K-means聚类算法随机确定初始聚类数目,而且原始数据集中含有大量的冗余特征会导致聚类时精度降低,而布谷鸟搜索(CS)算法存在收敛速度慢和局部搜索能力弱等问题,为此提出一种基于自适应布谷鸟优化特征选择的K-means聚类算法(DCFSK)。首...K-means聚类算法随机确定初始聚类数目,而且原始数据集中含有大量的冗余特征会导致聚类时精度降低,而布谷鸟搜索(CS)算法存在收敛速度慢和局部搜索能力弱等问题,为此提出一种基于自适应布谷鸟优化特征选择的K-means聚类算法(DCFSK)。首先,为提升CS算法的搜索速度和精度,在莱维飞行阶段,设计了自适应步长因子;为调节CS算法全局搜索和局部搜索之间的平衡、加快CS算法的收敛,动态调整发现概率,进而提出改进的动态CS算法(IDCS),在IDCS的基础上构建了结合动态CS的特征选择算法(DCFS)。其次,为提升传统欧氏距离的计算精确度,设计同时考虑样本和特征对距离计算贡献程度的加权欧氏距离;为了确定最佳聚类数目的选取方法,依据改进的加权欧氏距离构造了加权簇内距离和簇间距离。最后,为克服传统K-means聚类目标函数仅考虑簇内的距离而未考虑簇间距离的缺陷,提出基于中位数的轮廓系数的目标函数,进而设计了DCFSK。实验结果表明,在10个基准测试函数上,IDCS的各项指标取得了较优的结果;相较于K-means、DBSCAN(Density-Based Spatial Clustering of Applications with Noise)等算法,在6个合成数据集与6个UCI数据集上,DCFSK的聚类效果最佳。展开更多
The mesoscale eddy is a typical mesoscale oceanic phenomenon that transfers ocean energy. The detection and extraction of mesoscale eddies is an important aspect of physical oceanography, and automatic mesoscale eddy ...The mesoscale eddy is a typical mesoscale oceanic phenomenon that transfers ocean energy. The detection and extraction of mesoscale eddies is an important aspect of physical oceanography, and automatic mesoscale eddy detection algorithms are the most fundamental tools for detecting and analyzing mesoscale eddies. The main data used in mesoscale eddy detection are sea level anomaly(SLA) data merged by multi-satellite altimeters' data.These data objectively describe the state of the sea surface height. The mesoscale eddy can be represented by a local equivalent region surrounded by an SLA closed contour, and the detection process requires the extraction of a stable closed contour structure from SLA maps. In consideration of the characteristics of mesoscale eddy detection based on SLA data, this paper proposes a new automatic mesoscale eddy detection algorithm based on clustering. The mesoscale eddy structure can be extracted by separating and filtering SLA data sets to separate a mesoscale eddy region and non-eddy region and then establishing relationships among eddy regions and mapping them on SLA maps. This paper overcomes the problem of the sensitivity of parameter setting that affects the traditional detection algorithm and does not require a sensitivity test. The proposed algorithm is thus more adaptable. An eddy discrimination mechanism is added to the algorithm to ensure the stability of the detected eddy structure and to improve the detection accuracy. On this basis, the paper selects the Northwest Pacific Ocean and the South China Sea to carry out a mesoscale eddy detection experiment. Experimental results show that the proposed algorithm is more efficient than the traditional algorithm and the results of the algorithm remain stable. The proposed algorithm detects not only stable single-core eddies but also stable multi-core eddy structures.展开更多
To guarantee the accuracy and real-time of the 3D reconstruction method for outdoor scene,an algorithm based on region segmentation and matching was proposed.Firstly,on the basis of morphological gradient information,...To guarantee the accuracy and real-time of the 3D reconstruction method for outdoor scene,an algorithm based on region segmentation and matching was proposed.Firstly,on the basis of morphological gradient information,obtained by comparing color weight gradient images and proposing a multi-threshold segmentation,scene contour features were extracted by a watershed algorithm and a fuzzy c-means clustering algorithm.Secondly,to reduce the search area,increase the correct matching ratio and accelerate the matching speed,the region constraint was established according to a region＇s local position,area and gray characteristics,the edge pixel constraint was established according to the epipolar constraint and the continuity constraint.Finally,by using the stereo matching edge pixel pairs,their 3D coordinates were estimated according to the binocular stereo vision imaging model.Experimental results show that the proposed method can yield a high stereo matching ratio and reconstruct a 3D scene quickly and efficiently.展开更多
针对基于差分隐私的K-means聚类存在数据效用差的问题,基于乌鸦搜索和轮廓系数提出了一个隐私保护的聚类算法(privacy preserving clustering algorithm based on crow search, CS-PCA)。该算法一方面利用轮廓系数对每次迭代中每个簇的...针对基于差分隐私的K-means聚类存在数据效用差的问题,基于乌鸦搜索和轮廓系数提出了一个隐私保护的聚类算法(privacy preserving clustering algorithm based on crow search, CS-PCA)。该算法一方面利用轮廓系数对每次迭代中每个簇的聚类效果进行评估,根据聚类效果添加不同数量的噪声,并利用聚类合并思想降低噪声对聚类的影响;另一方面利用乌鸦搜索对差分隐私的K-means隐私保护聚类算法中初始质心的选择进行优化,防止算法陷入局部最优。实验结果表明,CS-PCA算法的聚类有效性更高,并且同样适用于大规模数据。从整体上看,随着隐私预算的不断增大,CS-PCA算法的F-measure值分别比DP-KCCM和PADC算法高了0~281.3312%和4.5876%~470.3704%。在相同的隐私预算下,CS-PCA算法在绝大多数情况下聚类结果可用性优于对比算法。展开更多
