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Keywords = unsupervised domain adaption

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21 pages, 4635 KB  
Article
Explainable Few-Shot Anomaly Detection for Real-Time Automotive Quality Control
by Safeh Clinton Mawah, Dagmawit Tadesse Aga, Shahrokh Hatefi, Farouk Smith and Yimesker Yihun
Processes 2025, 13(10), 3238; https://doi.org/10.3390/pr13103238 (registering DOI) - 11 Oct 2025
Viewed by 29
Abstract
Automotive manufacturing quality control faces persistent challenges such as limited defect samples, cross-domain variability, and the demand for interpretable decision-making. This work presents an explainable few-shot anomaly detection framework that integrates EfficientNet-based feature extraction, adaptive prototype learning, and component-specific attention mechanisms to address [...] Read more.
Automotive manufacturing quality control faces persistent challenges such as limited defect samples, cross-domain variability, and the demand for interpretable decision-making. This work presents an explainable few-shot anomaly detection framework that integrates EfficientNet-based feature extraction, adaptive prototype learning, and component-specific attention mechanisms to address these requirements. The system is designed for rapid adaptation to novel defect types while maintaining interpretability through a multi-modal explainable AI module that combines visual, quantitative, and textual outputs. Evaluation on automotive datasets demonstrates promising performance on evaluated automotive components, achieving 99.4% accuracy for engine wiring inspection and 98.8% for gear inspection, with improvements of 5.2–7.6% over state-of-the-art baselines, including traditional unsupervised methods (PaDiM, PatchCore), advanced approaches (FastFlow, CFA, DRAEM), and few-shot supervised methods (ProtoNet, MatchingNet, RelationNet, FEAT), and with only 0.63% cross-domain degradation between wiring and gear inspection tasks. The architecture operates under real-time industrial constraints, with an average inference time of 18.2 ms, throughput of 60 components per minute, and memory usage below 2 GB on RTX 3080 hardware. Ablation studies confirm the importance of prototype learning (−4.52%), component analyzers (−2.79%), and attention mechanisms (−2.21%), with K = 5 few-shot configuration providing the best trade-off between accuracy and adaptability. Beyond performance, the framework produces interpretable defect localization, root-cause analysis, and severity-based recommendations designed for manufacturing integration with execution systems via standardized industrial protocols. These results demonstrate a practical and scalable approach for intelligent quality control, enabling robust, interpretable, and adaptive inspection within the evaluated automotive components. Full article
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17 pages, 2289 KB  
Article
Aging-Aware Character Recognition with E-Textile Inputs
by Juncong Lin, Yujun Rong, Yao Cheng and Chenkang He
Electronics 2025, 14(19), 3964; https://doi.org/10.3390/electronics14193964 - 9 Oct 2025
Viewed by 193
Abstract
E-textiles, a type of textile integrated with conductive sensors, allows users to freely utilize any area of the body in a convenient and comfortable manner. Thus, interactions with e-textiles are attracting more and more attention, especially for text input. However, the functional aging [...] Read more.
E-textiles, a type of textile integrated with conductive sensors, allows users to freely utilize any area of the body in a convenient and comfortable manner. Thus, interactions with e-textiles are attracting more and more attention, especially for text input. However, the functional aging of e-textiles affects the characteristics and even the quality of the captured signal, presenting serious challenges for character recognition. This paper focuses on studying the behavior of e-textile functional aging and alleviating its impact on text input with an unsupervised domain adaptation technique, named A2TEXT (aging-aware e-textile-based text input). We first designed a deep kernel-based two-sample test method to validate the impact of functional aging on handwriting with an e-textile input. Based on that, we introduced a so-called Gabor domain adaptation technique, which adopts a novel Gabor orientation filter in feature extraction under an adversarial domain adaptation framework. We demonstrated superior performance compared to traditional models in four different transfer tasks, validating the effectiveness of our work. Full article
(This article belongs to the Special Issue End User Applications for Virtual, Augmented, and Mixed Reality)
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19 pages, 7932 KB  
Article
Unsupervised Domain Adaptation with Raman Spectroscopy for Rapid Autoimmune Disease Diagnosis
by Ziyang Zhang, Yang Liu, Cheng Chen, Xiaoyi Lv and Chen Chen
Sensors 2025, 25(19), 6186; https://doi.org/10.3390/s25196186 - 6 Oct 2025
Viewed by 297
Abstract
Autoimmune diseases constitute a broadly prevalent category of disorders. Conventional computer-aided diagnostic (CAD) techniques rely on large volumes of data paired with reliable annotations. However, the diverse symptomatology and diagnostic complexity of autoimmune diseases result in a scarcity of reliably labeled biological samples. [...] Read more.
