{"title":"Anomaly Detection Using Data-Driven Sparse Sensors: Combination of Modal Representation and Sensor Optimization for Sensing of Targeted Variable","authors":"Yuji Saito;Ryoma Inoba;Yasuo Sasaki;Takayuki Nagata;Keigo Yamada;Taku Nonomura","doi":"10.1109/LSENS.2025.3591066","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3591066","url":null,"abstract":"We propose an anomaly detection method based on modal representation and a noise-robust sparse sensor position optimization method. We focus on the detection of anomalies in global sea surface temperature field observations indicative of El Niño and La Niña phenomena. For evaluation, we compared four methods, namely, the random linear least squares estimation method, the determinant-based greedy linear least squares method, the DG with noise covariance generalized linear least squares (DG/NC-GLS) estimation, and the Bayesian DG Bayesian estimation (BDG-BE) method of which the extension is proposed in this study. The results demonstrate that the DG/NC-GLS and BDG-BE methods outperform the other methods in anomaly detection. In fact, the DG/NC-GLS and BDG-BE methods achieve high accuracy and precision of over 81% with only 20 sensors (44 219 sensor candidates) for anomaly detection in global sea surface temperature field observations.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 8","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zexing Zhang;Huimin Lu;Qingxin Zhao;Kai Wen;Bing Liu
{"title":"PPG Sensor-Based Biometric Identification and Physiological Analysis via Temporal-Frequency Disentanglement With Liquid Neural Networks","authors":"Zexing Zhang;Huimin Lu;Qingxin Zhao;Kai Wen;Bing Liu","doi":"10.1109/LSENS.2025.3590543","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3590543","url":null,"abstract":"Photoplethysmography (PPG) sensors support both physiological monito- ring and biometric identification, making them key components in wearable sensing systems. However, real-world applications face challenges from signal nonstationarity and physiological variability. This work proposes a temporal-frequency manifold disentanglement framework to improve the robustness and accuracy of PPG-based biometric recognition. A closed-form continuous-time (CfC) liquid neural network captures temporal and spectral features from raw PPG signals, while an orthogonal manifold projection separates identity-related and physiological representations. To support physiological analysis, we construct and release a new multiphysiological PPG dataset with synchronized annotations for body mass index (BMI), blood pressure, blood glucose, and heart rate. Our method achieves 94.12% accuracy (F1-score: 0.93), outperforming eight state-of-the-art approaches. Further analysis reveals that BMI, blood glucose, and heart rate strongly influence identity features, highlighting the need for physiologically aware modeling in sensor systems. The proposed framework enhances PPG sensor signal interpretation, offering a scalable solution for real-time biometric sensing applications.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 8","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"SSPP-SIW Integrated Microwave Bandpass Filtering Sensor for 3-D Printed Material Real-Permittivity Characterization","authors":"Xin Zhou;Liang Yue;Chaoyu Jiang;Kam-Weng Tam;Gang Zhang;Zhuowei Zhang;Chi-Hou Chio;Dong Pan;Tuan Guo","doi":"10.1109/LSENS.2025.3590238","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3590238","url":null,"abstract":"This work presents a novel microwave sensor device for selec- tive quantification of material permittivity (<italic>ϵ</i><sub>r</sub>′) through spoof surface plasmon polariton (SSPP)-substrate integrated waveguide (SIW) integration. The proposed sensor innovatively converts dielectric property variations into measurable microwave signals via a unique transduction mechanism: passband bandwidth modulation directly controlled by <italic>ϵ</i><sub>r</sub>′. Specifically, the upper cutoff frequency shift in the SSPP-SIW sensor device serves as the sensing parameter, establishing a direct correspondence (399.3 MHz/unit <italic>ϵ</i><sub>r</sub>′) between electrical response and material dielectric properties. Compared to conventional permittivity measurement techniques, this design achieves enhanced sensitivity through SSPP field confinement while maintaining compatibility with standard microwave systems. Experimental validation demonstrates dual-functional operation as both sensor and filter, with particular effectiveness in real-time dielectric characterization of 3D-printed microwave components.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 8","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Point Cloud-Based 3-D Tracking for Asynchronous and Uncalibrated Multicamera Systems","authors":"Junhao Li;Kohei Shimasaki;Feiyue Wang;Idaku Ishii","doi":"10.1109/LSENS.2025.3590157","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3590157","url":null,"abstract":"Accurate 3-D tracking in heterogeneous, unsynchronized multicamera systems remains challenging because of calibration overhead and temporal drift. In this study, we present a point cloud- based framework that reconstructs the target trajectories without prior calibration or hardware synchronization. A sparse environmental point cloud provides a stable spatial reference; camera poses are estimated using perspective-n-point and refined with bundle adjustment. Moving objects are detected through k-nearest neighbor foreground extraction, and 2-D tracks are compressed into 1-D motion signals. Variational mode decomposition suppresses noise, whereas a two step alignment—subsequence dynamic time warping followed by sliding window fine matching—synchronizes asynchronous video streams. Robust triangulation recovers 3-D path. This method offers a low cost and easily deployable solution for wide area multitarget monitoring.