文摘K-means聚类算法随机确定初始聚类数目,而且原始数据集中含有大量的冗余特征会导致聚类时精度降低,而布谷鸟搜索(CS)算法存在收敛速度慢和局部搜索能力弱等问题,为此提出一种基于自适应布谷鸟优化特征选择的K-means聚类算法(DCFSK)。首先,为提升CS算法的搜索速度和精度,在莱维飞行阶段,设计了自适应步长因子;为调节CS算法全局搜索和局部搜索之间的平衡、加快CS算法的收敛,动态调整发现概率,进而提出改进的动态CS算法(IDCS),在IDCS的基础上构建了结合动态CS的特征选择算法(DCFS)。其次,为提升传统欧氏距离的计算精确度,设计同时考虑样本和特征对距离计算贡献程度的加权欧氏距离;为了确定最佳聚类数目的选取方法,依据改进的加权欧氏距离构造了加权簇内距离和簇间距离。最后,为克服传统K-means聚类目标函数仅考虑簇内的距离而未考虑簇间距离的缺陷,提出基于中位数的轮廓系数的目标函数,进而设计了DCFSK。实验结果表明,在10个基准测试函数上,IDCS的各项指标取得了较优的结果;相较于K-means、DBSCAN(Density-Based Spatial Clustering of Applications with Noise)等算法,在6个合成数据集与6个UCI数据集上,DCFSK的聚类效果最佳。
基金The National Key R&D Program of China under contract No.2016YFC1401800the National Natural Science Foundation of China under contract No.41576176the National Programme on Global Change and Air-Sea Interaction under contract Nos GASI-02-PAC-YGST2-04,GASI-02-IND-YGST2-04 and GASI-02-SCS-YGST2-04
文摘The mesoscale eddy is a typical mesoscale oceanic phenomenon that transfers ocean energy. The detection and extraction of mesoscale eddies is an important aspect of physical oceanography, and automatic mesoscale eddy detection algorithms are the most fundamental tools for detecting and analyzing mesoscale eddies. The main data used in mesoscale eddy detection are sea level anomaly(SLA) data merged by multi-satellite altimeters' data.These data objectively describe the state of the sea surface height. The mesoscale eddy can be represented by a local equivalent region surrounded by an SLA closed contour, and the detection process requires the extraction of a stable closed contour structure from SLA maps. In consideration of the characteristics of mesoscale eddy detection based on SLA data, this paper proposes a new automatic mesoscale eddy detection algorithm based on clustering. The mesoscale eddy structure can be extracted by separating and filtering SLA data sets to separate a mesoscale eddy region and non-eddy region and then establishing relationships among eddy regions and mapping them on SLA maps. This paper overcomes the problem of the sensitivity of parameter setting that affects the traditional detection algorithm and does not require a sensitivity test. The proposed algorithm is thus more adaptable. An eddy discrimination mechanism is added to the algorithm to ensure the stability of the detected eddy structure and to improve the detection accuracy. On this basis, the paper selects the Northwest Pacific Ocean and the South China Sea to carry out a mesoscale eddy detection experiment. Experimental results show that the proposed algorithm is more efficient than the traditional algorithm and the results of the algorithm remain stable. The proposed algorithm detects not only stable single-core eddies but also stable multi-core eddy structures.
基金Supported by the Ministerial Level Advanced Research Foundation(40401060305)
文摘To guarantee the accuracy and real-time of the 3D reconstruction method for outdoor scene,an algorithm based on region segmentation and matching was proposed.Firstly,on the basis of morphological gradient information,obtained by comparing color weight gradient images and proposing a multi-threshold segmentation,scene contour features were extracted by a watershed algorithm and a fuzzy c-means clustering algorithm.Secondly,to reduce the search area,increase the correct matching ratio and accelerate the matching speed,the region constraint was established according to a region＇s local position,area and gray characteristics,the edge pixel constraint was established according to the epipolar constraint and the continuity constraint.Finally,by using the stereo matching edge pixel pairs,their 3D coordinates were estimated according to the binocular stereo vision imaging model.Experimental results show that the proposed method can yield a high stereo matching ratio and reconstruct a 3D scene quickly and efficiently.
文摘针对基于差分隐私的K-means聚类存在数据效用差的问题,基于乌鸦搜索和轮廓系数提出了一个隐私保护的聚类算法(privacy preserving clustering algorithm based on crow search, CS-PCA)。该算法一方面利用轮廓系数对每次迭代中每个簇的聚类效果进行评估,根据聚类效果添加不同数量的噪声,并利用聚类合并思想降低噪声对聚类的影响;另一方面利用乌鸦搜索对差分隐私的K-means隐私保护聚类算法中初始质心的选择进行优化,防止算法陷入局部最优。实验结果表明,CS-PCA算法的聚类有效性更高,并且同样适用于大规模数据。从整体上看,随着隐私预算的不断增大,CS-PCA算法的F-measure值分别比DP-KCCM和PADC算法高了0~281.3312%和4.5876%~470.3704%。在相同的隐私预算下,CS-PCA算法在绝大多数情况下聚类结果可用性优于对比算法。