Autoimmune diseases constitute a broadly prevalent category of disorders. Conventional computer-aided diagnostic (CAD) techniques rely on large volumes of data paired with reliable annotations. However, the diverse symptomatology and diagnostic complexity of autoimmune diseases result in a scarcity of reliably labeled biological samples. In this study, we propose a pseudo-label-based conditional domain adversarial network (CDAN-PL) framework by integrating Raman spectroscopy with domain adaptation technology, enabling label-free unsupervised transfer diagnosis of diseases. Compared to traditional unsupervised domain adaptation techniques, our CDAN-PL framework generates reliable pseudo-labels to ensure the robust implementation of conditional adversarial methods. Additionally, its spectral data-adaptive feature extraction techniques further solidify the model’s superiority in Raman spectroscopy-based disease diagnosis. CDAN-PL exhibits excellent performance in homologous transfer tasks, achieving an average accuracy of 92.3%—surpassing the baseline models’ 80.81% and 86.4%. Moreover, it attains an average accuracy of 90.05% in non-homologous transfer tasks, further validating its generalization capability. Full article
(This article belongs to the Collection Deep Learning in Biomedical Informatics and Healthcare)
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35 pages, 5316 KB  
Review
Machine Learning for Quality Control in the Food Industry: A Review
by Konstantinos G. Liakos, Vassilis Athanasiadis, Eleni Bozinou and Stavros I. Lalas
Foods 2025, 14(19), 3424; https://doi.org/10.3390/foods14193424 - 4 Oct 2025
Viewed by 994
Abstract
The increasing complexity of modern food production demands advanced solutions for quality control (QC), safety monitoring, and process optimization. This review systematically explores recent advancements in machine learning (ML) for QC across six domains: Food Quality Applications; Defect Detection and Visual Inspection Systems; [...] Read more.
The increasing complexity of modern food production demands advanced solutions for quality control (QC), safety monitoring, and process optimization. This review systematically explores recent advancements in machine learning (ML) for QC across six domains: Food Quality Applications; Defect Detection and Visual Inspection Systems; Ingredient Optimization and Nutritional Assessment; Packaging—Sensors and Predictive QC; Supply Chain—Traceability and Transparency and Food Industry Efficiency; and Industry 4.0 Models. Following a PRISMA-based methodology, a structured search of the Scopus database using thematic Boolean keywords identified 124 peer-reviewed publications (2005–2025), from which 25 studies were selected based on predefined inclusion and exclusion criteria, methodological rigor, and innovation. Neural networks dominated the reviewed approaches, with ensemble learning as a secondary method, and supervised learning prevailing across tasks. Emerging trends include hyperspectral imaging, sensor fusion, explainable AI, and blockchain-enabled traceability. Limitations in current research include domain coverage biases, data scarcity, and underexplored unsupervised and hybrid methods. Real-world implementation challenges involve integration with legacy systems, regulatory compliance, scalability, and cost–benefit trade-offs. The novelty of this review lies in combining a transparent PRISMA approach, a six-domain thematic framework, and Industry 4.0/5.0 integration, providing cross-domain insights and a roadmap for robust, transparent, and adaptive QC systems in the food industry. Full article
(This article belongs to the Special Issue Artificial Intelligence for the Food Industry)
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29 pages, 3280 KB  
Article
MAJATNet: A Lightweight Multi-Scale Attention Joint Adaptive Adversarial Transfer Network for Bearing Unsupervised Cross-Domain Fault Diagnosis
by Lin Song, Yanlin Zhao, Junjie He, Simin Wang, Boyang Zhong and Fei Wang
Entropy 2025, 27(10), 1011; https://doi.org/10.3390/e27101011 - 26 Sep 2025
Viewed by 236
Abstract
Rolling bearings are essential for modern mechanical equipment and serve in various operational environments. This paper addresses the challenge of vibration data discrepancies in bearings across different operating conditions, which often results in inaccurate fault diagnosis. To tackle this related limitation, a novel [...] Read more.
