Underwater images, often affected by light attenuation and particle scattering, pose a challenge for restoration, aggravated by the difficulty in obtaining a substantial amount of annotated data. Existing methods have tackled this issue through the development of semi-supervised frameworks; however, they commonly lack a suitable strategy or rely on additional models trained on extra data to ensure the quality of pseudo-labels. To address this, we propose a self-assessment training framework for semi-supervised underwater image restoration (SAT-UIR). SAT-UIR employs a dual-task network (DT-Net) incorporating an auxiliary assessment task to align the restored image with a target structure similarity index measure score. This enables accurate restoration completeness estimation at a feature level and effective pseudo-label filtering during self-training. Leveraging multi-scale features, the assessment task also encourages the model to learn advantageous features for image restoration. Moreover, we integrate a soft ranking loss to further refine the training process of the auxiliary assessment task. Comprehensive experiments on various underwater benchmarks demonstrate that SAT-UIR outperforms state-of-the-art methods quantitatively and qualitatively. The code is available at https://github.com/aroid721/SAT-UIR.

Semi-supervised learning (SSL) enhances model generalizability by jointly leveraging labeled and unlabeled data. Nevertheless, the closed-world assumption of SSL always fails in open-world scenarios, where unlabeled data often contains novel classes. To address this limitation, open-world SSL (OWSSL) has been proposed as a more realistic paradigm, aiming not only to recognize known classes but also to discover novel classes. Existing OWSSL methods typically rely on representation similarity and pseudo-labeling to discriminate classes. However, during model training, these methods neglect the inherent class-prediction bias, consequently leading to self-reinforcing confirmation bias in pseudo-labels and representation confusion for hard novel classes. To address these critical challenges, we propose a Open-world Bias-guided Pseudo-label Refinement approach, named OpenBPR, which is the first to regard class prediction bias as the reference to guide the debiased pseudo-labeling and class representation decoupling. In OpenBPR, we propose a debiased pseudo-labeling method based on expectation-maximization, which exploits class prediction bias to dynamically optimize pseudo-labels, effectively alleviating confirmation bias in pseudo-labels. Furthermore, we propose a class-aware representation decoupling strategy for hard novel classes, which decouples representations by the designed competitive class decoupling regularization to assist in improving the refinement performance of pseudo-labels. Experimental results on a series of benchmark datasets demonstrate that OpenBPR outperforms state-of-the-art methods in discriminating both known and novel classes.

Diffusion models (DMs) embark a new era of generative modeling and offer more opportunities for efficient generating high-quality and realistic data samples. However, their widespread use has also brought forth new challenges in model security, which motivates the creation of more effective adversarial attackers on DMs to understand its vulnerability. We propose CAAT, a simple but generic and efficient approach that does not require costly training to effectively fool latent diffusion models (LDMs). The approach is based on the observation that cross-attention layers exhibits higher sensitivity to gradient change, allowing for leveraging subtle perturbations on published images to significantly corrupt the generated images. We show that a subtle perturbation on an image can significantly impact the cross-attention layers, thus changing the mapping between text and image during the fine-tuning of customized diffusion models. Extensive experiments demonstrate that CAAT is compatible with diverse diffusion models and out-performs baseline attack methods in a more effective (more noise) and efficient (twice as fast as Anti-DreamBooth and Mist) manner.

We consider the problem of real-time log anomaly detection for distributed system with deep neural networks by unsupervised learning. There are two challenges in this problem, including detection accuracy and analysis efficacy. To tackle these two challenges, we propose GLAD, a simple yet effective approach mining for anomalies in distributed systems. To ensure detection accuracy, we exploit the gradient features in a well-calibrated deep neural network and analyze anomalous pattern within log files. To improve the analysis efficacy, we further integrate one-class support vector machine (SVM) into anomalous analysis, which significantly reduces the cost of anomaly decision boundary delineation. This effective integration successfully solves both accuracy and efficacy in real-time log anomaly detection. Also, since anomalous analysis is based upon unsupervised learning, it significantly reduces the extra data labeling cost. We conduct a series of experiments to justify that GLAD has the best comprehensive performance balanced between accuracy and efficiency, which implies the advantage in tackling practical problems. The results also reveal that GLAD enables effective anomaly mining and consistently outperforms state-of-the-art methods on both recall and F1 scores.

