Sensors

5 pages, 168 KiB

Open AccessEditorial

Artificial Intelligence and Deep Learning in Sensors and Applications

by Shyan-Ming Yuan, Zeng-Wei Hong and Wai-Khuen Cheng

Sensors 2024, 24(10), 3258; https://doi.org/10.3390/s24103258 - 20 May 2024

Cited by 1 | Viewed by 1281

To effectively solve the increasingly complex problems experienced by human beings, the latest development trend is to apply a large number of different types of sensors to collect data in order to establish effective solutions based on deep learning and artificial intelligence [...] [...] Read more.

To effectively solve the increasingly complex problems experienced by human beings, the latest development trend is to apply a large number of different types of sensors to collect data in order to establish effective solutions based on deep learning and artificial intelligence [...] Full article

(This article belongs to the Special Issue Artificial Intelligence and Deep Learning in Sensors and Applications)

7 pages, 186 KiB

Open AccessEditorial

Plasma Diagnostics

by Bruno Gonçalves

Sensors 2024, 24(10), 3257; https://doi.org/10.3390/s24103257 - 20 May 2024

Viewed by 923

Abstract

Plasma science and engineering is a multidisciplinary area encompassing some of the most exciting fundamental and applied research themes in today’s scientific landscape, with an extraordinarily broad impact in science, technology, and industry [...] Full article

(This article belongs to the Special Issue Plasma Diagnostics)

14 pages, 3558 KiB

Open AccessArticle

Reliability and Validity of the Strain Gauge “GSTRENGTH” for Measuring Peak Force in the Isometric Belt Squat at Different Joint Angles

by Daniel Varela-Olalla, Carlos Balsalobre-Fernández, Blanca Romero-Moraleda and Sergio L. Jiménez-Sáiz

Sensors 2024, 24(10), 3256; https://doi.org/10.3390/s24103256 - 20 May 2024

Viewed by 988

Abstract

Since isometric training is gaining popularity, some devices are being developed to test isometric force as an alternative to the more expensive force plates (FPs); thus, the aim of this study was to test the reliability and validity of “GSTRENGTH” for measuring PF [...] Read more.

Since isometric training is gaining popularity, some devices are being developed to test isometric force as an alternative to the more expensive force plates (FPs); thus, the aim of this study was to test the reliability and validity of “GSTRENGTH” for measuring PF in the isometric belt squat exercise. Five subjects performed 24 contractions at three different knee angles (90°, 105° and 120°) on two occasions (120 total cases). Peak force data were measured using FPs and a strain gauge (SG) and analyzed by Pearson’s product–moment correlation coefficient, ICCs, Cronbach’s alpha, a paired sample t-test and Bland–Altman plots. Perfect or almost perfect relationships (r: 0.999–1) were found with an almost perfect or perfect level of agreement (ICCs: 0.992–1; α: 0.998–1). The t-test showed significant differences for the raw data but not for the predictions by the equations obtained with the SG values. The Bland–Altman plots, when significant, showed trivial to moderate values for systematic bias in general. In conclusion, “GSTRENGTH” was shown to be a valid alternative to FPs for measuring PF. Full article

(This article belongs to the Special Issue Sports Sensors for Athlete Motion Tracking and Physiological Monitoring)

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23 pages, 12038 KiB

Open AccessArticle

Research on Assimilation of Unmanned Aerial Vehicle Remote Sensing Data and AquaCrop Model

by Wei Li, Manpeng Li, Muhammad Awais, Leilei Ji, Haoming Li, Rui Song, Muhammad Jehanzeb Masud Cheema and Ramesh Agarwal

Sensors 2024, 24(10), 3255; https://doi.org/10.3390/s24103255 - 20 May 2024

Viewed by 1056

Abstract

Taking the AquaCrop crop model as the research object, considering the complexity and uncertainty of the crop growth process, the crop model can only achieve more accurate simulation on a single point scale. In order to improve the application scale of the crop [...] Read more.