Rolling bearings are essential for modern mechanical equipment and serve in various operational environments. This paper addresses the challenge of vibration data discrepancies in bearings across different operating conditions, which often results in inaccurate fault diagnosis. To tackle this related limitation, a novel lightweight multi-scale attention-based joint adaptive adversarial transfer network, termed MAJATNet, is developed. The proposed network integrates a feature extraction network innovation module with an improved loss function, namely IJA loss. The feature extraction module employs a one-dimensional multi-scale attention residual structure to derive characteristics from monitoring data of source and target domains. IJA loss evaluates the joint distribution discrepancy of high-dimensional features and labels between these domains. IJA loss integrates a joint maximum mean discrepancy (JMMD) loss with a domain adversarial learning loss, which directs the model’s focus toward categorical features while minimizing domain-specific features. The performance and advantages of MAJATNet are demonstrated through cross-domain fault diagnosis experiments using bearing datasets. Experimental results show that the proposed method can significantly improve the accuracy of cross-domain fault diagnosis for bearings. Full article
(This article belongs to the Special Issue Failure Diagnosis of Complex Systems)
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37 pages, 1134 KB  
Article
SOMTreeNet: A Hybrid Topological Neural Model Combining Self-Organizing Maps and BIRCH for Structured Learning
by Yunus Doğan
Mathematics 2025, 13(18), 2958; https://doi.org/10.3390/math13182958 - 12 Sep 2025
Viewed by 505
Abstract
This study introduces SOMTreeNet, a novel hybrid neural model that integrates Self-Organizing Maps (SOMs) with BIRCH-inspired clustering features to address structured learning in a scalable and interpretable manner. Unlike conventional deep learning models, SOMTreeNet is designed with a recursive and modular topology that [...] Read more.
This study introduces SOMTreeNet, a novel hybrid neural model that integrates Self-Organizing Maps (SOMs) with BIRCH-inspired clustering features to address structured learning in a scalable and interpretable manner. Unlike conventional deep learning models, SOMTreeNet is designed with a recursive and modular topology that supports both supervised and unsupervised learning, enabling tasks such as classification, regression, clustering, anomaly detection, and time-series analysis. Extensive experiments were conducted using various publicly available datasets across five analytical domains: classification, regression, clustering, time-series forecasting, and image classification. These datasets cover heterogeneous structures including tabular, temporal, and visual data, allowing for a robust evaluation of the model’s generalizability. Experimental results demonstrate that SOMTreeNet consistently achieves competitive or superior performance compared to traditional machine learning and deep learning methods while maintaining a high degree of interpretability and adaptability. Its biologically inspired hierarchical structure facilitates transparent decision-making and dynamic model growth, making it particularly suitable for real-world applications that demand both accuracy and explainability. Overall, SOMTreeNet offers a versatile framework for learning from complex data while preserving the transparency and modularity often lacking in black-box models. Full article
(This article belongs to the Special Issue New Advances in Data Analytics and Mining)
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22 pages, 1682 KB  
Article
Unsupervised Domain Adaptation for Automatic Polyp Segmentation Using Synthetic Data
by Ioanna Malli, Ioannis A. Vezakis, Ioannis Kakkos, Theodosis Kalamatianos and George K. Matsopoulos
Appl. Sci. 2025, 15(17), 9829; https://doi.org/10.3390/app15179829 - 8 Sep 2025
Viewed by 598
Abstract
Colorectal cancer is a significant health concern that can often be prevented through early detection of precancerous polyps during routine screenings. Although artificial intelligence (AI) methods have shown potential in reducing polyp miss rates, clinical adoption remains limited due to concerns over patient [...] Read more.
