与均匀阵列相比,稀疏阵列可以使天线阵列成本降低,减少数据处理,同时带来更大的阵列孔径提高信号解析能力,在信号处理中有着广泛的应用。但是由于其排布的不规则性,计算量较大,二维面阵合成协方差矩阵存在空洞,对角度估计的准确性造成...与均匀阵列相比,稀疏阵列可以使天线阵列成本降低,减少数据处理,同时带来更大的阵列孔径提高信号解析能力,在信号处理中有着广泛的应用。但是由于其排布的不规则性,计算量较大,二维面阵合成协方差矩阵存在空洞,对角度估计的准确性造成负面影响,增强了系统对噪声的敏感度。为了克服这些问题,本文提出了一种新的角度估计方法,采用截断核范数以降低噪声的影响,并通过ℓ_(p)范数优化提升信号的稀疏表示,利用交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)算法构造子问题恢复出完整的阵列信号。随后采用子阵划分技术和基于最小二乘的传播算子模型(Propagator Method,PM)对恢复的信号处理,精确估计信号源的方位和俯仰角。仿真结果表明,所提出的角度估计算法在角度精度和时间复杂度方面具有优越性。展开更多
This paper presents an extended sequential element rejection and admission(SERA)topology optimizationmethod with a region partitioning strategy.Based on the partitioning of a design domain into solid regions and weak ...This paper presents an extended sequential element rejection and admission(SERA)topology optimizationmethod with a region partitioning strategy.Based on the partitioning of a design domain into solid regions and weak regions,the proposed optimizationmethod sequentially implements finite element analysis(FEA)in these regions.After standard FEA in the solid regions,the boundary displacement of the weak regions is constrained using the numerical solution of the solid regions as Dirichlet boundary conditions.This treatment can alleviate the negative effect of the material interpolation model of the topology optimization method in the weak regions,such as the condition number of the structural global stiffness matrix.For optimization,in which the forward problem requires nonlinear structural analysis,a linear solver can be applied in weak regions to avoid numerical singularities caused by the over-deformedmesh.To enhance the robustness of the proposedmethod,the nonmanifold point and island are identified and handled separately.The performance of the proposed method is verified by three 2D minimum compliance examples.展开更多
Surface sediment samples from Taihu Lake in China and its inflow rivers,along with two lake sediment core samples,were collected and analyzed for organophosphate esters(OPEs).The concentrations of total OPEs varied fr...Surface sediment samples from Taihu Lake in China and its inflow rivers,along with two lake sediment core samples,were collected and analyzed for organophosphate esters(OPEs).The concentrations of total OPEs varied from 28.60 ng/g to 158.72 ng/g(median:54.25 ng/g)in river surface sediment and from 62.57 ng/g to 326.84 ng/g(median:86.37 ng/g)in lake sediment.Tributyl phosphate(TnBP)was the predominant compound in river surface sediment,and tris(2-butoxyethyl)phosphate was predominant in lake sediment.High contamination occurred in the north-west region,which was related to the high level of urbanization and high usage of OPEs.The sediment–water partition coefficients of OPEs(log_(Koc))were calculated,showing a significant correlation with logKow(p<0.05).The concentration and composition of OPEs in two sediment cores varied due to the different sampling locations,with more OPE species found in the northern region than in the southern one.Principal component analysis and positive matrix factorization indicated that sewage discharges,vehicle emissions,and atmospheric deposition were the possible sources of OPEs in Taihu Lake sediments.Tris(1-chloro-2-propyl)phosphate,tris(2-chloroethyl)phosphate,and TnBP were the main OPEs causing ecological risks.展开更多
文摘与均匀阵列相比,稀疏阵列可以使天线阵列成本降低,减少数据处理,同时带来更大的阵列孔径提高信号解析能力,在信号处理中有着广泛的应用。但是由于其排布的不规则性,计算量较大,二维面阵合成协方差矩阵存在空洞,对角度估计的准确性造成负面影响,增强了系统对噪声的敏感度。为了克服这些问题,本文提出了一种新的角度估计方法,采用截断核范数以降低噪声的影响,并通过ℓ_(p)范数优化提升信号的稀疏表示,利用交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)算法构造子问题恢复出完整的阵列信号。随后采用子阵划分技术和基于最小二乘的传播算子模型(Propagator Method,PM)对恢复的信号处理,精确估计信号源的方位和俯仰角。仿真结果表明,所提出的角度估计算法在角度精度和时间复杂度方面具有优越性。
基金supported by the National Science Foundation of China (Grant No.51675506).
文摘This paper presents an extended sequential element rejection and admission(SERA)topology optimizationmethod with a region partitioning strategy.Based on the partitioning of a design domain into solid regions and weak regions,the proposed optimizationmethod sequentially implements finite element analysis(FEA)in these regions.After standard FEA in the solid regions,the boundary displacement of the weak regions is constrained using the numerical solution of the solid regions as Dirichlet boundary conditions.This treatment can alleviate the negative effect of the material interpolation model of the topology optimization method in the weak regions,such as the condition number of the structural global stiffness matrix.For optimization,in which the forward problem requires nonlinear structural analysis,a linear solver can be applied in weak regions to avoid numerical singularities caused by the over-deformedmesh.To enhance the robustness of the proposedmethod,the nonmanifold point and island are identified and handled separately.The performance of the proposed method is verified by three 2D minimum compliance examples.
基金funded by the Special Fund for Basic Scientific Research of Central Public Research Institutes(2019YSKY-022,2020YSKY-018).
文摘Surface sediment samples from Taihu Lake in China and its inflow rivers,along with two lake sediment core samples,were collected and analyzed for organophosphate esters(OPEs).The concentrations of total OPEs varied from 28.60 ng/g to 158.72 ng/g(median:54.25 ng/g)in river surface sediment and from 62.57 ng/g to 326.84 ng/g(median:86.37 ng/g)in lake sediment.Tributyl phosphate(TnBP)was the predominant compound in river surface sediment,and tris(2-butoxyethyl)phosphate was predominant in lake sediment.High contamination occurred in the north-west region,which was related to the high level of urbanization and high usage of OPEs.The sediment–water partition coefficients of OPEs(log_(Koc))were calculated,showing a significant correlation with logKow(p<0.05).The concentration and composition of OPEs in two sediment cores varied due to the different sampling locations,with more OPE species found in the northern region than in the southern one.Principal component analysis and positive matrix factorization indicated that sewage discharges,vehicle emissions,and atmospheric deposition were the possible sources of OPEs in Taihu Lake sediments.Tris(1-chloro-2-propyl)phosphate,tris(2-chloroethyl)phosphate,and TnBP were the main OPEs causing ecological risks.