Taking the AquaCrop crop model as the research object, considering the complexity and uncertainty of the crop growth process, the crop model can only achieve more accurate simulation on a single point scale. In order to improve the application scale of the crop model, this study inverted the canopy coverage of a tea garden based on UAV multispectral technology, adopted the particle swarm optimization algorithm to assimilate the canopy coverage and crop model, constructed the AquaCrop-PSO assimilation model, and compared the canopy coverage and yield simulation results with the localized model simulation results. It is found that there is a significant regression relationship between all vegetation indices and canopy coverage. Among the single vegetation index regression models, the logarithmic model constructed by OSAVI has the highest inversion accuracy, with an R² of 0.855 and RMSE of 5.75. The tea yield was simulated by the AquaCrop-PSO model and the measured values of R² and RMSE were 0.927 and 0.12, respectively. The canopy coverage R² of each simulated growth period basically exceeded 0.9, and the accuracy of the simulation results was improved by about 19.8% compared with that of the localized model. The results show that the accuracy of crop model simulation can be improved effectively by retrieving crop parameters and assimilating crop models through UAV remote sensing. Full article

(This article belongs to the Collection Sensors and Robotics for Digital Agriculture)

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20 pages, 13727 KiB

Open AccessArticle

Design and Implementation of a Low-Cost Intelligent Unmanned Surface Vehicle

by Piyabhum Chaysri, Christos Spatharis, Kostas Vlachos and Konstantinos Blekas

Sensors 2024, 24(10), 3254; https://doi.org/10.3390/s24103254 - 20 May 2024

Cited by 1 | Viewed by 1231

Abstract

This article describes the design and construction journey of a self-developed unmanned surface vehicle (USV). In order to increase the accessibility and lower the barrier of entry we propose a low-cost (under EUR 1000) approach to the vessel construction with great adaptability and [...] Read more.

This article describes the design and construction journey of a self-developed unmanned surface vehicle (USV). In order to increase the accessibility and lower the barrier of entry we propose a low-cost (under EUR 1000) approach to the vessel construction with great adaptability and customizability. This design prioritizes minimal power consumption as a key objective. It focuses on elucidating the intricacies of both the design and assembly processes involved in creating an economical USV. Utilizing easily accessible components, the boat outlined in this study has been already participated in the 1st Aegean Ro-boat Race 2023 competition and is tailored for entry into similar robotic competitions. Its primary functionalities encompass autonomous sea navigation coupled with sophisticated collision avoidance capabilities. Finally, we studied reinforcement learning strategies for constructing a robust intelligent controller for the task of USV navigation under disturbances and we show some preliminary simulation results we have obtained. Full article

(This article belongs to the Special Issue Integrated Control and Sensing Technology for Electric Vehicles)

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23 pages, 3766 KiB

Open AccessArticle

DOxy: A Dissolved Oxygen Monitoring System

by Navid Shaghaghi, Frankie Fazlollahi, Tushar Shrivastav, Adam Graham, Jesse Mayer, Brian Liu, Gavin Jiang, Naveen Govindaraju, Sparsh Garg, Katherine Dunigan and Peter Ferguson

Sensors 2024, 24(10), 3253; https://doi.org/10.3390/s24103253 - 20 May 2024

Viewed by 1362

Abstract

Dissolved Oxygen (DO) in water enables marine life. Measuring the prevalence of DO in a body of water is an important part of sustainability efforts because low oxygen levels are a primary indicator of contamination and distress in bodies of water. Therefore, aquariums [...] Read more.

Dissolved Oxygen (DO) in water enables marine life. Measuring the prevalence of DO in a body of water is an important part of sustainability efforts because low oxygen levels are a primary indicator of contamination and distress in bodies of water. Therefore, aquariums and aquaculture of all types are in need of near real-time dissolved oxygen monitoring and spend a lot of money on purchasing and maintaining DO meters that are either expensive, inefficient, or manually operated—in which case they also need to ensure that manual readings are taken frequently which is time consuming. Hence a cost-effective and sustainable automated Internet of Things (IoT) system for this task is necessary and long overdue. DOxy, is such an IoT system under research and development at Santa Clara University’s Ethical, Pragmatic, and Intelligent Computing (EPIC) Laboratory which utilizes cost-effective, accessible, and sustainable Sensing Units (SUs) for measuring the dissolved oxygen levels present in bodies of water which send their readings to a web based cloud infrastructure for storage, analysis, and visualization. DOxy’s SUs are equipped with a High-sensitivity Pulse Oximeter meant for measuring dissolved oxygen levels in human blood, not water. Hence a number of parallel readings of water samples were gathered by both the High-sensitivity Pulse Oximeter and a standard dissolved oxygen meter. Then, two approaches for relating the readings were investigated. In the first, various machine learning models were trained and tested to produce a dynamic mapping of sensor readings to actual DO values. In the second, curve-fitting models were used to produce a successful conversion formula usable in the DOxy SUs offline. Both proved successful in producing accurate results. Full article

