Aiming at the correlation problem between sleep stages and sleep apnea hypopnea, a sleep physiological time series classification method based on adaptive multi-task learning was proposed. Single-channel electroencephalogram and electrocardiogram were used for sleep staging and Sleep Apnea Hypopnea Syndrome (SAHS) detection. A two-stream time dependence learning module was utilized to extract shared features under joint supervision of the two tasks. The correlation between sleep stages and sleep apnea hypopnea was modeled by the adaptive inter-task correlation learning module with channel attention mechanism. The experimental results on two public datasets indicate that the proposed method can complete sleep staging and SAHS detection simultaneously. On UCD dataset, the accuracy, MF1(Macro F1-score), and Area Under the receiver characteristic Curve (AUC) for sleep staging of the proposed method were 1.21 percentage points, 1.22 percentage points, and 0.008 3 higher than those of TinySleepNet; its MF2 (Macro F2-score), AUC, and recall of SAHS detection were 11.08 percentage points, 0.053 7, and 15.75 percentage points higher than those of the 6-layer CNN model, which meant more disease segments could be detected. The proposed method could be applied to home sleep monitoring or mobile medical to achieve efficient and convenient sleep quality assessment, assisting doctors in preliminary diagnosis of SAHS.
With the development of Artificial Intelligence (AI) technology, the Deep Neural Network (DNN) models have been applied to various mobile and edge devices widely. However, the model deployment becomes challenging and the popularization and application of the models are limited due to the facts that the computing power of edge devices is low, the memory capacity of edge devices is small, and the realization of model acceleration requires in-depth knowledge of edge device hardware. Therefore, a DNN acceleration and deployment method based on Tensor Virtual Machine (TVM) was presented to accelerate the Convolutional Neural Network (CNN) model on Field-Programmable Gate Array (FPGA), and the feasibility of this method was verified in the application scenarios of distracted driving classification. Specifically, in the proposed method, the computational graph optimization method was utilized to reduce the memory access and computational overhead of the model, the model quantization method was used to reduce the model size, and the computational graph packing method was adopted to offload the convolution calculation to the FPGA in order to speed up the model inference. Compared with MPU (MicroProcessor Unit), the proposed method can reduce the inference time of ResNet50 and ResNet18 on MPU+FPGA by 88.63% and 77.53% respectively. On AUC (American University in Cairo) dataset, compared to MPU, the top1 inference accuracies of the two models on MPU+FPGA are only reduced by 0.26 and 0.16 percentage points respectively. It can be seen that the proposed method can reduce the deployment difficulty of different models on FPGA.
Accurate prediction of taxi demands between urban regions can provide decision support information for taxi guidance and scheduling as well as passenger travel recommendation, so as to optimize the relation between taxi supply and demand. However, most of the existing models only focus on modeling and predicting the taxi demands within a region, do not consider enough the spatial-temporal correlation between regions, and pay less attention to the more fine-grained demand prediction between regions. To solve the above problems, a prediction model for taxi demands between urban regions — Origin-Destination fusion with Spatial-Temporal Network (ODSTN) model was proposed. In this model, complex spatial-temporal correlations between regions was captured from spatial dimensions of the regions and region pairs respectively and three temporal dimensions of recent, daily and weekly periods by using graph convolution and attention mechanism, and a new path perception fusion mechanism was designed to combine the multi-angle features and finally realize the taxi demand prediction between urban regions. Experiments were carried out on two real taxi order datasets in Chengdu and Manhattan. The results show that the Mean Absolute Error (MAE), Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) of ODSTN model are 0.897 1, 3.527 4, 50.655 6% and 0.589 6, 1.163 8, 61.079 4%, respectively, indicating that ODSTN model has high accuracy in taxi demand prediction tasks.