Despite the astounding progress made in semi-supervised learning (SSL) and imbalanced supervised learning (ISL), there has been little attention devoted to the research of imbalanced semi-supervised learning (ISSL). The ‘Matthew effect’, a phenomenon where a disparity in data representation becomes more severe in a class-imbalanced dataset during training, could be amplified in a semi-supervised setting. In this study, we addressed two key challenges in ISSL: maintaining the reliability of pseudo-labels and ensuring a balanced representation of features. Specifically, we propose a class-aware feature-diffusion constraint and reliable pseudo-labeling (DCRP) framework to address these issues. In the DCRP, we counteract the overconfidence problem of softmax by adding an extra class to the typical K class problem without the need for additional parameters. Moreover, we introduced a flexible class-aware feature diffusion constraint in the feature extractor, promoting a more balanced feature diversity. Experimental validations on various datasets, such as CIFAR10-LT, CIFAR100-LT, SVHN-LT, and Small ImageNet-127, demonstrated consistent improvements in accuracy with our DCRP method. In particular, we achieved a steady improvement in accuracy of approximately 1% under the newly published ACR prototype across most settings. The code is available athttps://github.com/guoxiaoyuatbjtu/DCRP.

Currently, there are several handwriting recognition models available that effectively address the challenge of Handwritten Text Recognition (HTR). However, majority of tasks require downstream training tailored for specific handwritten datasets. Relying solely on the foundation model may lead to subpar recognition performance. This problem is also encountered in Manchu handwritten text recognition. To overcome this challenge, researchers have been exploring different methods, such as data augmentation through image transformations. However, the existing fine-tuning datasets do not provide sufficient coverage of characters, which can result in weaker feature extraction and limit the improvement of the model. Additionally, creating a large-scale Manchu handwritten dataset is cost-prohibitive and challenging. In light of these constraints, we propose a novel approach that involves training a foundation model using existing large-scale datasets. This is achieved by freezing certain feature layers and conducting probing with the specific characteristics of Manchu handwritten scripts. This approach aims to enrich character features and improve diverse feature extraction capabilities of the model, which can enhance the generalization capabilities of the model to small-scale Manchu handwritten datasets. The experimental results demonstrate that our probing strategy achieves superior performance compared to the state-of-the-art AMRE foundation model. Furthermore, we conducted an ablation study and additional analyses to examine the effectiveness of the probing approach and uncover the underlying modeling patterns.

Logs are valuable resources that record the health status of systems. Analyzing logs to uncover and investigate abnormal behaviors has become an essential approach of ensuring system security. However, some potential anomalies may be missed when performing log anomaly detection, and even a seemingly insignificant abnormal behavior can lead to a series of severe anomalies or continuous negative impact on the performance of systems. Therefore, the reliability and security of systems are facing significant challenges. To address this issue, in this study, we propose TransFlowLog, an Encoder-Decoder architecture-based approach for log anomaly detection. It utilizes the Transformer Encoder, a state-of-the-art sequence modeling technique, to comprehensively understand contextual relationships using self-attention mechanism. Moreover, we introduce the Interflow Decoder, which considers information exchange between channels in embedded log sequences. The Interflow Decoder enhances the features encoded by the Transformer Encoder in both sequence and channel dimensions, thereby capturing interdependence between different channels. Comparative experiments conducted on three real-world datasets demonstrate the effectiveness of the proposed method, as it achieves higher F1-score and reduces the number of false negatives.

The recently proposed class-imbalanced semi-supervised learning (CISSL) algorithms achieved impressive performance by effectively leveraging unlabeled data. However, these algorithms often rely on a pre-defined fixed confidence threshold to filter unlabeled data during training, which overlooks the varying learning dynamics across different classes in class-imbalanced scenarios. Consequently, valuable data could be discarded, leading to degraded performance on minority classes. To tackle this issue, we introduce a novel method called Class-Adaptive Threshold (CAT), which dynamically defines and adjusts the confidence threshold based on the learning status of each class. The core idea of CAT is to iteratively update the thresholds for different classes at each time step, enabling us to fully exploit valuable information that would otherwise be ignored using fixed threshold algorithms. Importantly, CAT does not introduce any additional inference processes. In our experiments, the proposed algorithm achieves state-of-the-art performance on various class-imbalanced datasets. Furthermore, we show that CAT can be seamlessly integrated into the renowned CISSL algorithm, resulting in a remarkable boost in their performance.