(This article belongs to the Section Smart Agriculture)

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22 pages, 12610 KiB

Open AccessArticle

A Detection Transformer-Based Intelligent Identification Method for Multiple Types of Road Traffic Safety Facilities

by Lingxin Lu, Hui Wang, Yan Wan and Feifei Xu

Sensors 2024, 24(10), 3252; https://doi.org/10.3390/s24103252 - 20 May 2024

Viewed by 1019

Abstract

Road traffic safety facilities (TSFs) are of significant importance in the management and maintenance of traffic safety. The complexity and variety of TSFs make it challenging to detect them manually, which renders the work unsustainable. To achieve the objective of automatic TSF detection, [...] Read more.

Road traffic safety facilities (TSFs) are of significant importance in the management and maintenance of traffic safety. The complexity and variety of TSFs make it challenging to detect them manually, which renders the work unsustainable. To achieve the objective of automatic TSF detection, a target detection dataset, designated TSF-CQU (TSF data collected by Chongqing University), was constructed based on images collected by a car recorder. This dataset comprises six types of TSFs and 8410 instance samples. A detection transformer with an improved denoising anchor box (DINO) was selected to construct a model that would be suitable for this scenario. For comparison purposes, Faster R-CNN (Region Convolutional Neural Network) and Yolov7 (You Only Look Once version 7) were employed. The DINO model demonstrated the highest performance on the TSF-CQU dataset, with a mean average precision (mAP) of 82.2%. All of the average precision (AP) values exceeded 0.8, except for streetlights (AP = 0.77) and rods (AP = 0.648). The DINO model exhibits minimal instances of erroneous recognition, which substantiates the efficacy of the contrastive denoising training approach. The DINO model rarely makes misjudgments, but a few missed detection. Full article

(This article belongs to the Special Issue Toward Green and Intelligent Transportation Infrastructure: Road Non-destructive Testing and Structural Health Monitoring Technologies)

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24 pages, 36155 KiB

Open AccessArticle

Heavy Metal Concentration Estimation for Different Farmland Soils Based on Projection Pursuit and LightGBM with Hyperspectral Images

by Nan Lin, Xiaofan Shao, Huizhi Wu, Ranzhe Jiang and Menghong Wu

Sensors 2024, 24(10), 3251; https://doi.org/10.3390/s24103251 - 20 May 2024

Viewed by 871

Abstract

Heavy metal pollution in farmland soil threatens soil environmental quality. It is an important task to quickly grasp the status of heavy metal pollution in farmland soil in a region. Hyperspectral remote sensing technology has been widely used in soil heavy metal concentration [...] Read more.

Heavy metal pollution in farmland soil threatens soil environmental quality. It is an important task to quickly grasp the status of heavy metal pollution in farmland soil in a region. Hyperspectral remote sensing technology has been widely used in soil heavy metal concentration monitoring. How to improve the accuracy and reliability of its estimation model is a hot topic. This study analyzed 440 soil samples from Sihe Town and the surrounding agricultural areas in Yushu City, Jilin Province. Considering the differences between different types of soils, a local regression model of heavy metal concentrations (As and Cu) was established based on projection pursuit (PP) and light gradient boosting machine (LightGBM) algorithms. Based on the estimations, a spatial distribution map of soil heavy metals in the region was drawn. The findings of this study showed that considering the differences between different soils to construct a local regression estimation model of soil heavy metal concentration improved the estimation accuracy. Specifically, the relative percent difference (RPD) of As and Cu element estimations in black soil increased the most, by 0.30 and 0.26, respectively. The regional spatial distribution map of heavy metal concentration derived from local regression showed high spatial variability. The number of characteristic bands screened by the PP method accounted for 10–13% of the total spectral bands, effectively reducing the model complexity. Compared with the traditional machine model, the LightGBM model showed better estimation ability, and the highest determination coefficients (R²) of different soil validation sets reached 0.73 (As) and 0.75 (Cu), respectively. In this study, the constructed PP–LightGBM estimation model takes into account the differences in soil types, which effectively improves the accuracy and reliability of hyperspectral image estimation of soil heavy metal concentration and provides a reference for drawing large-scale spatial distributions of heavy metals from hyperspectral images and mastering soil environmental quality. Full article