The complex structure and diverse imformation of stock markets make stock movement prediction extremely challenging. However, most of the existing studies treat each stock as an individual or use graph structures to model complex higher-order relationships in stock markets, without considering the hierarchy and dynamics among stocks, industries and markets. Aiming at the above problems, a Dynamic Macro Memory Network (DMMN) was proposed, and price movement prediction was performed for multiple stocks simultaneously based on DMMN. In this method, the market macro-environmental information was modeled by the hierarchies of “stock-industry-market”, and long-term dependences of this information on time series were captured. Then, the market macro-environmental information was integrated with stock micro-characteristic information dynamically to enhance the ability of each stock to perceive the overall state of the market and capture the interdependences among stocks, industries, and markets indirectly. Experimental results on the collected CSI300 dataset show that compared with stock prediction methods based on Attentive Long Short-Term Memory (ALSTM) network, GCN-LSTM (Graph Convolutional Network with Long Short-Term Memory), Convolutional Neural Network (CNN) and other models, the DMMN-based method achieves better results in F1-score and Sharpe ratio, which are improved by 4.87% and 31.90% respectively compared with ALSTM, the best model among all comparison methods. This indicates that DMMN has better prediction performance and better practicability.
Traffic flow forecasting is an important research topic for the intelligent transportation system, however, this research is very challenging because of the complex local spatio-temporal relationships among traffic objects such as stations and sensors. Although some previous studies have made great progress by transforming the traffic flow forecasting problem into a spatio-temporal graph forecasting problem, in which the direct correlations across spatio-temporal dimensions among traffic objects are ignored. At present, there is still lack of a comprehensive modeling approach for the local spatio-temporal relationships. A novel spatio-temporal hypergraph modeling scheme was first proposed to address this problem by constructing a kind of spatio-temporal hyper-relationships to comprehensively model the complex local spatio-temporal relationships. Then, a Spatio-Temporal Hyper-Relationship Graph Convolutional Network (STHGCN) forecasting model was proposed to capture these relationships for traffic flow forecasting. Extensive comparative experiments were conducted on four public traffic datasets. Experimental results show that compared with the spatio-temporal forecasting models such as Attention based Spatial-Temporal Graph Convolutional Network (ASTGCN) and Spatial-Temporal Synchronous Graph Convolutional Network (STSGCN), STHGCN achieves better results in Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE); and the comparison of the running time of different models also shows that STHGCN has higher inference speed.
In order to overcome the problems of low convergence precision and easily relapsing into local optimum in Fruit fly Optimization Algorithm (FOA), by introducing the Levy flight strategy into the FOA, an improved FOA called double subgroups FOA with the characteristics of Levy flight (LFOA) was proposed. Firstly, the fruit fly group was dynamically divided into two subgroups (advanced subgroup and drawback subgroup) whose centers separately were the best individual and the worst individual in contemporary group according to its own evolutionary level. Secondly, a global search was made for drawback subgroup with the guidance of the best individual, and a finely local search was made for advanced subgroup by doing Levy flight around the best individual, so that not only both the global and local search ability balanced, but also the occasionally long distance jump of Levy flight could be used to help the fruit fly jump out of local optimum. Finally, two subgroups exchange information by updating the overall optimum and recombining the subgroups. The experiment results of 6 typical functions show that the new method has the advantages of better global searching ability, faster convergence and more precise convergence.
Concerning the contradiction between edge-preserving and noise-suppressing in the process of image denoising, a patch similarity anisotropic diffusion algorithm based on variable exponent for image denoising was proposed. The algorithm combined adaptive Perona-Malik (PM) model based on variable exponent for image denoising and the idea of patch similarity, constructed a new edge indicator and a new diffusion coefficient function. The traditional anisotropic diffusion algorithms for image denoising based on the intensity similarity of each single pixel (or gradient information) to detect edge cannot effectively preserve weak edges and details such as texture. However, the proposed algorithm can preserve more detail information while removing the noise, since the algorithm utilizes the intensity similarity of neighbor pixels. The simulation results show that, compared with the traditional image denoising algorithms based on Partial Differential Equation (PDE), the proposed algorithm improves Signal-to-Noise ratio (SNR) and Peak-Signal-to-Noise Ratio (PSNR) to 16.602480dB and 31.284672dB respectively, and enhances anti-noise capability. At the same time, the filtered image preserves more detail features such as weak edges and textures and has good visual effects. Therefore, the algorithm achieves a good balance between noise reduction and edge maintenance.