytic regul...In this work,we study the Cauchy problem of the spatially homogeneous Landau equation with hard potentials in a close-to-equilibrium framework.We prove that the solution to the Cauchy problem enjoys the analytic regularizing effect of the time variable with an L^(2)initial datum for positive time.So that the smoothing effect of the Cauchy problem for the spatially homogeneous Landau equation with hard potentials is exactly same as heat equation.展开更多
A novel method to estimate DOA of coherent signals impinging on a uniform circular array( UCA) is presented in this paper. A virtual uniform linear array (VULA) is first derived by using spatial DFT technique, transfo...A novel method to estimate DOA of coherent signals impinging on a uniform circular array( UCA) is presented in this paper. A virtual uniform linear array (VULA) is first derived by using spatial DFT technique, transforming the UCA from element space to phase mode space to obtain the properties of ordinary ULA, and then the well known spatial smoothing technique is applied to the VULA so that the lost rank of covariance matrix due to signal coherence can be retrieved. This method makes it feasible to use the simple MUSIC algorithm to estimate DOA of coherent signals impinging on a UCA without heavy computation burden. Simulation results strongly verify the effectiveness of the algorithm.展开更多
The performance the quaternion-Capon( Q-Capon) beamformer degraded when suppressing the interferences that are coherent with the signal of interest( SOI). To tackle the problem,the spatial smoothing technique is a...The performance the quaternion-Capon( Q-Capon) beamformer degraded when suppressing the interferences that are coherent with the signal of interest( SOI). To tackle the problem,the spatial smoothing technique is adopted in quaternion domain to decorrelate the interferences by using linearly and uniformly spaced two-component electromagnetic vector-sensors. By averaging several translational invariant subarray quaternion covariance matrices,the quaternion spatial smoothing is performed to prevent the SOI cancellation phenomena caused by the presence of coherent interferences. It is demonstrated that the quaternion spatial smoothing Q-Capon beamformer can suppress the coherent interferences remarkably while the computational cost is lower than the complex domain long vector spatial smoothing counterpart. Theoretical analyses and simulation results validate the efficacy of the spatially smoothed Q-Capon beamformer in terms of coherent interference suppression capability.展开更多
In this study, the North China seismic region was selected as the study area, and evaluation of seismic hazard using the spatial smoothing seismicity model was performed. Firstly, the study area is divided into grids,...In this study, the North China seismic region was selected as the study area, and evaluation of seismic hazard using the spatial smoothing seismicity model was performed. Firstly, the study area is divided into grids, and some parameters (e. g. b-value, Mo, Me, azimuth and M-L relationship ) for each seismotectonic model were assigned. Secondly, using elliptical smoothing based on a seismotectonic background model, the statistical earthquake incidence rate in each grid is successively calculated. Lastly, the relevant ground motion attenuation relationship is chosen to assess seismic hazard of general sites. The maps for the distribution of horizontal peak ground acceleration with 10% probability of exceedance in 50 years were obtained by using the seismic hazard analysis method based on grid source. This seismicity model simplifies the methodology of probabilistic seismic hazard analysis, especially appropriate for those places where seismic tectonics is not yet clearly known. This method can provide valuable references for seismic zonation and seismic safety assessment for significant engineering projects.展开更多