(This article belongs to the Special Issue Methodologies Used in Hyperspectral Remote Sensing in Agriculture)

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13 pages, 1445 KiB

Open AccessArticle

Silicon Microring Resonator Biosensor for Detection of Nucleocapsid Protein of SARS-CoV-2

by Yusuke Uchida, Taro Arakawa, Akio Higo and Yuhei Ishizaka

Sensors 2024, 24(10), 3250; https://doi.org/10.3390/s24103250 - 20 May 2024

Cited by 1 | Viewed by 1171

Abstract

A high-sensitivity silicon microring (Si MRR) optical biosensor for detecting the nucleocapsid protein of SARS-CoV-2 is proposed and demonstrated. In the proposed biosensor, the surface of a Si MRR waveguide is modified with antibodies, and the target protein is detected by measuring a [...] Read more.

A high-sensitivity silicon microring (Si MRR) optical biosensor for detecting the nucleocapsid protein of SARS-CoV-2 is proposed and demonstrated. In the proposed biosensor, the surface of a Si MRR waveguide is modified with antibodies, and the target protein is detected by measuring a resonant wavelength shift of the MRR caused by the selective adsorption of the protein to the surface of the waveguide. A Si MRR is fabricated on a silicon-on-insulator substrate using a CMOS-compatible fabrication process. The quality factor of the MRR is approximately 20,000. The resonant wavelength shift of the MRR and the detection limit for the environmental refractive index change are evaluated to be 89 nm/refractive index unit (RIU) and 10⁻⁴ RIU, respectively. The sensing characteristics are examined using a polydimethylsiloxane flow channel after the surface of the Si MRR waveguide is modified with the IgG antibodies through the Si-tagged protein. First, the selective detection of the protein by the MRR sensor is experimentally demonstrated by the detection of bovine serum albumin and human serum albumin. Next, various concentrations of nucleocapsid protein solutions are measured by the MRR, in which the waveguide surface is modified with the IgG antibodies through the Si-tagged protein. Although the experimental results are very preliminary, they show that the proposed sensor has a potential nucleocapsid sensitivity in the order of 10 pg/mL, which is comparable to the sensitivity of current antigen tests. The detection time is less than 10 min, which is much shorter than those of other antigen tests. Full article

(This article belongs to the Section Biosensors)

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14 pages, 3111 KiB

Open AccessArticle

Cost-Effective Optical Wireless Sensor Networks: Enhancing Detection of Sub-Pixel Transmitters in Camera-Based Communications

by Idaira Rodríguez-Yánez, Víctor Guerra, José Rabadán and Rafael Pérez-Jiménez

Sensors 2024, 24(10), 3249; https://doi.org/10.3390/s24103249 - 20 May 2024

Viewed by 828

Abstract

In the domain of the Internet of Things (IoT), Optical Camera Communication (OCC) has garnered significant attention. This wireless technology employs solid-state lamps as transmitters and image sensors as receivers, offering a promising avenue for reducing energy costs and simplifying electronics. Moreover, image [...] Read more.

In the domain of the Internet of Things (IoT), Optical Camera Communication (OCC) has garnered significant attention. This wireless technology employs solid-state lamps as transmitters and image sensors as receivers, offering a promising avenue for reducing energy costs and simplifying electronics. Moreover, image sensors are prevalent in various applications today, enabling dual functionality: recording and communication. However, a challenge arises when optical transmitters are not in close proximity to the camera, leading to sub-pixel projections on the image sensor and introducing strong channel dependence. Previous approaches, such as modifying camera optics or adjusting image sensor parameters, not only limited the camera’s utility for purposes beyond communication but also made it challenging to accommodate multiple transmitters. In this paper, a novel sub-pixel optical transmitter discovery algorithm that overcomes these limitations is presented. This algorithm enables the use of OCC in scenarios with static transmitters and receivers without the need for camera modifications. This allows increasing the number of transmitters in a given scenario and alleviates the proximity and size limitations of the transmitters. Implemented in Python with multiprocessing programming schemes for efficiency, the algorithm achieved a 100% detection rate in nighttime scenarios, while there was a 89% detection rate indoors and a 72% rate outdoors during daylight. Detection rates were strongly influenced by varying transmitter types and lighting conditions. False positives remained minimal, and processing times were consistently under 1 s. With these results, the algorithm is considered suitable for export as a web service or as an intermediary component for data conversion into other network technologies. Full article