Colorectal cancer is a significant health concern that can often be prevented through early detection of precancerous polyps during routine screenings. Although artificial intelligence (AI) methods have shown potential in reducing polyp miss rates, clinical adoption remains limited due to concerns over patient privacy, limited access to annotated data, and the high cost of expert labeling. To address these challenges, we propose an unsupervised domain adaptation (UDA) approach that leverages a fully synthetic colonoscopy dataset, SynthColon, and adapts it to real-world, unlabeled data. Our method builds on the DAFormer framework and integrates a Transformer-based hierarchical encoder, a context-aware feature fusion decoder, and a self-training strategy. We evaluate our approach on the Kvasir-SEG and CVC-ClinicDB datasets. Results show that our method achieves improved segmentation performance of 69% mIoU compared to the baseline approach from the original SynthColon study and remains competitive with models trained on enhanced versions of the dataset. Full article
(This article belongs to the Special Issue AI-Based Biomedical Signal and Image Processing)
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17 pages, 17890 KB  
Article
AnomNet: A Dual-Stage Centroid Optimization Framework for Unsupervised Anomaly Detection
by Yuan Gao, Yu Wang, Xiaoguang Tu and Jiaqing Shen
J. Imaging 2025, 11(9), 301; https://doi.org/10.3390/jimaging11090301 - 3 Sep 2025
Viewed by 517
Abstract
Anomaly detection plays a vital role in ensuring product quality and operational safety across various industrial applications, from manufacturing to infrastructure monitoring. However, current methods often struggle with challenges such as limited generalization to complex multimodal anomalies, poor adaptation to domain-specific patterns, and [...] Read more.
Anomaly detection plays a vital role in ensuring product quality and operational safety across various industrial applications, from manufacturing to infrastructure monitoring. However, current methods often struggle with challenges such as limited generalization to complex multimodal anomalies, poor adaptation to domain-specific patterns, and reduced feature discriminability due to domain gaps between pre-trained models and industrial data. To address these issues, we propose AnomNet, a novel deep anomaly detection framework that integrates a lightweight feature adapter module to bridge domain discrepancies and enhance multi-scale feature discriminability from pre-trained backbones. AnomNet is trained using a dual-stage centroid learning strategy: the first stage employs separation and entropy regularization losses to stabilize and optimize the centroid representation of normal samples; the second stage introduces a centroid-based contrastive learning mechanism to refine decision boundaries by adaptively managing inter- and intra-class feature relationships. The experimental results on the MVTec AD dataset demonstrate the superior performance of AnomNet, achieving a 99.5% image-level AUROC and 98.3% pixel-level AUROC, underscoring its effectiveness and robustness for anomaly detection and localization in industrial environments. Full article
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22 pages, 1390 KB  
Article
Masked and Clustered Pre-Training for Geosynchronous Satellite Maneuver Detection
by Shu-He Tian, Yu-Qiang Fang, Hua-Fei Diao, Di Luo and Ya-Sheng Zhang
Remote Sens. 2025, 17(17), 2994; https://doi.org/10.3390/rs17172994 - 28 Aug 2025
Viewed by 624
Abstract
Geosynchronous satellite maneuver detection is critical for enhancing space situational awareness and inferring satellite intent. However, traditional methods often require high-quality orbital sequence data and heavily rely on hand-crafted features, limiting their effectiveness in complex real-world environments. While recent neural network-based approaches have [...] Read more.