为了提高重构相干信号测向算法的估计性能,降低算法运算量,提出了一种基于矩阵重构和酉变换方法的酉矩阵重构算法。该算法首先通过酉变换将阵列接收数据从复值计算转换为实值计算,使计算量大大降低;然后计算阵列协方差矩阵并进行特征值...为了提高重构相干信号测向算法的估计性能,降低算法运算量,提出了一种基于矩阵重构和酉变换方法的酉矩阵重构算法。该算法首先通过酉变换将阵列接收数据从复值计算转换为实值计算,使计算量大大降低;然后计算阵列协方差矩阵并进行特征值分解得到信号子空间,再将信号子空间重构为Toeplitz矩阵实现解相干并再次进行酉变换;最后通过特征值分解得到信号子空间并使用最小二乘法实现波达方向(direction of arrival,DOA)估计。相比于改进的旋转不变性的信号参数(estimation of signal parameters via rotational invariance techniques-like,ESPRIT-Like)算法和空间平滑处理算法,由于消除了噪声影响、构造了Toeplitz矩阵以及充分利用了数据的共轭信息,该算法的估计精度更高、具有更高的运算效率且在ESPRIT-Like算法失效的条件下新算法仍能有效估计DOA。本文算法的运行时间是ESPRIT-Like算法的71.2%,实验结果证明了该方法的有效性和真实性。展开更多
实时定位移动设备在电子对抗系统中至关重要,其性能主要取决于波达角(direction of arrival,DOA)的估计速度。低快拍是快速DOA估计的先决条件。目前基于稀疏重构算法的DOA估计具有适应低快拍的优势,但估计精度受限于初始观测矩阵,且估...实时定位移动设备在电子对抗系统中至关重要,其性能主要取决于波达角(direction of arrival,DOA)的估计速度。低快拍是快速DOA估计的先决条件。目前基于稀疏重构算法的DOA估计具有适应低快拍的优势,但估计精度受限于初始观测矩阵,且估计速度受限于观测矩阵高维度的多次迭代。为此,提出一种空间差分矩阵和稀疏重构耦合的低快拍下高精度快速估计算法。首先利用空间差分矩阵消除非相干信号和噪声对相干信号估计结果的影响,提升初始观测矩阵的准确度;然后对完备字典做前后空间平滑处理,克服高维度信号处理复杂难题,实现快速估计;最后分别估计非相干信号和相干信号。仿真验证结果表明,相比稀疏重构方法,所提方案初值敏感度显著降低,在保障精度相当甚至小幅度提升的前提下,运行时间复杂度降低50%以上。展开更多
为了提高传统空间平滑算法对相干信号的估计精度,提出了一种张量域空间平滑多重信号分类(Multiple Signal Classification,MUSIC)解相干算法。首先,利用四元数的正交特性重新构造极化域导向矢量;其次,考虑阵列接收数据固有的多维结构特...为了提高传统空间平滑算法对相干信号的估计精度,提出了一种张量域空间平滑多重信号分类(Multiple Signal Classification,MUSIC)解相干算法。首先,利用四元数的正交特性重新构造极化域导向矢量;其次,考虑阵列接收数据固有的多维结构特征,构造三阶张量表示的阵列接收数据模型;接着,借鉴二维空间平滑算法的思想,在张量接收数据模型中构建三阶张量子阵块,再使该子阵块在张量域进行前向空间平滑,继而得到平滑后的张量协方差矩阵;最后,通过高阶奇异值分解(Higher-order Singular Value Decomposition,HOSVD)得到信号子空间,利用降维MUSIC算法对相干信号源的二维波达方向(Direction of Arrival,DOA)进行估计,并根据已经获得的DOA信息求解出相干信号的极化参数。仿真结果表明,在信噪比为0 dB以及快拍数为100的情况下,该算法的估计精度比空间平滑算法提高了约70%,成功分辨概率提高了约89%,且无需进行四维谱峰搜索,降低了算法的复杂度,对相干信号具有更高的估计精度和分辨能力。展开更多
文中提出一种二维空间相干信号波达方向(Direction of Arrival,DOA)估计方法。该方法首先对L形阵接收数据协方差矩阵进行共轭重构,将原协方差矩阵的平方与重构矩阵的平方相加后求均值,得到新协方差矩阵。然后采用前后向空间平滑技术对...文中提出一种二维空间相干信号波达方向(Direction of Arrival,DOA)估计方法。该方法首先对L形阵接收数据协方差矩阵进行共轭重构,将原协方差矩阵的平方与重构矩阵的平方相加后求均值,得到新协方差矩阵。然后采用前后向空间平滑技术对新协方差矩阵进行预处理,最后通过Root-MUSIC算法进行DOA估计。仿真实验和湖试数据分析结果表明,与常规方法相比,文中方法避免了谱峰搜索,减小了计算量,提高了相干信号DOA估计的分辨成功概率和估计精度,具有较高的工程应用价值。展开更多
This study proposed a random Smoothed Particle Hydrodynamics method for analyzing the post-failure behavior of landslides,which is based on the Karhunen-Loeve(K-L) expansion,the non-Newtonian fluid model,and the OpenM...This study proposed a random Smoothed Particle Hydrodynamics method for analyzing the post-failure behavior of landslides,which is based on the Karhunen-Loeve(K-L) expansion,the non-Newtonian fluid model,and the OpenMP parallel framework.Then,the applicability of this method was validated by comparing the generated random field with theoretical result and by simulating the post-failure process of an actual landslide.Thereafter,an illustrative landslide example was created and simulated to obtain the spatial variability effect of internal friction angle on the post-failure behavior of landslides under different coefficients of variation(COVs) and correlation lengths(CLs).As a conclusion,the reinforcement with materials of a larger friction angle can reduce the runout distance and impact the force of a landslide.As the increase of COV,the distribution range of influence zones also increases,which indicates that the deviation of influence zones becomes large.In addition,the correlation length in Monte Carlo simulations should not be too small,otherwise the variation range of influence zones will be underestimated.展开更多
