Recurrent Neural Networks and classical machine learning methods for concentrations prediction of aluminum alloy in Laser Induced Breakdown Spectroscopy

Recurrent Neural Networks are classes of Artificial Neural Networks that establish connections between various nodes in a directed or undirected graph for investigation of the temporal dynamical. In this study, different Recurrent Neural Network (RNN) architectures are utilized for quantitative analysis of aluminum alloys by the laser induced breakdown spectroscopy (LIBS) technique. The fundamental harmonic (1064nm) of a nanosecond Nd:YAG laser pulse is employed to generate the LIBS plasma for the prediction of constituent concentrations of the aluminum standard samples. For the purpose of predicting concentration, Recurrent Neural Networks based on different networks, such as Long Short Term Memory (LSTM), Gated Recurrent Unit (GRU), Simple Recurrent Neural Network (Simple RNN), and as well as Recurrent Convolutional Networks comprising of Conv-SimpleRNN, Conv-LSTM and Conv-GRU are employed. Then, a comparison is made among prediction by classical machine learning methods of support vector regressor (SVR), the Multilayer Perceptron (MLP), Decision Tree algorithm, Gradient Boosting Regression (GBR), Random Forest Regression (RFR), Linear Regression, and k-Nearest Neighbor (KNN) algorithm. Results demonstrated that the machine learning tools based on Convolutional Recurrent Networks had the best efficiencies in prediction of the most of the elements among other multivariate methods.