Geosynchronous satellite maneuver detection is critical for enhancing space situational awareness and inferring satellite intent. However, traditional methods often require high-quality orbital sequence data and heavily rely on hand-crafted features, limiting their effectiveness in complex real-world environments. While recent neural network-based approaches have shown promise, they are typically trained in scene or task-specific settings, resulting in limited generalization and adaptability. To address these challenges, we propose MC-MD, a pre-training framework that integrates Masked and Clustered learning strategies to improve the robustness and transferability of geosynchronous satellite Maneuver Detection. Specifically, we introduce a masked prediction module that applies both time- and frequency-domain masking to help the model capture temporal dynamics more effectively. Meanwhile, a cluster-based module guides the model to learn discriminative representations of different maneuver patterns through unsupervised clustering, mitigating the negative impact of distribution shifts across scenarios. By combining these two strategies, MC-MD captures diverse maneuver behaviors and enhances cross-scenario detection performance. Extensive experiments on both simulated and real-world datasets demonstrate that MCMD achieves significant performance gains over the strongest baseline, with improvements of 8.54% in Precision and 7.8% in F1-Score. Furthermore, reconstructed trajectories analysis shows that MC-MD more accurately aligns with the ground-truth maneuver sequence, highlighting its effectiveness in satellite maneuver detection tasks. Full article
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20 pages, 9232 KB  
Article
Anomaly-Detection Framework for Thrust Bearings in OWC WECs Using a Feature-Based Autoencoder
by Se-Yun Hwang, Jae-chul Lee, Soon-sub Lee and Cheonhong Min
J. Mar. Sci. Eng. 2025, 13(9), 1638; https://doi.org/10.3390/jmse13091638 - 27 Aug 2025
Viewed by 493
Abstract
An unsupervised anomaly-detection framework is proposed and field validated for thrust-bearing monitoring in the impulse turbine of a shoreline oscillating water-column (OWC) wave energy converter (WEC) off Jeju Island, Korea. Operational monitoring is constrained by nonstationary sea states, scarce fault labels, and low-rate [...] Read more.
An unsupervised anomaly-detection framework is proposed and field validated for thrust-bearing monitoring in the impulse turbine of a shoreline oscillating water-column (OWC) wave energy converter (WEC) off Jeju Island, Korea. Operational monitoring is constrained by nonstationary sea states, scarce fault labels, and low-rate supervisory logging at 20 Hz. To address these conditions, a 24 h period of normal operation was median-filtered to suppress outliers, and six physically motivated time-domain features were computed from triaxial vibration at 10 s intervals: absolute mean; standard deviation (STD); root mean square (RMS); skewness; shape factor (SF); and crest factor (CF, peak divided by RMS). A feature-based autoencoder was trained to reconstruct the feature vectors, and reconstruction error was evaluated with an adaptive threshold derived from the moving mean and moving standard deviation to accommodate baseline drift. Performance was assessed on a 2 h test segment that includes a 40 min simulated fault window created by doubling the triaxial vibration amplitudes prior to preprocessing and feature extraction. The detector achieved accuracy of 0.99, precision of 1.00, recall of 0.98, and F1 score of 0.99, with no false positives and five false negatives. These results indicate dependable detection at low sampling rates with modest computational cost. The chosen feature set provides physical interpretability under the 20 Hz constraint, and denoising stabilizes indicators against marine transients, supporting applicability in operational settings. Limitations associated with simulated faults are acknowledged. Future work will incorporate long-term field observations with verified fault progressions, cross-site validation, and integration with digital-twin-enabled maintenance. Full article
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30 pages, 578 KB  
Article
Two-Stage Mining of Linkage Risk for Data Release
by Runshan Hu, Yuanguo Lin, Mu Yang, Yuanhui Yu and Vladimiro Sassone
Mathematics 2025, 13(17), 2731; https://doi.org/10.3390/math13172731 - 25 Aug 2025
Viewed by 572
Abstract
Privacy risk mining, a crucial domain in data privacy protection, endeavors to uncover potential information among datasets that could be linked to individuals’ sensitive data. Existing anonymization and privacy assessment techniques either lack quantitative granularity or fail to adapt to dynamic, heterogeneous data [...] Read more.