Spectrum sensing is the key problem for Cognitive Radio(CR) systems.A method based on the Peak-to-Average Amplitude-Ratio(PAAR) of the Spatial Spectrum(SS) of the received signals is proposed to sense the available sp...Spectrum sensing is the key problem for Cognitive Radio(CR) systems.A method based on the Peak-to-Average Amplitude-Ratio(PAAR) of the Spatial Spectrum(SS) of the received signals is proposed to sense the available spectrum for the cognitive users with the help of the multiple antennas at the receiver of the cognitive users.The greatest advantage of the new method is that it requires no information of the noise power and is free of the noise power uncertainty.Both the simulation and the analytical results show that the proposed method is robust to noise uncertainty,and greatly outperform the classical Energy Detector(ED) method.展开更多
基金Supported by the National Naturral Science Foundation of China(61301191)
文摘A full-polarimetric super-resolution algorithm with spatial smoothing processing is presented for one-dimensional(1-D)radar imaging.The coherence between scattering centers is minimized by using spatial smoothing processing(SSP).Then the range and polarimetric scattering matrix of the scattering centers are estimated.The impact of different lengths of the smoothing window on the imaging quality is mainly analyzed with different signal-to-noise ratios(SNR).Simulation and experimental results show that an improved radar super-resolution range profile and more precise estimation can be obtained by adjusting the length of the smoothing window under different SNR conditions.
文摘Based on Evans’spatial smoothing preprocessing scheme,a new approach calledtwo-direction spatial smoothing preprocessing method is presented.It is proved that the decorre-lation,the effective aperture and the maximum number of distinguishable coherent signals(whenarray size is given)of the new method are better than those of the Evans’method.Simulationresults give a comparison between the eigenvector spectrums produced by the two methods.
基金the NSFC(No.12031006)and the Fundamental Research Funds for the Central Universities of China.
文摘In this work,we study the Cauchy problem of the spatially homogeneous Landau equation with hard potentials in a close-to-equilibrium framework.We prove that the solution to the Cauchy problem enjoys the analytic regularizing effect of the time variable with an L^(2)initial datum for positive time.So that the smoothing effect of the Cauchy problem for the spatially homogeneous Landau equation with hard potentials is exactly same as heat equation.
文摘A novel method to estimate DOA of coherent signals impinging on a uniform circular array( UCA) is presented in this paper. A virtual uniform linear array (VULA) is first derived by using spatial DFT technique, transforming the UCA from element space to phase mode space to obtain the properties of ordinary ULA, and then the well known spatial smoothing technique is applied to the VULA so that the lost rank of covariance matrix due to signal coherence can be retrieved. This method makes it feasible to use the simple MUSIC algorithm to estimate DOA of coherent signals impinging on a UCA without heavy computation burden. Simulation results strongly verify the effectiveness of the algorithm.
