A Tensor Approach to Learning Mixed Membership Community Models

Community detection is the task of detecting hidden communities from observed interactions. Guaranteed community detection has so far been mostly limited to models with non-overlapping communities such as the stochastic block model. In this paper, we remove this restriction, and provide guaranteed community detection for a family of probabilistic network models with overlapping communities, termed as the mixed membership Dirichlet model, first introduced by Airoldi et al. This model allows for nodes to have fractional memberships in multiple communities and assumes that the community memberships are drawn from a Dirichlet distribution. Moreover, it contains the stochastic block model as a special case. We propose a unified approach to learning these models via a tensor spectral decomposition method. Our estimator is based on low-order moment tensor of the observed network, consisting of 3-star counts. Our learning method is fast and is based on simple linear algebraic operations, e.g. singular value decomposition and tensor power iterations. We provide guaranteed recovery of community memberships and model parameters and present a careful finite sample analysis of our learning method. As an important special case, our results match the best known scaling requirements for the (homogeneous) stochastic block model

A Novel Approach for Detecting Anomalous Energy Consumption Based on Micro-Moments and Deep Neural Networks

Nowadays, analyzing, detecting, and visualizing abnormal power consumption behavior of householders are among the principal challenges in identifying ways to reduce power consumption. This paper introduces a new solution to detect energy consumption anomalies based on extracting micro-moment features using a rule-based model. The latter is used to draw out load characteristics using daily intent-driven moments of user consumption actions. Besides micro-moment features extraction, we also experiment with a deep neural network architecture for efficient abnormality detection and classification. In the following, a novel anomaly visualization technique is introduced that is based on a scatter representation of the micro-moment classes, and hence providing consumers an easy solution to understand their abnormal behavior. Moreover, in order to validate the proposed system, a new energy consumption dataset at appliance level is also designed through a measurement campaign carried out at Qatar University Energy Lab, namely, Qatar University dataset. Experimental results on simulated and real datasets collected at two regions, which have extremely different climate conditions, confirm that the proposed deep micro-moment architecture outperforms other machine learning algorithms and can effectively detect anomalous patterns. For example, 99.58% accuracy and 97.85% F1 score have been achieved under Qatar University dataset. These promising results establish the efficacy of the proposed deep micro-moment solution for detecting abnormal energy consumption, promoting energy efficiency behaviors, and reducing wasted energy. 2020, The Author(s).Open Access funding provided by the Qatar National Library. This paper was made possible by National Priorities Research Program (NPRP) grant No. 10-0130-170288 from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Towards Segment-level Video Understanding: Detecting Activities from Untrimmed Videos

We generate massive amounts of video data every day. While most real-world videos are long and untrimmed with sparsely localized segments of interest, existing AI systems that can interpret videos today often rely on static image analysis or can only process temporal information in a short video snippet. To automatically understand the content of long video streams, this thesis mainly describes the efforts to design accurate, efficient, and intelligent deep learning algorithms for temporal activity detection in untrimmed videos. Detecting segments of interest from untrimmed videos is a key step towards segment-level video understanding. Depending on the purposes of tasks being performed, we address three different activity detection tasks: detecting activities of interest from videos without specific purposes (i.e., temporal activity detection); detecting temporal segment that best corresponds to a language query (i.e., natural language moment retrieval); and detecting activities given less supervision (i.e., weakly-supervised or few-shot activity detection).In temporal activity detection, We first propose a highly unified single-shot temporal activity detector based on fully 3D convolutional networks, by eliminating explicit temporal proposal and classification stages. Evaluations show that it achieves state-of-the-art on temporal activity detection while being super efficient to operate at 1271 FPS. We then investigate how to effectively apply a multi-scale architecture to model activities with various temporal length and frequency. We propose three novel architecture designs: (1) dynamic temporal sampling; (2) two-branch feature hierarchy; (3) multi-scale contextual feature fusion, and we combine all these components into a uniform network and achieve the state-of-the-art on a much larger temporal activity detection benchmark.In natural language moment retrieval, we aim to localize the segment that best corresponds to a given language query. We present a language-guided temporal attention module and an iterative graph adjustment network to handle the semantic and structural misalignment between video and language. The proposed model demonstrates superior capability to handle temporal relations, thus, significantly improves the state-of-the-art by a large margin.Finally, we study the problem of weakly-supervised and few-shot temporal activity detection to mitigate the drawbacks of huge amounts of supervision needed to train a temporal detection model. Namely, we answer the question if we can learn a temporal activity detector under weak supervision that is able to localize unseen activity classes. A novel meta-learning based detection method is accordingly proposed by adopting the few-shot learning technique of Relation Network. Results show that our method achieves performance superior or competitive to state-of-the-art approaches with stronger supervision.In summary, we propose a suite of algorithms and solutions to automatically detect segments of interest in long untrimmed videos. We hope our studies could provide insights for researchers to explore new deep learning paradigms for future computer vision research, especially on video-related topics

Automatically detecting important moments from everyday life using a mobile device

This paper proposes a new method to detect important moments in our lives. Our work is motivated by the increase in the quantity of multimedia data, such as videos and photos, which are capturing life experiences into personal archives. Even though such media-rich data suggests visual processing to identify important moments, the oft-mentioned problem of the semantic gap means that users cannot automatically identify or retrieve important moments using visual processing techniques alone. Our approach utilises on-board sensors from mobile devices to automatically identify important moments, as they are happening