“…Therefore, in order to combine multiple features and break the dimension limitation, amounts of machine learning algorithms have been modified and applied to the feature-based detection [10-12, 14-15, 20-23]. Thereinto, some algorithms only use the normal samples to train the decision region, such as the one-class support vector machine (OCSVM) learning algorithm [20], the isolation forest (iForest) learning algorithm [15], the local outlier factor (LOF) learning algorithm [15], the local distance-based outlier factor (LDOF) learning algorithm [21], the enhanced local sparsity coefficient (ELSC) learning algorithm [22]. And some algorithms, such as the K-nearest neighbour (KNN) learning algorithm [14], and the fast principal component analysis (PCA) learning algorithm [23].…”