Privacy risk mining, a crucial domain in data privacy protection, endeavors to uncover potential information among datasets that could be linked to individuals’ sensitive data. Existing anonymization and privacy assessment techniques either lack quantitative granularity or fail to adapt to dynamic, heterogeneous data environments. In this work, we propose a unified two-phase linkability quantification framework that systematically measures privacy risks at both the inter-dataset and intra-dataset levels. Our approach integrates unsupervised clustering on attribute distributions with record-level matching to compute interpretable, fine-grained risk scores. By aligning risk measurement with regulatory standards such as the GDPR, our framework provides a practical, scalable solution for safeguarding user privacy in evolving data-sharing ecosystems. Extensive experiments on real-world and synthetic datasets show that our method achieves up to 96.7% precision in identifying true linkage risks, outperforming the compared baseline by 13 percentage points under identical experimental settings. Ablation studies further demonstrate that the hierarchical risk fusion strategy improves sensitivity to latent vulnerabilities, providing more actionable insights than previous privacy gain-based metrics. Full article
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24 pages, 2709 KB  
Article
Unsupervised Person Re-Identification via Deep Attribute Learning
by Shun Zhang, Yaohui Xu, Xuebin Zhang, Boyang Cheng and Ke Wang
Future Internet 2025, 17(8), 371; https://doi.org/10.3390/fi17080371 - 15 Aug 2025
Viewed by 622
Abstract
Driven by growing public security demands and the advancement of intelligent surveillance systems, person re-identification (ReID) has emerged as a prominent research focus in the field of computer vision. However, this task presents challenges due to its high sensitivity to variations in visual [...] Read more.
Driven by growing public security demands and the advancement of intelligent surveillance systems, person re-identification (ReID) has emerged as a prominent research focus in the field of computer vision. However, this task presents challenges due to its high sensitivity to variations in visual appearance caused by factors such as body pose and camera parameters. Although deep learning-based methods have achieved marked progress in ReID, the high cost of annotation remains a challenge that cannot be overlooked. To address this, we propose an unsupervised attribute learning framework that eliminates the need for costly manual annotations while maintaining high accuracy. The framework learns the mid-level human attributes (such as clothing type and gender) that are robust to substantial visual appearance variations and can hence boost the accuracy of attributes with a small amount of labeled data. To carry out our framework, we present a part-based convolutional neural network (CNN) architecture, which consists of two components for image and body attribute learning on a global level and upper- and lower-body image and attribute learning at a local level. The proposed architecture is trained to learn attribute-semantic and identity-discriminative feature representations simultaneously. For model learning, we first train our part-based network using a supervised approach on a labeled attribute dataset. Then, we apply an unsupervised clustering method to assign pseudo-labels to unlabeled images in a target dataset using our trained network. To improve feature compatibility, we introduce an attribute consistency scheme for unsupervised domain adaptation on this unlabeled target data. During training on the target dataset, we alternately perform three steps: extracting features with the updated model, assigning pseudo-labels to unlabeled images, and fine-tuning the model. Through a unified framework that fuses complementary attribute-label and identity label information, our approach achieves considerable improvements of 10.6% and 3.91% mAP on Market-1501→DukeMTMC-ReID and DukeMTMC-ReID→Market-1501 unsupervised domain adaptation tasks, respectively. Full article
(This article belongs to the Special Issue Advances in Deep Learning and Next-Generation Internet Technologies)
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21 pages, 8269 KB  
Article
Context-Aware Feature Adaptation for Mitigating Negative Transfer in 3D LiDAR Semantic Segmentation
by Lamiae El Mendili, Sylvie Daniel and Thierry Badard
Remote Sens. 2025, 17(16), 2825; https://doi.org/10.3390/rs17162825 - 14 Aug 2025
Viewed by 540
Abstract
Semantic segmentation of 3D LiDAR point clouds is crucial for autonomous driving and urban modeling but requires extensive labeled data. Unsupervised domain adaptation from synthetic to real data offers a promising solution, yet faces the challenge of negative transfer, particularly due to context [...] Read more.
