For pursuing accurate skeleton-based action recognition, most prior methods use the strategy of combining Graph Convolution Networks (GCNs) with attention-based methods in a serial way. However, they regard the human skeleton as a complete graph, resulting in less variations between different actions (e.g., the connection between the elbow and head in action “clapping hands”). For this, we propose a novel Contrastive GCN-Transformer Network (ConGT) which fuses the spatial and temporal modules in a parallel way. The ConGT involves two parallel streams: Spatial-Temporal Graph Convolution stream (STG) and Spatial-Temporal Transformer stream (STT). The STG is designed to obtain action representations maintaining the natural topology structure of the human skeleton. The STT is devised to acquire action representations containing the global relationships among joints. Since the action representations produced from these two streams contain different characteristics, and each of them knows little information of the other, we introduce the contrastive learning paradigm to guide their output representations of the same sample to be as close as possible in a self-supervised manner. Through the contrastive learning, they can learn information from each other to enrich the action features by maximizing the mutual information between the two types of action representations. To further improve action recognition accuracy, we introduce the Cyclical Focal Loss (CFL) which can focus on confident training samples in early training epochs, with an increasing focus on hard samples during the middle epochs. We conduct experiments on three benchmark datasets, which demonstrate that our model achieves state-of-the-art performance in action recognition.

Graph convolutional networks (GCNs) have achieved encouraging progress in modeling human body skeletons as spatial–temporal graphs. However, existing methods still suffer from two inherent drawbacks. Firstly, these models process the input data based on the physical structure of the human body, which leads to some latent correlations among joints being ignored. Furthermore, the key temporal relationships between nonadjacent frames are overlooked, preventing to fully learn the changes of the body joints along the temporal dimension. To address these issues, we propose an innovative spatial–temporal model by introducing a self-adaptive GCN (SAGCN) with global attention network, collectively termed SAGGAN. Specifically, the SAGCN module is proposed to construct two additional dynamic topological graphs to learn the common characteristics of all data and represent a unique pattern for each sample, respectively. Meanwhile, the global attention module (spatial attention (SA) and temporal attention (TA) modules) is designed to extract the global connections between different joints in a single frame and model temporal relationships between adjacent and nonadjacent frames in temporal sequences. In this manner, our network can capture richer features of actions for accurate action recognition and overcome the defect of the standard graph convolution. Extensive experiments on three benchmark datasets (NTU-60, NTU-120, and Kinetics) have demonstrated the superiority of our proposed method.

Safety evacuation signs (SESs), as a form of environmental information and perceptual access, play an important role in promoting wayfinding and route selection by providing guidance, warning, and mandatory message to people. This study proposes an innovative crowd simulation method guided by SESs for use in emergencies. The method utilizes the syncretic virtual-real strategy by incorporating the indication function of SESs in the real world into a corresponding virtual environment. Given a virtual scene built on its real reference, our method can determine feasible and efficient routes, and produce diversified and conflict-avoiding crowd movement. Our overall solution can be applied to a variety of virtual environmental applications, whether large outdoor scenes or indoor buildings. We use extensive simulations to highlight the potential of our method in different scenarios and evaluate the results in terms of evacuation efficiency and the reasonableness of SES placement. In practice, our system runs at interactive rates and can solve complex planning problems involving one or more groups.

Medical image segmentation provides a reliable basis for diagnosis analysis and disease treatment by capturing the global and local features of the target region. To learn global features, convolutional neural networks are replaced with pure transformers, or transformer layers are stacked at the deepest layers of convolutional neural networks. Nevertheless, they are deficient in exploring local-global cues at each scale and the interaction among consensual regions in multiple scales, hindering the learning about the changes in size, shape, and position of target objects. To cope with these defects, we propose a novel Intra and Inter Attention with Mutual Consistency Learning Network (IIAM). Concretely, we design an intra attention module to aggregate the CNN-based local features and transformer-based global information on each scale. In addition, to capture the interaction among consensual regions in multiple scales, we devise an inter attention module to explore the cross-scale dependency of the object and its surroundings. Moreover, to reduce the impact of blurred regions in medical images on the final segmentation results, we introduce multiple decoders to estimate the model uncertainty, where we adopt a mutual consistency learning strategy to minimize the output discrepancy during the end-to-end training and weight the outputs of the three decoders as the final segmentation result. Extensive experiments on three benchmark datasets verify the efficacy of our method and demonstrate superior performance of our model to state-of-the-art techniques.