基金Supported by the National Natural Science Foundation of China(61331019)
文摘The performance the quaternion-Capon( Q-Capon) beamformer degraded when suppressing the interferences that are coherent with the signal of interest( SOI). To tackle the problem,the spatial smoothing technique is adopted in quaternion domain to decorrelate the interferences by using linearly and uniformly spaced two-component electromagnetic vector-sensors. By averaging several translational invariant subarray quaternion covariance matrices,the quaternion spatial smoothing is performed to prevent the SOI cancellation phenomena caused by the presence of coherent interferences. It is demonstrated that the quaternion spatial smoothing Q-Capon beamformer can suppress the coherent interferences remarkably while the computational cost is lower than the complex domain long vector spatial smoothing counterpart. Theoretical analyses and simulation results validate the efficacy of the spatially smoothed Q-Capon beamformer in terms of coherent interference suppression capability.
基金funded by the Special Fund for Fundamental Research of Central-level Public Interest Institutions,China(ZDJ2011-13)
文摘In this study, the North China seismic region was selected as the study area, and evaluation of seismic hazard using the spatial smoothing seismicity model was performed. Firstly, the study area is divided into grids, and some parameters (e. g. b-value, Mo, Me, azimuth and M-L relationship ) for each seismotectonic model were assigned. Secondly, using elliptical smoothing based on a seismotectonic background model, the statistical earthquake incidence rate in each grid is successively calculated. Lastly, the relevant ground motion attenuation relationship is chosen to assess seismic hazard of general sites. The maps for the distribution of horizontal peak ground acceleration with 10% probability of exceedance in 50 years were obtained by using the seismic hazard analysis method based on grid source. This seismicity model simplifies the methodology of probabilistic seismic hazard analysis, especially appropriate for those places where seismic tectonics is not yet clearly known. This method can provide valuable references for seismic zonation and seismic safety assessment for significant engineering projects.
文摘为了提高重构相干信号测向算法的估计性能,降低算法运算量,提出了一种基于矩阵重构和酉变换方法的酉矩阵重构算法。该算法首先通过酉变换将阵列接收数据从复值计算转换为实值计算,使计算量大大降低;然后计算阵列协方差矩阵并进行特征值分解得到信号子空间,再将信号子空间重构为Toeplitz矩阵实现解相干并再次进行酉变换;最后通过特征值分解得到信号子空间并使用最小二乘法实现波达方向(direction of arrival,DOA)估计。相比于改进的旋转不变性的信号参数(estimation of signal parameters via rotational invariance techniques-like,ESPRIT-Like)算法和空间平滑处理算法,由于消除了噪声影响、构造了Toeplitz矩阵以及充分利用了数据的共轭信息,该算法的估计精度更高、具有更高的运算效率且在ESPRIT-Like算法失效的条件下新算法仍能有效估计DOA。本文算法的运行时间是ESPRIT-Like算法的71.2%,实验结果证明了该方法的有效性和真实性。
文摘实时定位移动设备在电子对抗系统中至关重要,其性能主要取决于波达角(direction of arrival,DOA)的估计速度。低快拍是快速DOA估计的先决条件。目前基于稀疏重构算法的DOA估计具有适应低快拍的优势,但估计精度受限于初始观测矩阵,且估计速度受限于观测矩阵高维度的多次迭代。为此,提出一种空间差分矩阵和稀疏重构耦合的低快拍下高精度快速估计算法。首先利用空间差分矩阵消除非相干信号和噪声对相干信号估计结果的影响,提升初始观测矩阵的准确度;然后对完备字典做前后空间平滑处理,克服高维度信号处理复杂难题,实现快速估计;最后分别估计非相干信号和相干信号。仿真验证结果表明,相比稀疏重构方法,所提方案初值敏感度显著降低,在保障精度相当甚至小幅度提升的前提下,运行时间复杂度降低50%以上。