Semantic segmentation of 3D LiDAR point clouds is crucial for autonomous driving and urban modeling but requires extensive labeled data. Unsupervised domain adaptation from synthetic to real data offers a promising solution, yet faces the challenge of negative transfer, particularly due to context shifts between domains. This paper introduces Context-Aware Feature Adaptation, a novel approach to mitigate negative transfer in 3D unsupervised domain adaptation. The proposed approach disentangles object-specific and context-specific features, refines source context features through cross-attention with target information, and adaptively fuses the results. We evaluate our approach on challenging synthetic-to-real adaptation scenarios, demonstrating consistent improvements over state-of-the-art domain adaptation methods with up to 7.9% improvement in classes subject to context shift. Our comprehensive domain shift analysis reveals a positive correlation between context shift magnitude and performance improvement. Extensive ablation studies and visualizations further validate the efficacy in handling context shift for 3D semantic segmentation. Full article
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24 pages, 5723 KB  
Article
Fault Diagnosis of Rolling Bearings Under Variable Speed for Energy Conversion Systems: An ACMD and SP-DPS Clustering Approach with Traction Motor Validation
by Shunyan Peng, Enyong Xu, Yuan Zhuang, Hanqing Jian, Zhenzhen Jin and Zexian Wei
Energies 2025, 18(16), 4254; https://doi.org/10.3390/en18164254 - 11 Aug 2025
Viewed by 508
Abstract
Rolling bearing failures in rotating machinery essential to energy systems (e.g., motors, generators, or turbines) can cause downtime, energy inefficiency, and safety hazards—especially under variable speed conditions common in traction drives. Traditional diagnosis methods struggle with nonstationary signals from speed variations. In response, [...] Read more.
Rolling bearing failures in rotating machinery essential to energy systems (e.g., motors, generators, or turbines) can cause downtime, energy inefficiency, and safety hazards—especially under variable speed conditions common in traction drives. Traditional diagnosis methods struggle with nonstationary signals from speed variations. In response, there is a growing trend toward unsupervised and adaptive signal processing techniques, which offer better generalization in complex operating scenarios. This paper proposes an intelligent fault diagnosis framework combining Adaptive Chirp Mode Decomposition (ACMD)-based order tracking with a novel Shortest Paths Density Peak Search (SP-DPS) clustering algorithm. ACMD is chosen for its proven ability to extract instantaneous speed profiles from nonstationary signals, enabling angular domain resampling and quasi-stationary signal representation. SP-DPS enhances clustering robustness by incorporating global structure awareness into the analysis of statistical features in both the time and frequency domains. The method is validated using both a public bearing dataset and a custom-built metro traction motor test bench, representative of electric traction systems. The results show over 96% diagnostic accuracy under significant speed fluctuations, outperforming several state-of-the-art clustering approaches. This study presents a scalable and accurate unsupervised solution for bearing fault diagnosis, with strong potential to improve reliability, reduce maintenance costs, and prevent energy losses in critical energy conversion machinery. Full article
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22 pages, 5044 KB  
Article
Towards Robust Hyperspectral Target Detection via Test-Time Spectrum Adaptation
by Robin Gerster and Peter Stütz
Remote Sens. 2025, 17(16), 2756; https://doi.org/10.3390/rs17162756 - 8 Aug 2025
Viewed by 665
Abstract
Target detection is a cornerstone task in hyperspectral image processing but faces significant challenges due to domain gaps. While statistical detectors like Constrained Energy Minimization (CEM) and Adaptive Cosine Estimator (ACE) are not prone to learned biases, in practice they still suffer from [...] Read more.
Target detection is a cornerstone task in hyperspectral image processing but faces significant challenges due to domain gaps. While statistical detectors like Constrained Energy Minimization (CEM) and Adaptive Cosine Estimator (ACE) are not prone to learned biases, in practice they still suffer from mismatches between the reference target spectrum and the spectral characteristics of the target in the test scene. We propose Test-time Adaptive Spectrum Refinement (TASR), a novel framework addressing this problem. TASR operates in an interpretable, lightweight, data-efficient manner, requiring only a single labeled source image of the target material. At test time, TASR dynamically refines the target spectrum to better align with the spectral properties of the test scene. This adaptive refinement enables detectors to effectively handle data with spectral variations, bridging the gap between the source and test spectra. To validate TASR, we conduct extensive experiments on established benchmarks and introduce a new dataset—ShadySunnyDiffuse (SSD)—which explicitly tests detector robustness to naturally occurring illumination changes. We further demonstrate the method’s versatility by applying it to camouflage detection and show compatibility with multiple statistical detectors. Our results establish TASR as a state-of-the-art approach in domain-adaptive hyperspectral target detection and target spectrum management. Full article
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