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Multivariate time-series anomaly detection is essential for reliable industrial control, telemetry, and service monitoring. However, the evolving inter-variable dependencies and inevitable noise render it challenging. Existing methods often…

Machine Learning · Computer Science 2026-02-25 Zhongpeng Qi , Jun Zhang , Wei Li , Zhuoxuan Liang

Anomaly detection from graph data has drawn much attention due to its practical significance in many critical applications including cybersecurity, finance, and social networks. Existing data mining and machine learning methods are either…

Machine Learning · Computer Science 2022-01-25 Yu Zheng , Ming Jin , Yixin Liu , Lianhua Chi , Khoa T. Phan , Yi-Ping Phoebe Chen

Distance-based anomaly detection methods rely on compact in-distribution (ID) embeddings that are well separated from anomalies. However, conventional contrastive learning strategies often struggle to achieve this balance, either promoting…

Machine Learning · Computer Science 2026-02-02 Willian T. Lunardi , Abdulrahman Banabila , Dania Herzalla , Martin Andreoni

Disentangling complex causal relationships is important for accurate detection of anomalies. In multivariate time series analysis, dynamic interactions among data variables over time complicate the interpretation of causal relationships.…

Machine Learning · Computer Science 2025-10-14 Wonah Kim , Jeonghyeon Park , Dongsan Jun , Jungkyu Han , Sejin Chun

Contrastive Analysis (CA) detects anomalies by contrasting patterns unique to a target group (e.g., unhealthy subjects) from those in a background group (e.g., healthy subjects). In the context of brain MRIs, existing CA approaches rely on…

Computer Vision and Pattern Recognition · Computer Science 2025-07-02 Cristiano Patrício , Carlo Alberto Barbano , Attilio Fiandrotti , Riccardo Renzulli , Marco Grangetto , Luis F. Teixeira , João C. Neves

End-to-end Automatic Speech Recognition (ASR) models are usually trained to optimize the loss of the whole token sequence, while neglecting explicit phonemic-granularity supervision. This could result in recognition errors due to…

Audio and Speech Processing · Electrical Eng. & Systems 2022-06-22 Li Fu , Xiaoxiao Li , Runyu Wang , Lu Fan , Zhengchen Zhang , Meng Chen , Youzheng Wu , Xiaodong He

A topic of great current interest is Causal Representation Learning (CRL), whose goal is to learn a causal model for hidden features in a data-driven manner. Unfortunately, CRL is severely ill-posed since it is a combination of the two…

Machine Learning · Statistics 2024-06-10 Hiroshi Morioka , Aapo Hyvärinen

Contrastive learning (CL) has emerged as a promising approach for representation learning in time series data by embedding similar pairs closely while distancing dissimilar ones. However, existing CL methods often introduce false negative…

Machine Learning · Computer Science 2024-10-15 Yu Wu , Ting Dang , Dimitris Spathis , Hong Jia , Cecilia Mascolo

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

As an exemplary self-supervised approach for representation learning, time-series contrastive learning has exhibited remarkable advancements in contemporary research. While recent contrastive learning strategies have focused on how to…

Machine Learning · Computer Science 2024-08-27 Xiyuan Jin , Jing Wang , Lei Liu , Youfang Lin

With the recent advances in technology, a wide range of systems continue to collect a large amount of data over time and thus generate time series. Time-Series Anomaly Detection (TSAD) is an important task in various time-series…

Machine Learning · Computer Science 2025-05-01 Thi Kieu Khanh Ho , Ali Karami , Narges Armanfard

Contrastive learning methods for time series anomaly detection (TSAD) heavily depend on the quality of negative sample construction. However, existing strategies based on random perturbations or pseudo-anomaly injection often struggle to…

Machine Learning · Computer Science 2026-03-20 Xiancheng Wang , Lin Wang , Zhibo Zhang , Rui Wang , Minghang Zhao

This paper investigates unsupervised anomaly detection in multivariate time-series data using reinforcement learning (RL) in the latent space of an autoencoder. A significant challenge is the limited availability of anomalous data, often…

Machine Learning · Computer Science 2025-02-11 Saba Sanami , Amir G. Aghdam

Unsupervised anomaly detection in time series has been a pivotal research area for decades. Current mainstream approaches focus on learning normality, on the assumption that all or most of the samples in the training set are normal.…

Machine Learning · Computer Science 2025-05-28 Kohei Obata , Yasuko Matsubara , Yasushi Sakurai

Given the scarcity of anomalies in real-world applications, the majority of literature has been focusing on modeling normality. The learned representations enable anomaly detection as the normality model is trained to capture certain key…

Machine Learning · Computer Science 2022-07-05 Feng Xue , Weizhong Yan

Graph-based anomaly detection has been widely used for detecting malicious activities in real-world applications. Existing attempts to address this problem have thus far focused on structural feature engineering or learning in the binary…

Machine Learning · Computer Science 2022-08-31 Bo Chen , Jing Zhang , Xiaokang Zhang , Yuxiao Dong , Jian Song , Peng Zhang , Kaibo Xu , Evgeny Kharlamov , Jie Tang

Contrastive learning is a family of self-supervised methods where a model is trained to solve a classification task constructed from unlabeled data. It has recently emerged as one of the leading learning paradigms in the absence of labels…

Machine Learning · Statistics 2021-03-05 Bingbin Liu , Pradeep Ravikumar , Andrej Risteski

Contrastive learning has achieved remarkable success in representation learning via self-supervision in unsupervised settings. However, effectively adapting contrastive learning to supervised learning tasks remains as a challenge in…

Computation and Language · Computer Science 2022-01-24 Qianben Chen , Richong Zhang , Yaowei Zheng , Yongyi Mao

This paper addresses the challenges of complex dependencies and diverse anomaly patterns in cloud service environments by proposing a dependency modeling and anomaly detection method that integrates contrastive learning. The method…

Machine Learning · Computer Science 2025-10-16 Yue Xing , Yingnan Deng , Heyao Liu , Ming Wang , Yun Zi , Xiaoxuan Sun

Anomaly detection (AD) plays a vital role across a wide range of real-world domains by identifying data instances that deviate from expected patterns, potentially signaling critical events such as system failures, fraudulent activities, or…

Machine Learning · Computer Science 2025-07-11 Amirhossein Sadough , Mahyar Shahsavari , Mark Wijtvliet , Marcel van Gerven