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 9","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144853070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"SMA-Coated Bimorph Integrated Approach Toward Temperature Sensing Using Optical Fiber","authors":"Navneet Chouhan;Nandini Patra;Iyamperumal Anand Palani;Vipul Singh","doi":"10.1109/LSENS.2025.3589437","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3589437","url":null,"abstract":"A novel bimorph-integrated-optical fiber structure has been proposed for sensing the temperature with linearity within a broad range. Shape memory alloy-coated Kapton-polyimide sheet was used as a bimorph. Its displacement with temperature rise proportionally impacts the optical signal and inculcates a linear sensing behavior in the optical fiber. Significant optical intensity changes have been recorded with good linearity within 40 °C–120 °C. Sensitivity of ∼14.8 mV/ °C in martensite while ∼21.2 mV/ °C in the austenite phase transition range was observed with an accuracy error of ±0.014 °C. Linear intensity changes were also confirmed from the spectral analysis within two regions, however, there was a sharp deflection in wavelength of ∼1.6 nm. The technology offers an economical sensing solution with the potential for integration with the Internet of Things. It has capability for smart sensing, thereby serving contemporary industrial requirements.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 9","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144880441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Neil Joshua Limbaga;Haozheng He;José Ilton de Oliveira Filho;Khaled Nabil Salama
{"title":"Cross-Sensor Transferability of a Deep Residual U-Net for Sleep Staging Using Temporal Low-Frequency Photoplethysmography","authors":"Neil Joshua Limbaga;Haozheng He;José Ilton de Oliveira Filho;Khaled Nabil Salama","doi":"10.1109/LSENS.2025.3589877","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3589877","url":null,"abstract":"Wearable sensors are increasingly used for sleep monitoring, but accurate sleep staging often depends on expensive, high-fidelity devices and hand-crafted features. This work explores whether deep learning models trained on raw, temporal photoplethysmography (PPG) signals can generalize, not only across subjects but also across different sensors. The first phase of the study involved training a residual U-Net architecture on a large-scale sleep dataset to classify sleep stages (light, deep, and rapid eye movement (REM)). A two-stage hyperparameter sweep yielded a best test F1 score of 0.805. The second phase of the study introduced a cross-sensor transfer learning paradigm using proprietary raw PPG data labeled via a commercial wearable. Transfer learning was performed across four PPG channels; namely, Green, Green2, Red, and IR, yielding F1 scores of 0.901, 0.877, 0.892, and 0.840, respectively. These results demonstrate the model's capacity to adapt across distinct PPG configurations, supporting scalable and sensor-agnostic sleep staging.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 8","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Highly Sensitive Chemiresistive Sensor Based on Hydrothermally Synthesized ZnO Nanorods for Detection of Volatile Organic Compounds Associated With Breast Cancer","authors":"Vijay Kakarla;Aniruddh Bahadur Yadav;Rahul Checker","doi":"10.1109/LSENS.2025.3589622","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3589622","url":null,"abstract":"In this study, zinc oxide (ZnO) nanorods were synthesized using a hydrothermal method and precisely drop-coated onto an interdigitated electrode as sensing material for detecting breast cancer associated volatile organic compounds, such as heptanal and 2-propanol. The synthesized ZnO nanorods were characterized using X-ray diffraction, scanning electron micro- scopy (SEM), UV–visible spectroscopy, and energy-dispersive X-ray spectroscopy to analyze their structural properties, surface morphology, optical behavior, and elemental composition. The sensor demonstrated excellent sensitivity, strong linearity, and reliable repeatability in its detection performance. To the best of the authors' knowledge, this is the first report on the use of ZnO nanorods for the detection of breast cancer-associated volatile organic compounds, such as heptanal and 2-propanol.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 8","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144782078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Noncontact Heart Rate Measurement in Walking Rats","authors":"YuKe He;Yong Lv;Jingjing Zhang","doi":"10.1109/LSENS.2025.3588118","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3588118","url":null,"abstract":"Animal research provides experimental models that recapitulate various physiological and pathophysiological processes in humans, which are crucial for scientific breakthroughs in medicine and biology. In order to adhere to the principles of the replacement, reduction, and refinement, this work proposed a noncontact heart rate measurement approach in walking rats, using a fusion method of deep learning and signal processing. The approach uses the movement of the rat's dorsal and ventral fur regions to extract the heart rate signals. The extracted signal removes rigid motion primarily based on the spinal signal, and then obtains a clean heart rate signal by removing nonrigid motion through canonical correlation analysis. The results were highly consistent with the reference method (semi-implantable electrocardiogram), with a mean absolute percentage error of 2.09% for rats. Current research suggests that camera-based technology has great potential for measuring the heart rate of walking animals, helping to develop new methods for continuous and objective assessment of animal welfare, thereby advancing modern biomedical and ethical research.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 8","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}