With the rise of Foundation models, Text-to-Image models, as one of its important branches, have been increasingly applied. While focusing on the impressive generation capabilities of these models, it is also crucial to pay attention to the robustness of the models against attacks. In this paper, we shift our focus towards studying the vulnerability of Text-to-Image (T2I) models. To this end, we propose a black-box attack method and demonstrate that T2I models are susceptible to adversarial text attacks. Specifically, this method can disrupt T2I models by making subtle modifications to the model’s input (i.e., prompt) without accessing the model parameters, resulting in the generation of incorrect images. It is worth mentioning that we discovered the ability to switch different types of tokenizers within this black-box framework to handle text, furthermore, this attack framework can be applied to target different versions of T2I models. The experiments indicate that the images generated through adversarial text exhibit noticeable errors. We also employ CLIP score, a metric used to evaluate the similarity between images and image descriptions, to assess the results. The findings demonstrate a significant decrease in the visual-textual similarity after the model is subjected to attacks. Additionally, we have identified a specific type of error that T2I models tend to make when facing attacks – when confronted with unrecognizable text, the model often interprets it as human-related content. This paper not only highlights the vulnerability of T2I models to adversarial text attacks but also further discusses potential methods that could enhance the robustness of these attack techniques. This provides a valuable reference for future research directions in this field.

Out-of-distribution detection is critical to a reliable application of deep neural networks. To reduce model uncertainty, we propose a simple yet effective approach of ensemble knowledge distillation. We blend ensemble model and knowledge distillation to improve model generalization on indomain recognition, thereby yielding accurate and robust out-of-distribution detection. The former effectively expands data recognition feature space, while the latter further regularizes the model through knowledge distillation, enhancing in-domain feature recognition. This effective integration successfully yields lower model uncertainty on in-domain feature recognition and improves anomaly detection in a more scalable manner. We justify our approach through extensive experiments on various benchmarks, demonstrating its significant improvement in out- of-distribution detection. We validate our approach with a variety of up-to-date DNNs, like Vision Transformer.

Forecasting crowd movement accurately across an urban area is crucial for efficient traffic control and ensuring public security. Current methods involve transforming the city’s roadmap into a grid-based map, enabling Convolutional Neural Networks (CNNs) or Graph Convolutional Networks (GCNs) to capture spatio-temporal relationships efficiently. However, this approach overlooks the connection between irregularly shaped real-world areas, which can be categorized into various functional zones. In this article, we introduce a novel approach for predicting urban crowd flow named STHGN, which utilizes hypergraph convolutional networks. By constructing 3-level hypergraphs from irregular areas and adopting Hyper-GCN, we capture mobility among irregular regions. We construct the hypergraphs based on hour, day, and week, simultaneously using gated-based mechanisms to fuse various embeddings. We evaluate the efficacy of our model by contrasting it with 11 other approaches, including the most sophisticated STGs. After conducting numerous experiments, we find that STHGN outperforms these methods with higher accuracy, resulting in a reduction of approximately 6-9% in mean absolute error (MAE) for crowd flow prediction.

Surface defects of railway trackside equipment pose a serious risk on the safety of railway transportation systems. Image-based surface defect detection methods have made significant progress. However, the image background of trackside equipment is complex, and there is a large amount of noise, which makes existing methods inadequate in accurately detecting small surface defect regions. To tackle with this issue, we propose a coarse-to-fine parallelizable surface defect detection approach to hierarchically detect the defects of trackside equipment. Firstly, a detection network is designed to locate and extract trackside equipment, which aims at roughly focusing the detection field from the original image to the region of interest of individual trackside equipment. Then, a novel semantic segmentation network is proposed to segment the major components of trackside equipment, so as to further finely focus on the defect regions. We apply multiple segmentation networks to parallelly segment various trackside equipment. In the segmentation network, a dense feature enhancement method is introduced to strengthen the high-level semantic information, and a feature partitioning enhancement strategy is designed to improve the segmentation performance for small defect regions. Finally, according to the visual characteristics of the segmentation output, we propose a defect recognizer to discriminate the defects. Extensive experimental results demonstrate that the proposed surface defect detection approach achieves higher accuracy for trackside equipment.

Deep neural networks (DNNs) have been widely employed to solve log anomaly detection and outperform a range of conventional methods. They have attained such striking success because they can usually explore and extract semantic information from a large volume of log data, which helps to infer complex log anomaly patterns more accurately. Despite its success in generalization accuracy, this data-driven approach can still suffer from a high vulnerability to adversarial attacks , which severely limits its practical use. To address this issue, several studies have proposed anomaly detectors to equip neural networks to improve their robustness. These anomaly detectors are built based on effective adversarial attack methods. Therefore, effective adversarial attack approaches are important for developing more efficient anomaly detectors, thereby improving neural network robustness. In this study, we propose two strong and effective black-box attackers, an attention-based and a gradient-based attacker, to defeat three target systems: MLP, AutoEncoder , and DeepLog. Our approach facilitates the generation of more effective adversarial examples with the help of the analysis of vulnerable logkeys. The proposed attention-based attacker leverages attention weights to achieve vulnerable logkeys and derive adversarial examples, which are implemented using our previously developed attention-based convolutional neural network model . The proposed gradient-based attacker calculates gradients based on potential vulnerable logkeys to seek an optimal adversarial sample. The experimental results showed that these two approaches significantly outperformed the state-of-the-art attacker model log anomaly mask (LAM). In particular, owing to its optimization, the proposed gradient-based attacker approach can significantly increase the misclassification rate on three target models, yields a 70% successful attack rate on DeepLog and greatly exceeds the baseline by 52%.

