In order to establish characteristic indexes of floc structure in activated sludge, 19microscopic parameters used for description of floc structure were divided into four groups: floc size (SZ), compactness (CP), regulation (RG) and filamentous microbes (FL). These four groups included 4, 5, 8, 2indexes, respectively. Principal component analysis method (PCA, linear dimension reduction) and Isometric mapping method (Isomap, nonlinear dimension reduction) were used to reduce dimensions of these parameters of floc structure. By comparing decrease range and effectiveness of dimension reduction with two methods above, the characteristics indexes of floc structure were established. After treatment of dimension reduction with PCA, the group index of SZ, FL of floc structure can be characterized by 1comprehensive index, so can the group index FL, but for the group index CP, RG, each of them need 3comprehensive indexes to represent their characteristics. The decrease range of dimension reduction of SZ, CP, RG, FL are 0.750, 0.400, 0.625 and 0.500, respectively. The dimensionality of floc structure reduced by Isomap method can be characterized by 1comprehensive index for each group, the decrease range of dimension reduction of SZ, CP, RG, FL are 0.750, 0.800, 0.875 and 0.500, respectively. Therefore, the comprehensive indexes with Isomap dimension reduction are more accurate, concise to describe floc structure characteristics than those with PCA dimension reduction and more suitable for being characteristics indexes of floc structure in activated sludge.%为建立活性污泥絮体结构分析的特征指标,将现有描述絮体结构的19个微观参数分为4类:絮体大小(SZ)、密实度(CP)、规则度(RG)和丝状菌(FL)特征,分别含4、5、8、2个.分别采用主成分分析法(PCA,线性降维)和等距映射法(Isomap,非线性降维)对这些絮体结构特征微观参数进行降维分析,通过对两种降维法的降维幅度和降维有效性的比较,确定絮体结构特征指标.结果表明:PCA降维后絮体SZ、FL各由1个综合指标表征,而CP、RG各由3个综合指标表征,SZ、CP、RG和FL的降维幅度分别为0.750、0.400、0.625和0.500;Isomap降维后絮体SZ、CP、RG和FL均由1个综合指标表征,降维幅度分别为0.750、0.800、0.875和0.500.从降维幅度和降维有效性分析可知,Isomap降维后的综合指标更能准确、简洁地描述絮体结构特征,更适合作为活性污泥絮体结构的特征指标.
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