Incomplete multi-view clustering, which aims to solve the clustering problem on the incomplete multi-view data with partial view missing, has received more and more attention in recent years. Although numerous methods have been developed, most of the methods either cannot flexibly handle the incomplete multi-view data with arbitrary missing views or do not consider the negative factor of information imbalance among views. Moreover, some methods do not fully explore the local structure of all incomplete views. To tackle these problems, this paper proposes a simple but effective method, named localized sparse incomplete multi-view clustering (LSIMVC). Different from the existing methods, LSIMVC intends to learn a sparse and structured consensus latent representation from the incomplete multi-view data by optimizing a sparse regularized and novel graph embedded multi-view matrix factorization model. Specifically, in such a novel model based on the matrix factorization, a $l_{1}$ norm based sparse constraint is introduced to obtain the sparse low-dimensional individual representations and the sparse consensus representation. Moreover, a novel local graph embedding term is introduced to learn the structured consensus representation. Different from the existing works, our local graph embedding term aggregates the graph embedding task and consensus representation learning task into a concise term. Furthermore, to reduce the imbalance factor of incomplete multi-view learning, an adaptive weighted learning scheme is introduced to LSIMVC. Finally, an efficient optimization strategy is given to solve the optimization problem of our proposed model. Comprehensive experimental results performed on six incomplete multi-view databases verify that the performance of our LSIMVC is superior to the state-of-the-art IMC approaches. The code is available in https://github.com/justsmart/LSIMVC .

The continuous developments of urban and industrial environments have increased the demand for intelligent video surveillance. Deep learning has achieved remarkable performance for anomaly detection in surveillance videos. Previous approaches achieve anomaly detection with a single-pretext task (image reconstruction or prediction) and detect anomalies by larger reconstruction error or poor prediction. However, they cannot fully exploit the discriminative semantics and temporal context information. Moreover, tackling anomaly detection with a single pretext task is suboptimal due to the nonalignment between the pretext task and anomaly detection. In this article, we propose a temporal-aware contrastive network (TAC-Net) to address the abovementioned problems of anomaly detection for intelligence video surveillance. TAC-Net is an unsupervised method that utilizes deep contrastive self-supervised learning to capture the high-level semantic features and tackles anomaly detection with multiple self-supervised tasks. During inference phase, the multiple task losses and contrastive similarity are utilized to calculate the anomaly score. Experimental results show that our method is superior to state-of-the-art approaches on three benchmarks, which demonstrates the validity and advancement of TAC-Net.

Incomplete multiview clustering (IMC) is a hot and emerging topic. It is well known that unavoidable data incompleteness greatly weakens the effective information of multiview data. To date, existing IMC methods usually bypass unavailable views according to prior missing information, which is considered a second-best scheme based on evasion. Other methods that attempt to recover missing information are mostly applicable to specific two-view datasets. To handle these problems, in this article, we propose an information-recovery-driven-deep IMC network, termed as RecFormer. Concretely, a two-stage autoencoder network with self-attention structure is built to synchronously extract high-level semantic representations of multiple views and recover the missing data. Besides, we develop a recurrent graph reconstruction mechanism that cleverly leverages the restored views to promote representation learning and further data reconstruction. Visualization of recovery results are given and sufficient experimental results confirm that our RecFormer has obvious advantages over other top methods.

Weakly supervised object detection (WSOD) has received widespread attention since it requires only image-category annotations for detector training. Many advanced approaches solve this problem by a two-phase learning framework, that is, instance mining that classifies generated proposals via multiple instance learning, and instance refinement that iteratively refines bounding boxes using the supervision produced by the preceding stage. In this paper, we observe that the detection performance is usually limited by imprecise supervision, including part domination and untight boxes. To mitigate their adverse effects, we focus on selecting high-quality proposals as the supervision for WSOD. To be specific, for the issue of part domination, we propose bottom-up aggregated attention which incorporates low-level features from shallow layers to improve location representation of top-level features. In this manner, the proposals corresponding to entire objects can get high scores. Its advantage is that it can be flexibly plugged into the WSOD framework since there is no need to attach learnable parameters or learning branches. As regards the problem of untight boxes, we propose a phase-aware loss, which is the first work to measure supervision quality by the loss in the instance mining phase, to highlight correct boxes and suppress untight ones. In this work, we unify the proposed two modules into the framework of online instance classifier refinement. Extensive experiments on the PASCAL VOC and the MS COCO demonstrate that our method can significantly improve the performance of WSOD and achieve the state-of-the-art results. The code is available at https://github.com/Horatio9702/BUAA_PALoss.

Weakly supervised object detection (WSOD) has become an effective paradigm, which requires only class labels to train object detectors. However, WSOD detectors are prone to learn highly discriminative features corresponding to local objects rather than complete objects, resulting in imprecise object localization. To address the issue, designing backbones specifically for WSOD is a feasible solution. However, the redesigned backbone generally needs to be pretrained on large-scale ImageNet or trained from scratch, both of which require much more time and computational costs than fine-tuning. In this article, we explore to optimize the backbone without losing the availability of the original pretrained model. Since the pooling layer summarizes neighborhood features, it is crucial to spatial feature learning. In addition, it has no learnable parameters, so its modification will not change the pretrained model. Based on the above analysis, we further propose enhanced spatial feature learning (ESFL) for WSOD, which first takes full advantage of multiple kernels in a single pooling layer to handle multiscale objects and then enhances above-average activations within the rectangular neighborhood to alleviate the problem of ignoring unsalient object parts. The experimental results on the PASCAL VOC and the MS COCO benchmarks demonstrate that ESFL can bring significant performance improvement for the WSOD method and achieve state-of-the-art results.

Weakly supervised object detection (WSOD) aims to train object detectors by using only image-level annotations. Many recent works on WSOD adopt multiple instance detection networks (MIDN), which usually generate a certain number of proposals and regard proposal classification as a latent model learning within image classification. However, these methods tend to detect salient object, salient object parts and clustered objects due to lack of instance-level annotations during training. Thus a core issue is how to guarantee that the network learn as many objects with precise bounding boxes as possible. In this paper, we address this issue by exploiting the potential of proposal scores during training. We propose an adaptive instance refinement (AIR) framework with three novel designs, which can be integrated with MIDN into a single network. Specifically, adaptive instance mining attempts to discover all positive instances according to the score distribution of proposals and their spatial similarity. Adaptive score modulation dynamically adjusts proposal scores to make the network focus more on instances with different difficulties in different training iterations. Adaptive knowledge refinement distills important information from all previous stages by the weighted average of proposal scores. The experimental results on the PASCAL VOC 2007 and 2012 benchmarks and the MS COCO benchmark demonstrate that AIR significantly improves the performance of the original MIDN and achieves the state-of-the-art results.