Nitrogen oxide (NOx) is one of the main pollutants in the regenerated flue gas of Fluid Catalytic Cracking (FCC) unit. Accurate prediction of NOx emission can effectively avoid the occurrence of pollution events in refinery enterprises. Because of the non-stationarity, nonlinearity and long-memory characteristics of pollutant emission data, a new hybrid model incorporating Ensemble Empirical Mode Decomposition (EEMD) and Long Short-Term Memory network (LSTM) was proposed to improve the prediction accuracy of pollutant emission concentration. The NOx emission concentration data was first decomposed into several Intrinsic Mode Functions (IMFs) and a residual by using the EEMD model. According to the correlation analysis between the IMF sub-sequences and the original data, the IMF sub-sequences with low correlation were eliminated, which could effectively reduce the noise in the original data. The IMFs could be divided into high and low frequency sequences, which were respectively trained in the LSTM networks with different depths. The final NOx concentration prediction results were reconstructed by the predicted results of each sub-sequences. Compared with the performance of LSTM in the NOx emission prediction of FCC unit, the Mean Square Error (MSE), Mean Absolute Error (MAE) were reduced by 46.7%, 45.9%,and determination coefficient (R2) of EEMD-LSTM was improved by 43% respectively, which means the proposed model achieves higher prediction accuracy.
Moving object detection and static map reconstruction in the environment with complex dynamic background are prone to incomplete moving object detection. In order to solve the problem, a new moving object detection method with hybrid vision system assisted by point cloud segmentation was proposed. Firstly, the PassThrough+RANdom SAmple Consensus (RANSAC) method was proposed to overcome large-area wall interference, so as to realize the point cloud ground point recognition. Secondly, the non-ground point data were projected to the image as feature points, and their optical flow motion vectors and artificial motion vectors were estimated to detect the dynamic points. Then, the dynamic threshold strategy was used to perform Euclidean clustering to the point cloud. Finally, the results of dynamic point detection and point cloud segmentation were integrated to completely extract the moving objects. In addition, the Octomap tool was used to convert the point cloud map into a 3D grid map in order to complete the map construction. Through the experimental results and data analysis, it can be seen that the proposed method can effectively improve the integrity of moving object detection, and reconstruct a low-loss, highly-practical static grid map.
Concerning the influence of resident's psychological factors on travel mode choice in the actual travel, a travel mode choice model based on prospect theory was established and a choice method more according to human thinking habits was put forward. Considering psychological reference points of travel time and travel cost comprehensively, satisfied travel mode to resident was obtained. The influence of reference point on travel mode was analyzed by comparing changes of comprehensive prospect value under different reference points. Finally an example gave the application of this travel mode choice method. The experimental results show that residents in the minority whose expectation of travel time is lower prefer bus travel, although the comprehensive prospect value changes of taxi and private car are identical. More residents tend to use private car mode, which is consistent with the fact. The proposed method provides a new way to predict resident travel mode.