Abstract With versatility and complexity of computer systems, warning and errors are inevitable. To effectively monitor system’s status, system logs are critical. To detect anomalies in system logs, deep learning is a promising way to go. However, abnormal system logs in the real world are often difficult to collect, and effectively and accurately categorize the logs is an even time-consuming project. Thus, the data incompleteness is not conducive to the deep learning for this practical application. In this paper, we put forward a novel semi-supervised dual branch model that alleviate the need for large scale labeled logs for training a deep system log anomaly detector. Specifically, our model consists of two homogeneous networks that share the same parameters, one is called weak augmented teacher model and the other is termed as strong augmented student model. In the teacher model, the log features are augmented with small Gaussian noise, while in the student model, the strong augmentation is injected to force the model to learn a more robust feature representation with the guidance of teacher model provided soft labels. Furthermore, to further utilize unlabeled samples effectively, we propose a flexible label screening strategy that takes into account the confidence and stability of pseudo-labels. Experimental results show favorable effect of our model on prevalent HDFS and Hadoop Application datasets. Precisely, with only 30% training data labeled, our model can achieve the comparable results as the fully supervised version.

Semi-supervised learning (SSL) has been studied widely in standard benchmark datasets; however, real-world data often exhibit class-imbalanced distributions, which pose significant challenges for deep semi-supervised models. To address this issue, we design a three-stage learning framework, 3LPR, by combining unsupervised feature extraction, graph-based Label Propagation, and mixed data augmentation (MDA)-based label Reassignment. Specifically, we first explore the performance of supervised and unsupervised learning for feature extraction of class-imbalanced data and then establish our first stage of feature extraction through unsupervised learning. Then, we adopt graph network-based offline label propagation and sieving to effectively expand the labeled set to overcome the excessive label bias in the classifier during the training process. Finally, we propose a label reassignment (LRA) algorithm for class-imbalanced semi-supervised learning (CISSL) to train the expanded dataset, where the MDA strategy is adopted but with the label reassigned. The experimental results demonstrate that the proposed 3LPR framework for CISSL outperforms other state-of-the-art methods on various datasets.

With the development of deep learning and the emergence of massive video data, object tracking has great application prospects in many fields. However, most tracking algorithms can hardly get top performance with real-time speed. In this paper, we improved tracking model based on adversarial learning and to accelerate feature extraction we proposed an efficient and accurate method. We also present a Precise ROI Pooling (PrROIPooling) based algorithm for extracting more accurate representations of targets. Furthermore, a novel regularization term is defined to ensure the similarity between the generated features and the real features. Finally, the improved objective function with modulating factors is designed to handle the problem of imbalance in the number of positive and negative samples. Extensive experiments on three datasets have demonstrated our effectiveness and achieved competitive results compared with state-of-the-art methods.

Application delays caused by abnormal tasks arecommon problems in big data computing frameworks. Anabnormal task in Spark, which may run slowly withouterror or warning logs, not only reduces its resident node'sperformance, but also affects other nodes' efficiency.Spark log files report neither root causes of abnormal tasks,nor where and when abnormal scenarios happen. AlthoughSpark provides a “speculation” mechanism to detect stragglertasks, it can only detect tailed stragglers in each stage. Sincethe root causes of abnormal happening are complicated, thereare no effective ways to detect root causes.This paper proposes an approach to detect abnormality andanalyzes root causes using Spark log files. Unlike commononline monitoring or analysis tools, our approach is a pureoff-line method that can analyze abnormality accurately. Ourapproach consists of four steps. First, a parser preprocessesraw log files to generate structured log data. Second, ineach stage of Spark application, we choose features relatedto execution time and data locality of each task, as well asmemory usage and garbage collection of each node. Third,based on the selected features, we detect where and whenabnormalities happen. Finally, we analyze the problems usingweighted factors to decide the probability of root causes. In thispaper, we consider four potential root causes of abnormalities,which include CPU, memory, network, and disk. The proposedmethod has been tested on real-world Spark benchmarks.To simulate various scenario of root causes, we conductedinterference injections related to CPU, memory, network,and Disk. Our experimental results show that the proposedapproach is accurate on detecting abnormal tasks as well asfinding the root causes