A compressive near-field millimeter wave(MMW)imaging algorithm is proposed.From the compressed sensing(CS)theory,the compressive near-field MMW imaging process can be considered to reconstruct an image from the under-...A compressive near-field millimeter wave(MMW)imaging algorithm is proposed.From the compressed sensing(CS)theory,the compressive near-field MMW imaging process can be considered to reconstruct an image from the under-sampled sparse data.The Gini index(GI)has been founded that it is the only sparsity measure that has all sparsity attributes that are called Robin Hood,Scaling,Rising Tide,Cloning,Bill Gates,and Babies.By combining the total variation(TV)operator,the GI-TV mixed regularization introduced compressive near-field MMW imaging model is proposed.In addition,the corresponding algorithm based on a primal-dual framework is also proposed.Experimental results demonstrate that the proposed GI-TV mixed regularization algorithm has superior convergence and stability performance compared with the widely used l1-TV mixed regularization algorithm.展开更多
为提升柱塞泵振动数据采集质量、故障诊断准确率和诊断模型的鲁棒性,对采集柱塞泵振动数据时,确定传感器安装位置的方法展开研究,分析了传感器的安装位置对柱塞泵振动数据质量的影响,给出了传感器安装位置评价方法。利用AMESim构建了力...为提升柱塞泵振动数据采集质量、故障诊断准确率和诊断模型的鲁棒性,对采集柱塞泵振动数据时,确定传感器安装位置的方法展开研究,分析了传感器的安装位置对柱塞泵振动数据质量的影响,给出了传感器安装位置评价方法。利用AMESim构建了力士乐A11VO系列9柱塞泵仿真模型,通过研究传感器各项性能指标、柱塞泵结构及运动机理,分析得到柱塞泵振动数据采集实验中合理的传感器安装位置。提出基于平方包络的基尼指数(Gini index of square envelope,GISE)柱塞泵故障振动信号质量评价方法,并设计柱塞泵振动数据采集实验进行验证。得到GISE等4种稀疏性指标的指示结果与柱塞泵结构分析结果一致,分析并证明了GISE指标在柱塞泵信号评估上的有效性与优越性。展开更多
The number and composition of species in a community can be quantified withα-diversity indices,including species richness(R),Simpson’s index(D),and the Shannon-Wiener index(H΄).In forest communities,there are large ...The number and composition of species in a community can be quantified withα-diversity indices,including species richness(R),Simpson’s index(D),and the Shannon-Wiener index(H΄).In forest communities,there are large variations in tree size among species and individu-als of the same species,which result in differences in eco-logical processes and ecosystem functions.However,tree size inequality(TSI)has been largely neglected in studies using the available diversity indices.The TSI in the diameter at breast height(DBH)data for each of 99920 m×20 m forest census quadrats was quantified using the Gini index(GI),a measure of the inequality of size distribution.The generalized performance equation was used to describe the rotated and right-shifted Lorenz curve of the cumulative proportion of DBH and the cumulative proportion of number of trees per quadrat.We also examined the relationships ofα-diversity indices with the GI using correlation tests.The generalized performance equation effectively described the rotated and right-shifted Lorenz curve of DBH distributions,with most root-mean-square errors(990 out of 999 quadrats)being<0.0030.There were significant positive correlations between each of threeα-diversity indices(i.e.,R,D,and H’)and the GI.Nevertheless,the total abundance of trees in each quadrat did not significantly influence the GI.This means that the TSI increased with increasing spe-cies diversity.Thus,two new indices are proposed that can balanceα-diversity against the extent of TSI in the com-munity:(1−GI)×D,and(1−GI)×H’.These new indices were significantly correlated with the original D and H΄,and did not increase the extent of variation within each group of indices.This study presents a useful tool for quantifying both species diversity and the variation in tree sizes in forest communities,especially in the face of cumulative species loss under global climate change.展开更多