(This article belongs to the Special Issue Lighting Up Wireless Communication, Sensing and Power Delivery)

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17 pages, 6505 KiB

Open AccessArticle

Analysis of E2E Delay and Wiring Harness in In-Vehicle Network with Zonal Architecture

by Chulsun Park, Chengyu Cui and Sungkwon Park

Sensors 2024, 24(10), 3248; https://doi.org/10.3390/s24103248 - 20 May 2024

Viewed by 877

Abstract

With recent advances in vehicle technologies, in-vehicle networks (IVNs) and wiring harnesses are becoming increasingly complex. To solve these challenges, the automotive industry has adopted a new zonal-based IVN architecture (ZIA) that connects electronic control units (ECUs) according to their physical locations. In [...] Read more.

With recent advances in vehicle technologies, in-vehicle networks (IVNs) and wiring harnesses are becoming increasingly complex. To solve these challenges, the automotive industry has adopted a new zonal-based IVN architecture (ZIA) that connects electronic control units (ECUs) according to their physical locations. In this paper, we evaluate how the number of zones in the ZIA affects the end-to-end (E2E) delay and the characteristics of the wiring harnesses. We evaluate the impact of the number of zones on E2E delay through the OMNeT++ network simulator. In addition, we theoretically predict and analyze the impact of the number of zones on the wiring harnesses. Specifically, we use an asymptotic approach to analyze the total length and weight evolution of the wiring harnesses in ZIAs with 2, 4, 6, 8, and 10 zones by incrementally increasing the number of ECUs. We find that as the number of zones increases, the E2E delay increases, but the total length and weight of the wiring harnesses decreases. These results confirm that the ZIA effectively uses the wiring harnesses and mitigates network complexity within the vehicle. Full article

(This article belongs to the Section Vehicular Sensing)

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32 pages, 10794 KiB

Open AccessArticle

Improving the Concrete Crack Detection Process via a Hybrid Visual Transformer Algorithm

by Mohammad Shahin, F. Frank Chen, Mazdak Maghanaki, Ali Hosseinzadeh, Neda Zand and Hamid Khodadadi Koodiani

Sensors 2024, 24(10), 3247; https://doi.org/10.3390/s24103247 - 20 May 2024

Cited by 3 | Viewed by 1600

Abstract

Inspections of concrete bridges across the United States represent a significant commitment of resources, given their biannual mandate for many structures. With a notable number of aging bridges, there is an imperative need to enhance the efficiency of these inspections. This study harnessed [...] Read more.

Inspections of concrete bridges across the United States represent a significant commitment of resources, given their biannual mandate for many structures. With a notable number of aging bridges, there is an imperative need to enhance the efficiency of these inspections. This study harnessed the power of computer vision to streamline the inspection process. Our experiment examined the efficacy of a state-of-the-art Visual Transformer (ViT) model combined with distinct image enhancement detector algorithms. We benchmarked against a deep learning Convolutional Neural Network (CNN) model. These models were applied to over 20,000 high-quality images from the Concrete Images for Classification dataset. Traditional crack detection methods often fall short due to their heavy reliance on time and resources. This research pioneers bridge inspection by integrating ViT with diverse image enhancement detectors, significantly improving concrete crack detection accuracy. Notably, a custom-built CNN achieves over 99% accuracy with substantially lower training time than ViT, making it an efficient solution for enhancing safety and resource conservation in infrastructure management. These advancements enhance safety by enabling reliable detection and timely maintenance, but they also align with Industry 4.0 objectives, automating manual inspections, reducing costs, and advancing technological integration in public infrastructure management. Full article

(This article belongs to the Section Fault Diagnosis & Sensors)

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18 pages, 8250 KiB

Open AccessArticle

Single-Shot 3D Reconstruction via Nonlinear Fringe Transformation: Supervised and Unsupervised Learning Approaches

by Andrew-Hieu Nguyen and Zhaoyang Wang

Sensors 2024, 24(10), 3246; https://doi.org/10.3390/s24103246 - 20 May 2024

Viewed by 1129

Abstract

The field of computer vision has been focusing on achieving accurate three-dimensional (3D) object representations from a single two-dimensional (2D) image through deep artificial neural networks. Recent advancements in 3D shape reconstruction techniques that combine structured light and deep learning show promise in [...] Read more.