文摘为了提高传统空间平滑算法对相干信号的估计精度,提出了一种张量域空间平滑多重信号分类(Multiple Signal Classification,MUSIC)解相干算法。首先,利用四元数的正交特性重新构造极化域导向矢量;其次,考虑阵列接收数据固有的多维结构特征,构造三阶张量表示的阵列接收数据模型;接着,借鉴二维空间平滑算法的思想,在张量接收数据模型中构建三阶张量子阵块,再使该子阵块在张量域进行前向空间平滑,继而得到平滑后的张量协方差矩阵;最后,通过高阶奇异值分解(Higher-order Singular Value Decomposition,HOSVD)得到信号子空间,利用降维MUSIC算法对相干信号源的二维波达方向(Direction of Arrival,DOA)进行估计,并根据已经获得的DOA信息求解出相干信号的极化参数。仿真结果表明,在信噪比为0 dB以及快拍数为100的情况下,该算法的估计精度比空间平滑算法提高了约70%,成功分辨概率提高了约89%,且无需进行四维谱峰搜索,降低了算法的复杂度,对相干信号具有更高的估计精度和分辨能力。
文摘文中提出一种二维空间相干信号波达方向(Direction of Arrival,DOA)估计方法。该方法首先对L形阵接收数据协方差矩阵进行共轭重构,将原协方差矩阵的平方与重构矩阵的平方相加后求均值,得到新协方差矩阵。然后采用前后向空间平滑技术对新协方差矩阵进行预处理,最后通过Root-MUSIC算法进行DOA估计。仿真实验和湖试数据分析结果表明,与常规方法相比,文中方法避免了谱峰搜索,减小了计算量,提高了相干信号DOA估计的分辨成功概率和估计精度,具有较高的工程应用价值。
基金This work is supported by the Natural Science Foundation of China(NSFC Grant No.51808192,51879091,41630638)the Natural Science Foundation of Jiangsu Province(Grant No.BK20170887)the China Postdoctoral Science Foundation(Grant Nos.2017M611673 and 2018T110432).We thank Ms.Ruihua Yu for her contribution in compiling some of the figures in this work.
文摘This study proposed a random Smoothed Particle Hydrodynamics method for analyzing the post-failure behavior of landslides,which is based on the Karhunen-Loeve(K-L) expansion,the non-Newtonian fluid model,and the OpenMP parallel framework.Then,the applicability of this method was validated by comparing the generated random field with theoretical result and by simulating the post-failure process of an actual landslide.Thereafter,an illustrative landslide example was created and simulated to obtain the spatial variability effect of internal friction angle on the post-failure behavior of landslides under different coefficients of variation(COVs) and correlation lengths(CLs).As a conclusion,the reinforcement with materials of a larger friction angle can reduce the runout distance and impact the force of a landslide.As the increase of COV,the distribution range of influence zones also increases,which indicates that the deviation of influence zones becomes large.In addition,the correlation length in Monte Carlo simulations should not be too small,otherwise the variation range of influence zones will be underestimated.
基金Supported by the National Natural Science Foundation of China (No. 60602053)Program for New Century Excellent Talents in University (NCET-08-0891)+2 种基金the Natural Science Foundation of Shaanxi Province (2010JQ80241)the Natural Science Foundation of Hubei Province (2009 CDB308)the Fund from Education Department of Shaanxi Government (2010JK836)
文摘Spectrum sensing is the key problem for Cognitive Radio(CR) systems.A method based on the Peak-to-Average Amplitude-Ratio(PAAR) of the Spatial Spectrum(SS) of the received signals is proposed to sense the available spectrum for the cognitive users with the help of the multiple antennas at the receiver of the cognitive users.The greatest advantage of the new method is that it requires no information of the noise power and is free of the noise power uncertainty.Both the simulation and the analytical results show that the proposed method is robust to noise uncertainty,and greatly outperform the classical Energy Detector(ED) method.