为准确提取被强背景噪声掩盖的滚动轴承故障信息,提出一种参数优化特征模态分解(parameter-optimized feature mode decomposition,POFMD)方法。首先,为解决特征模态分解(feature mode decomposition,FMD)方法的输入参数依赖人工经验选...为准确提取被强背景噪声掩盖的滚动轴承故障信息,提出一种参数优化特征模态分解(parameter-optimized feature mode decomposition,POFMD)方法。首先,为解决特征模态分解(feature mode decomposition,FMD)方法的输入参数依赖人工经验选取的问题,以平方包络谱峭度(kurtosis of the square envelope spectrum,KSES)为权值,结合平方包络谱基尼系数(Gini index of the square envelope spectrum,GISES)构建加权平方包络谱基尼系数(weighted Gini index of the square envelope spectrum,WGISES)作为目标函数,通过优化算法确定FMD的最优参数组合;其次,为解决FMD的主模态分量难以选取的问题,通过计算所分解模态分量的KSES值选取主模态分量;最后,通过包络谱分析实现故障诊断。经仿真信号和实测信号分析,验证了POFMD在强背景噪声下滚动轴承故障诊断中的有效性。与变分模态分解、最大相关峭度解卷积和谱峭度相比,POFMD有更优越的故障特征提取性能。展开更多
在全球变暖和人类活动的背景下,降水在年内分布上发生了比较大的变化,对人民生产生活产生了巨大的影响,这一影响在城市化较高的地区尤为明显。基于多源降水数据(降水产品数据和气象站点数据)和夜间灯光数据,选定中国的长三角城市群作为...在全球变暖和人类活动的背景下,降水在年内分布上发生了比较大的变化,对人民生产生活产生了巨大的影响,这一影响在城市化较高的地区尤为明显。基于多源降水数据(降水产品数据和气象站点数据)和夜间灯光数据,选定中国的长三角城市群作为研究区域,将基尼系数(Gini Index,GI)作为降水集中度的指标,利用Theil-Sen Median斜率估计和Mann-Kendall显著性检验进行趋势分析,最后通过相关性分析探究城市化程度与降水集中度的关系。研究结果表明:(1)CHIRPS(Climate Hazards Group InfraRed Precipitation with Station Data)数据计算得到的GI与站点数据结果的均方根误差为0.036,远小于CMFD数据(0.067)和MSWEP数据(0.083)的结果,表明CHIRPS数据具有最佳的适用性;(2)长三角城市群的降水不均匀性从南向北逐渐增加,并在城市群中部和西部呈现出显著上升的趋势,研究区域内的降水年内分布将会朝着集中分布的方向发展,极端降水事件出现的可能性增加;(3)城市化对降水集中度主要起到促进作用,城市的快速发展使得降水不均匀性增强,并且在城市群内的南京市、无锡市和镇江市等地区更为显著,更有可能发生城市内涝等灾害。研究对于城市的防洪设计、城市道路排水管道的设计和城市防洪应急响应预案的编制具有参考意义。展开更多
基金supported in part by the National Natural Science Foundation of China under Grants No.62027803,No.61601096,No.61971111,No.61801089,and No.61701095in part by the Science and Technology Program under Grants No.8091C24,No.80904020405,No.2021JCJQJJ0949,and No.2022JCJQJJ0784in part by Industrial Technology Development Program under Grant No.2020110C041.
文摘A compressive near-field millimeter wave(MMW)imaging algorithm is proposed.From the compressed sensing(CS)theory,the compressive near-field MMW imaging process can be considered to reconstruct an image from the under-sampled sparse data.The Gini index(GI)has been founded that it is the only sparsity measure that has all sparsity attributes that are called Robin Hood,Scaling,Rising Tide,Cloning,Bill Gates,and Babies.By combining the total variation(TV)operator,the GI-TV mixed regularization introduced compressive near-field MMW imaging model is proposed.In addition,the corresponding algorithm based on a primal-dual framework is also proposed.Experimental results demonstrate that the proposed GI-TV mixed regularization algorithm has superior convergence and stability performance compared with the widely used l1-TV mixed regularization algorithm.
文摘为提升柱塞泵振动数据采集质量、故障诊断准确率和诊断模型的鲁棒性,对采集柱塞泵振动数据时,确定传感器安装位置的方法展开研究,分析了传感器的安装位置对柱塞泵振动数据质量的影响,给出了传感器安装位置评价方法。利用AMESim构建了力士乐A11VO系列9柱塞泵仿真模型,通过研究传感器各项性能指标、柱塞泵结构及运动机理,分析得到柱塞泵振动数据采集实验中合理的传感器安装位置。提出基于平方包络的基尼指数(Gini index of square envelope,GISE)柱塞泵故障振动信号质量评价方法,并设计柱塞泵振动数据采集实验进行验证。得到GISE等4种稀疏性指标的指示结果与柱塞泵结构分析结果一致,分析并证明了GISE指标在柱塞泵信号评估上的有效性与优越性。
基金supported by the National Natural Science Foundation of China(32101260).