The field of computer vision has been focusing on achieving accurate three-dimensional (3D) object representations from a single two-dimensional (2D) image through deep artificial neural networks. Recent advancements in 3D shape reconstruction techniques that combine structured light and deep learning show promise in acquiring high-quality geometric information about object surfaces. This paper introduces a new single-shot 3D shape reconstruction method that uses a nonlinear fringe transformation approach through both supervised and unsupervised learning networks. In this method, a deep learning network learns to convert a grayscale fringe input into multiple phase-shifted fringe outputs with different frequencies, which act as an intermediate result for the subsequent 3D reconstruction process using the structured-light fringe projection profilometry technique. Experiments have been conducted to validate the practicality and robustness of the proposed technique. The experimental results demonstrate that the unsupervised learning approach using a deep convolutional generative adversarial network (DCGAN) is superior to the supervised learning approach using UNet in image-to-image generation. The proposed technique’s ability to accurately reconstruct 3D shapes of objects using only a single fringe image opens up vast opportunities for its application across diverse real-world scenarios. Full article

(This article belongs to the Special Issue Stereo Vision Sensing and Image Processing)

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(A) Flowchart of the proposed nonlinear fringe transformation for 3D reconstruction; (B) dual-frequency nonlinear transformation; (C) triple-frequency nonlinear transformation. Full article ">Figure 2
Diagram illustrating the fringe projection profilometry method using a dual-frequency four-step phase-shifting approach. Full article ">Figure 3
Illustration of the input–output pairs used for training within the datasets employing the DFFS scheme. Full article ">Figure 4
Architecture of the supervised UNet (A) and unsupervised DCGAN (B) models utilized in the training process. Full article ">Figure 5
Assessment of image quality using the SSIM and PSNR metrics for predicted fringe images. Full article ">Figure 6
Comparison of the 3D reconstruction results between UNet and DCGAN models when utilizing the DFFS scheme. Full article ">Figure 7
Comparison of 3D reconstruction using distinct fringe inputs at frequencies <math display="inline"><semantics> <mrow> <mi>f</mi> <mo>=</mo> <mn>79</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>f</mi> <mo>=</mo> <mn>80</mn> </mrow> </semantics></math>. Full article ">Figure 8
Visualization of 3D reconstruction in single-object scenes utilizing the TFFS scheme. Full article ">

15 pages, 3017 KiB

Open AccessArticle

Examining the Effects of Altitude on Workload Demands in Professional Basketball Players during the Preseason Phase

by Sergio J. Ibáñez, Carlos D. Gómez-Carmona, Sergio González-Espinosa and David Mancha-Triguero

Sensors 2024, 24(10), 3245; https://doi.org/10.3390/s24103245 - 20 May 2024

Viewed by 1070

Abstract

Basketball involves frequent high-intensity movements requiring optimal aerobic power. Altitude training can enhance physiological adaptations, but research examining its effects in basketball is limited. This study aimed to characterize the internal/external workload of professional basketball players during preseason and evaluate the effects of [...] Read more.

Basketball involves frequent high-intensity movements requiring optimal aerobic power. Altitude training can enhance physiological adaptations, but research examining its effects in basketball is limited. This study aimed to characterize the internal/external workload of professional basketball players during preseason and evaluate the effects of altitude and playing position. Twelve top-tier professional male basketball players (Liga Endesa, ACB; guards: n = 3, forwards: n = 5, and centers: n = 4) participated in a crossover study design composed of two training camps with nine sessions over 6 days under two different conditions: high altitude (2320 m) and sea level (10 m). Internal loads (heart rate, %HR_MAX) and external loads (total distances covered across speed thresholds, accelerations/decelerations, impacts, and jumps) were quantified via wearable tracking and heart rate telemetry. Repeated-measures MANOVA tested the altitude x playing position effects. Altitude increased the total distance (+10%), lower-speed running distances (+10–39%), accelerations/decelerations (+25–30%), average heart rate (+6%), time in higher-intensity HR zones (+23–63%), and jumps (+13%) across all positions (p < 0.05). Positional differences existed, with guards accruing more high-speed running and centers exhibiting greater cardiovascular demands (p < 0.05). In conclusion, a 6-day altitude block effectively overloads training, providing a stimulus to enhance fitness capacities when structured appropriately. Monitoring workloads and individualizing training by playing position are important when implementing altitude training, given the varied responses. Full article

