Internet of Things (IoT) is a network that connects things in a special union. It embeds a physical entity through an intelligent perception system to obtain information about the component at any time. It connects various objects. IoT has the ability of information transmission, information perception, and information processing. The air quality forecasting has always been an urgent problem, which affects people's quality of life seriously. So far, many air quality prediction algorithms have been proposed, which can be mainly classified into two categories. One is regression-based prediction, the other is deep learning-based prediction. Regression-based prediction is aimed to make use of the classical regression algorithm and the various supervised meteorological characteristics to regress the meteorological value. Deep learning methods usually use convolutional neural networks (CNN) or recurrent neural networks (RNN) to predict the meteorological value. As an excellent feature extractor, CNN has achieved good performance in many scenes. In the same way, as an efficient network for orderly data processing, RNN has also achieved good results. However, few or none of the above methods can meet the current accuracy requirements on prediction. Moreover, there is no way to pay attention to the trend monitoring of air quality data. For the sake of accurate results, this paper proposes a novel predicted-trend-based loss function (PTB), which is used to replace the loss function in RNN. At the same time, the trend of change and the predicted value are constrained to obtain more accurate prediction results of PM 2.5 . In addition, this paper extends the model scenario to the prediction of the whole existing training data features. All the data on the next day of the model is mixed labels, which effectively realizes the prediction of all features. The experiments show that the loss function proposed in this paper is effective.
On the base of BP network introducing second order momentum term, this paper proposed a modified method of setting second order momentum factor. This method exploited full advantage of adding first order momentum term, and set plus-minus of second order momentum factor according to different situations of BP network on the error surface during training process. At the end of the paper, simulation experiments were made on BP network applying the new method by solving three benchmark problems: XOR, 3-Bit Parity and function approximation. The results of the experiments show that the new BP network has faster training speed and better training effect.
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