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Effective anomaly detection in time series is pivotal for modern industrial applications and financial systems. Due to the scarcity of anomaly labels and the high cost of manual labeling, reconstruction-based unsupervised approaches have…

Machine Learning · Computer Science 2025-09-25 Tiejun Wang , Rui Wang , Xudong Mou , Mengyuan Ma , Tianyu Wo , Renyu Yang , Xudong Liu

Anomaly detection in multivariate time series (MTS) is hindered by dynamic inter-variable dependencies and feature entanglement under spectral noise, and in practice, is further complicated by the absence of anomaly labels. Existing…

Machine Learning · Computer Science 2026-05-25 Yunhua Pei , Zixing Song , Jin Zheng , John Cartlidge

The application of supervised models to clinical screening tasks is challenging due to the need for annotated data for each considered pathology. Unsupervised Anomaly Detection (UAD) is an alternative approach that aims to identify any…

Image and Video Processing · Electrical Eng. & Systems 2025-01-24 Finn Behrendt , Debayan Bhattacharya , Robin Mieling , Lennart Maack , Julia Krüger , Roland Opfer , Alexander Schlaefer

This paper introduces the first fully unsupervised domain adaptation (UDA) framework for unsupervised anomaly detection (UAD). The performance of UAD techniques degrades significantly in the presence of a domain shift, difficult to avoid in…

Machine Learning · Computer Science 2025-12-29 Nesryne Mejri , Enjie Ghorbel , Anis Kacem , Pavel Chernakov , Niki Foteinopoulou , Djamila Aouada

In this paper, we introduce a novel task termed unified anomaly detection and classification, which aims to simultaneously detect anomalous regions in images and identify their specific categories. Existing methods typically treat anomaly…

Computer Vision and Pattern Recognition · Computer Science 2026-02-04 Ximiao Zhang , Min Xu , Zheng Zhang , Junlin Hu , Xiuzhuang Zhou

Graph anomaly detection (GAD) is a critical task in graph machine learning, with the primary objective of identifying anomalous nodes that deviate significantly from the majority. This task is widely applied in various real-world scenarios,…

Machine Learning · Computer Science 2025-07-03 Xiang Li , Jianpeng Qi , Zhongying Zhao , Guanjie Zheng , Lei Cao , Junyu Dong , Yanwei Yu

Anomaly detection using a network-based approach is one of the most efficient ways to identify abnormal events such as fraud, security breaches, and system faults in a variety of applied domains. While most of the earlier works address the…

Artificial Intelligence · Computer Science 2025-01-22 Hossein Rafieizadeh , Hadi Zare , Mohsen Ghassemi Parsa , Hadi Davardoust , Meshkat Shariat Bagheri

Unsupervised anomaly detection (UAD) is a widely adopted approach in industry due to rare anomaly occurrences and data imbalance. A desirable characteristic of an UAD model is contained generalization ability which excels in the…

Computer Vision and Pattern Recognition · Computer Science 2023-08-29 YeongHyeon Park , Sungho Kang , Myung Jin Kim , Hyeonho Jeong , Hyunkyu Park , Hyeong Seok Kim , Juneho Yi

Unsupervised Anomaly Detection (UAD) with incremental training is crucial in industrial manufacturing, as unpredictable defects make obtaining sufficient labeled data infeasible. However, continual learning methods primarily rely on…

Computer Vision and Pattern Recognition · Computer Science 2024-01-03 Jiaqi Liu , Kai Wu , Qiang Nie , Ying Chen , Bin-Bin Gao , Yong Liu , Jinbao Wang , Chengjie Wang , Feng Zheng

We study the problem of semi-supervised anomaly detection with domain adaptation. Given a set of normal data from a source domain and a limited amount of normal examples from a target domain, the goal is to have a well-performing anomaly…

Machine Learning · Computer Science 2020-06-09 Ziyi Yang , Iman Soltani Bozchalooi , Eric Darve

Reliably detecting anomalies in a given set of images is a task of high practical relevance for visual quality inspection, surveillance, or medical image analysis. Autoencoder neural networks learn to reconstruct normal images, and hence…

Machine Learning · Computer Science 2019-01-21 Laura Beggel , Michael Pfeiffer , Bernd Bischl

Unsupervised anomaly detection (UAD) methods are trained with normal (or healthy) images only, but during testing, they are able to classify normal and abnormal (or disease) images. UAD is an important medical image analysis (MIA) method to…

Image and Video Processing · Electrical Eng. & Systems 2023-08-16 Yu Tian , Fengbei Liu , Guansong Pang , Yuanhong Chen , Yuyuan Liu , Johan W. Verjans , Rajvinder Singh , Gustavo Carneiro

Anomaly detection with only prior knowledge from normal samples attracts more attention because of the lack of anomaly samples. Existing CNN-based pixel reconstruction approaches suffer from two concerns. First, the reconstruction source…

Computer Vision and Pattern Recognition · Computer Science 2022-12-12 Zhiyuan You , Kai Yang , Wenhan Luo , Lei Cui , Yu Zheng , Xinyi Le

Unsupervised anomaly detection (UAD) seeks to localize the anomaly mask of an input image with respect to normal samples. Either by reconstructing normal counterparts (reconstruction-based) or by learning an image feature embedding space…

Image and Video Processing · Electrical Eng. & Systems 2025-10-06 Zhe Zhang , Mingxiu Cai , Hanxiao Wang , Gaochang Wu , Tianyou Chai , Xiatian Zhu

Previous feature alignment methods in Unsupervised domain adaptation(UDA) mostly only align global features without considering the mismatch between class-wise features. In this work, we propose a new coarse-to-fine feature alignment method…

Computer Vision and Pattern Recognition · Computer Science 2021-03-24 Shiyu Tang , Peijun Tang , Yanxiang Gong , Zheng Ma , Mei Xie

Anomaly detection and localization without any manual annotations and prior knowledge is a challenging task under the setting of unsupervised learning. The existing works achieve excellent performance in the anomaly detection, but with…

Computer Vision and Pattern Recognition · Computer Science 2024-05-16 Honghui Chen , Pingping Chen , Huan Mao , Mengxi Jiang

In image anomaly detection, Autoencoders are the popular methods that reconstruct the input image that might contain anomalies and output a clean image with no abnormalities. These Autoencoder-based methods usually calculate the anomaly…

Image and Video Processing · Electrical Eng. & Systems 2021-05-24 Masaki Nakanishi , Kazuki Sato , Hideo Terada

Current state-of-the-art multi-class unsupervised anomaly detection (MUAD) methods rely on training encoder-decoder models to reconstruct anomaly-free features. We first show these approaches have an inherent fidelity-stability dilemma in…

Computer Vision and Pattern Recognition · Computer Science 2026-02-03 Xingwu Zhang , Guanxuan Li , Paul Henderson , Gerardo Aragon-Camarasa , Zijun Long

Anomaly detection (AD) in images, identifying significant deviations from normality, is a critical issue in computer vision. This paper introduces a novel approach to dimensionality reduction for AD using pre-trained convolutional neural…

Computer Vision and Pattern Recognition · Computer Science 2023-12-05 Tetiana Gula , João P C Bertoldo

Anomaly detection has a wide range of applications and is especially important in industrial quality inspection. Currently, many top-performing anomaly-detection models rely on feature-embedding methods. However, these methods do not…

Computer Vision and Pattern Recognition · Computer Science 2023-07-07 Shiqi Deng , Zhiyu Sun , Ruiyan Zhuang , Jun Gong