(This article belongs to the Special Issue Artificial Intelligence (AI) and Sensors in Sports Safety and NextGen Rehabilitation)

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25 pages, 4459 KiB

Open AccessArticle

RI2AP: Robust and Interpretable 2D Anomaly Prediction in Assembly Pipelines

by Chathurangi Shyalika, Kaushik Roy, Renjith Prasad, Fadi El Kalach, Yuxin Zi, Priya Mittal, Vignesh Narayanan, Ramy Harik and Amit Sheth

Sensors 2024, 24(10), 3244; https://doi.org/10.3390/s24103244 - 20 May 2024

Viewed by 1254

Abstract

Predicting anomalies in manufacturing assembly lines is crucial for reducing time and labor costs and improving processes. For instance, in rocket assembly, premature part failures can lead to significant financial losses and labor inefficiencies. With the abundance of sensor data in the Industry [...] Read more.

Predicting anomalies in manufacturing assembly lines is crucial for reducing time and labor costs and improving processes. For instance, in rocket assembly, premature part failures can lead to significant financial losses and labor inefficiencies. With the abundance of sensor data in the Industry 4.0 era, machine learning (ML) offers potential for early anomaly detection. However, current ML methods for anomaly prediction have limitations, with F1 measure scores of only 50% and 66% for prediction and detection, respectively. This is due to challenges like the rarity of anomalous events, scarcity of high-fidelity simulation data (actual data are expensive), and the complex relationships between anomalies not easily captured using traditional ML approaches. Specifically, these challenges relate to two dimensions of anomaly prediction: predicting when anomalies will occur and understanding the dependencies between them. This paper introduces a new method called Robust and Interpretable 2D Anomaly Prediction (RI2AP) designed to address both dimensions effectively. RI2AP is demonstrated on a rocket assembly simulation, showing up to a 30-point improvement in F1 measure compared to current ML methods. This highlights its potential to enhance automated anomaly prediction in manufacturing. Additionally, RI2AP includes a novel interpretation mechanism inspired by a causal-influence framework, providing domain experts with valuable insights into sensor readings and their impact on predictions. Finally, the RI2AP model was deployed in a real manufacturing setting for assembling rocket parts. Results and insights from this deployment demonstrate the promise of RI2AP for anomaly prediction in manufacturing assembly pipelines. Full article

(This article belongs to the Special Issue Industrial Sensor Enabled Smart Computing for Design, Control and Maintenance in Real Time Applications)

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26 pages, 8206 KiB

Open AccessArticle

Mathematical Physics Analysis of Nozzle Shaping at the Gas Outlet from the Aperture to the Differentially Pumped Chamber in Environmental Scanning Electron Microscopy (ESEM)

by Jiří Maxa, Vilém Neděla, Pavla Šabacká and Tomáš Binar

Sensors 2024, 24(10), 3243; https://doi.org/10.3390/s24103243 - 20 May 2024

Viewed by 719

Abstract

A combination of experimental measurement preparations using pressure and temperature sensors in conjunction with the theory of one-dimensional isentropic flow and mathematical physics analyses is presented as a tool for analysis in this paper. Furthermore, the subsequent development of a nozzle for use [...] Read more.

