With the tremendous growth of mobile social networks (MSNs), people are highly relying on it to connect with friends and further expand their social circles. However, the conventional friendship inference techniques have issues handling such a large yet sparse multi-source data. The related friend recommendation systems are therefore suffering from reduced accuracy and limited scalability. To address this issue, we propose a Two-stage Deep learning framework for Friendship Inference, namely TDFI. This approach enables MSNs to exploit multi-source information simultaneously, rather than hierarchically. Therefore, there is no need to manually set which information is more important and the order in which the various information is applied. In details, we apply an Extended Adjacency Matrix (EAM) to represent the multi-source information. We then adopt an improved Deep Auto-Encoder Network (iDAEN) to extract the fused feature vector for each user. Our framework also provides an improved Deep Siamese Network (iDSN) to measure user similarity. To provide a substantial description and evaluation of the proposed methodology, we evaluate the effectiveness and robustness on three large-scale real-world datasets. Trace-driven evaluation results demonstrate that TDFI can effectively handle the sparse multi-source data while providing better accuracy for friendship inference. Through the comparison with numerous state-of-the-art methods, we find that TDFI can achieve superior performance via real-world multi-source information. Meanwhile, it demonstrates that the proposed pipeline can not only integrate structural information and attribute information, but also be compatible with different attribute information, which further enhances the overall applicability of friend-recommendation systems under information-rich MSNs.

With the explosive growth of Internet of Things (IoT) devices and various emerging network technologies, IoT-enabled smart cities are further refined into health smart cities. For example, IoT devices can automatically recognize emotional states through collected facial expressions, which can further serve mental health assessment, human–computer interaction, etc. On the other hand, existing facial expression recognition algorithms emphasize the application of deep neural networks (DNNs), and it is difficult for resource-constrained IoT devices to provide sufficient computing resources to optimize parameters for DNN-based structures. To solve the challenge of resource constraints, we propose the hierarchical emotion recognition system enabled by mobile edge computing (MEC). Specifically, MEC nodes provide IoT devices with short-delay and high-performance computing services, satisfying the requirements of training DNN-based algorithms. Moreover, our proposed emotion recognition system leverages a pretrained feature extraction module on the remote cloud to accelerate optimization and provides a localization module for specific tasks of IoT devices. In addition to evaluating the accuracy and efficiency, we also clarify that the DNN-based emotion recognition system exposes obvious vulnerability to perturbation. Due to the uncertainty of the environment, it is common for facial expressions collected by IoT devices to be accompanied by perturbation. To address this issue, we propose the proactive perturbation-aware defense mechanism. It has been demonstrated that the newly proposed defense mechanism can maintain state-of-the-art performance on the publicly available LIRIS-CSE dataset while defending against known and unknown perturbation. This can promote the deployment of our proposed MEC-enabled hierarchical emotion recognition system and defense mechanism in real-world scenarios.

Due to the explosive growth of social network services, friendship inference has been widely adopted by Online Social Service Providers (OSSPs) for friend recommendation. The conventional techniques, however, have limitations in accuracy or scalability to handle such a large yet sparse multi-source data. For example, the OSSPs will be required to manually give the order in which the various information is applied. This unavoidably reduces the applicability of existing friend recommendation systems. To address this issue, we propose a Two-stage Deep learning framework for Friendship Inference (TDFI). This approach can utilize multi-source information simultaneously with low complexity. In particular, we apply an Extended Adjacency Matrix (EAM) to represent the multi-source information. We then adopt an improved Deep AutoEncoder Network (iDAEN) to extract the fused feature vector for each user. The TDFI framework also provides an improved Deep Siamese Network (iDSN) to measure user similarity from iDAEN. Finally, we evaluate the effectiveness and robustness of TDFI on three large-scale real-world datasets. It shows that TDFI can effectively handle the sparse multi-source data while providing better accuracy for friend recommendation.

Security surveillance is critical to social harmony and people's peaceful life. It has a great impact on strengthening social stability and life safeguarding. Detecting anomaly timely, effectively and efficiently in video surveillance remains challenging. This paper proposes a new approach, called S2-VAE, for anomaly detection from video data. The S2-VAE consists of two proposed neural networks: a Stacked Fully Connected Variational AutoEncoder (SF-VAE) and a Skip Convolutional VAE (SC-VAE). The SF-VAE is a shallow generative network to obtain a model like Gaussian mixture to fit the distribution of the actual data. The SC-VAE, as a key component of S2-VAE, is a deep generative network to take advantages of CNN, VAE and skip connections. Both SF-VAE and SC-VAE are efficient and effective generative networks and they can achieve better performance for detecting both local abnormal events and global abnormal events. The proposed S2-VAE is evaluated using four public datasets. The experimental results show that the S2-VAE outperforms the state-of-the-art algorithms. The code is available publicly at https://github.com/tianwangbuaa/.