Fig. 1

Schematic diagram of an artificial neural network (ANN). a shows a schematic diagram of a perceptron. It is the simplest model of an ANN and only includes an input layer and an output layer. In the perceptron, the input feature parameters are directly converted to the output results through the weight between the input and output. b shows a schematic diagram of a 3-layer ANN (also called a multilayer perception). The first layer is the input layer, corresponding to the input feature parameters (X); the middle is the hidden layer, which uses a composite function to achieve the abstraction for input features so that the input can be better divided linearly; the last is the output layer, where the number of categories to be classified determines the number of neurons in this layer, and its output value (Y) is the predictive value of the ANN