文摘The number and composition of species in a community can be quantified withα-diversity indices,including species richness(R),Simpson’s index(D),and the Shannon-Wiener index(H΄).In forest communities,there are large variations in tree size among species and individu-als of the same species,which result in differences in eco-logical processes and ecosystem functions.However,tree size inequality(TSI)has been largely neglected in studies using the available diversity indices.The TSI in the diameter at breast height(DBH)data for each of 99920 m×20 m forest census quadrats was quantified using the Gini index(GI),a measure of the inequality of size distribution.The generalized performance equation was used to describe the rotated and right-shifted Lorenz curve of the cumulative proportion of DBH and the cumulative proportion of number of trees per quadrat.We also examined the relationships ofα-diversity indices with the GI using correlation tests.The generalized performance equation effectively described the rotated and right-shifted Lorenz curve of DBH distributions,with most root-mean-square errors(990 out of 999 quadrats)being<0.0030.There were significant positive correlations between each of threeα-diversity indices(i.e.,R,D,and H’)and the GI.Nevertheless,the total abundance of trees in each quadrat did not significantly influence the GI.This means that the TSI increased with increasing spe-cies diversity.Thus,two new indices are proposed that can balanceα-diversity against the extent of TSI in the com-munity:(1−GI)×D,and(1−GI)×H’.These new indices were significantly correlated with the original D and H΄,and did not increase the extent of variation within each group of indices.This study presents a useful tool for quantifying both species diversity and the variation in tree sizes in forest communities,especially in the face of cumulative species loss under global climate change.
文摘为准确提取被强背景噪声掩盖的滚动轴承故障信息,提出一种参数优化特征模态分解(parameter-optimized feature mode decomposition,POFMD)方法。首先,为解决特征模态分解(feature mode decomposition,FMD)方法的输入参数依赖人工经验选取的问题,以平方包络谱峭度(kurtosis of the square envelope spectrum,KSES)为权值,结合平方包络谱基尼系数(Gini index of the square envelope spectrum,GISES)构建加权平方包络谱基尼系数(weighted Gini index of the square envelope spectrum,WGISES)作为目标函数,通过优化算法确定FMD的最优参数组合;其次,为解决FMD的主模态分量难以选取的问题,通过计算所分解模态分量的KSES值选取主模态分量;最后,通过包络谱分析实现故障诊断。经仿真信号和实测信号分析,验证了POFMD在强背景噪声下滚动轴承故障诊断中的有效性。与变分模态分解、最大相关峭度解卷积和谱峭度相比,POFMD有更优越的故障特征提取性能。
文摘在全球变暖和人类活动的背景下,降水在年内分布上发生了比较大的变化,对人民生产生活产生了巨大的影响,这一影响在城市化较高的地区尤为明显。基于多源降水数据(降水产品数据和气象站点数据)和夜间灯光数据,选定中国的长三角城市群作为研究区域,将基尼系数(Gini Index,GI)作为降水集中度的指标,利用Theil-Sen Median斜率估计和Mann-Kendall显著性检验进行趋势分析,最后通过相关性分析探究城市化程度与降水集中度的关系。研究结果表明:(1)CHIRPS(Climate Hazards Group InfraRed Precipitation with Station Data)数据计算得到的GI与站点数据结果的均方根误差为0.036,远小于CMFD数据(0.067)和MSWEP数据(0.083)的结果,表明CHIRPS数据具有最佳的适用性;(2)长三角城市群的降水不均匀性从南向北逐渐增加,并在城市群中部和西部呈现出显著上升的趋势,研究区域内的降水年内分布将会朝着集中分布的方向发展,极端降水事件出现的可能性增加;(3)城市化对降水集中度主要起到促进作用,城市的快速发展使得降水不均匀性增强,并且在城市群内的南京市、无锡市和镇江市等地区更为显著,更有可能发生城市内涝等灾害。研究对于城市的防洪设计、城市道路排水管道的设计和城市防洪应急响应预案的编制具有参考意义。