A combination of experimental measurement preparations using pressure and temperature sensors in conjunction with the theory of one-dimensional isentropic flow and mathematical physics analyses is presented as a tool for analysis in this paper. Furthermore, the subsequent development of a nozzle for use in environmental electron microscopy between the specimen chamber and the differentially pumped chamber is described. Based on experimental measurements, an analysis of the impact of the nozzle shaping located behind the aperture on the character of the supersonic flow and the resulting dispersion of the electron beam passing through the differential pumped chamber is carried out on the determined pressure ratio using a combination of theory and mathematical physics analyses. The results show that nozzle shapes causing under-expanded gas outflow from the aperture to the nozzle have a worse impact on the dispersion of the primary electron beam. This is due to the flow velocity control. The controlled reduction in the static pressure curve on the primary electron beam path thus causes a significantly higher course of electron dispersion values than variants with shapes causing over-expanded gas outflow. Full article

(This article belongs to the Special Issue Advanced Sensors for Gas Monitoring)

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34 pages, 5772 KiB

Open AccessReview

A Comprehensive Overview of Network Slicing for Improving the Energy Efficiency of Fifth-Generation Networks

by Josip Lorincz, Amar Kukuruzović and Zoran Blažević

Sensors 2024, 24(10), 3242; https://doi.org/10.3390/s24103242 - 20 May 2024

Cited by 1 | Viewed by 1755

Abstract

The introduction of fifth-generation (5G) mobile networks leads to an increase in energy consumption and higher operational costs for mobile network operators (MNOs). Consequently, the optimization of 5G networks’ energy efficiency is crucial, both in terms of reducing MNO costs and in terms [...] Read more.

The introduction of fifth-generation (5G) mobile networks leads to an increase in energy consumption and higher operational costs for mobile network operators (MNOs). Consequently, the optimization of 5G networks’ energy efficiency is crucial, both in terms of reducing MNO costs and in terms of the negative environmental impact. However, many aspects of the 5G mobile network technology itself have been standardized, including the 5G network slicing concept. This enables the creation of multiple independent logical 5G networks within the same physical infrastructure. Since the only necessary resources in 5G networks need to be used for the realization of a specific 5G network slice, the question of whether the implementation of 5G network slicing can contribute to the improvement of 5G and future sixth-generation networks’ energy efficiency arises. To tackle this question, this review paper analyzes 5G network slicing and the energy demand of different network slicing use cases and mobile virtual network operator realizations based on network slicing. The paper also overviews standardized key performance indicators for the assessment of 5G network slices’ energy efficiency and discusses energy efficiency in 5G network slicing lifecycle management. In particular, to show how efficient network slicing can optimize the energy consumption of 5G networks, versatile 5G network slicing use case scenarios, approaches, and resource allocation concepts in the space, time, and frequency domains have been discussed, including artificial intelligence-based implementations of network slicing. The results of the comprehensive discussion indicate that the different implementations and approaches to network slicing pave the way for possible further reductions in 5G MNO energy costs and carbon dioxide emissions in the future. Full article

(This article belongs to the Special Issue Energy-Efficient Communication Networks and Systems: 2nd Edition)

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25 pages, 874 KiB

Open AccessArticle

PrivShieldROS: An Extended Robot Operating System Integrating Ethereum and Interplanetary File System for Enhanced Sensor Data Privacy

by Tianhao Wang, Ke Chen, Zhaohua Zheng, Jiahao Guo, Xiying Zhao and Shenhui Zhang

Sensors 2024, 24(10), 3241; https://doi.org/10.3390/s24103241 - 20 May 2024

Cited by 3 | Viewed by 1039

Abstract

With the application of robotics in security monitoring, medical care, image analysis, and other high-privacy fields, vision sensor data in robotic operating systems (ROS) faces the challenge of enhancing secure storage and transmission. Recently, it has been proposed that the distributed advantages of [...] Read more.

With the application of robotics in security monitoring, medical care, image analysis, and other high-privacy fields, vision sensor data in robotic operating systems (ROS) faces the challenge of enhancing secure storage and transmission. Recently, it has been proposed that the distributed advantages of blockchain be taken advantage of to improve the security of data in ROS. Still, it has limitations such as high latency and large resource consumption. To address these issues, this paper introduces PrivShieldROS, an extended robotic operating system developed by InterPlanetary File System (IPFS), blockchain, and HybridABEnc to enhance the confidentiality and security of vision sensor data in ROS. The system takes advantage of the decentralized nature of IPFS to enhance data availability and robustness while combining HybridABEnc for fine-grained access control. In addition, it ensures the security and confidentiality of the data distribution mechanism by using blockchain technology to store data content identifiers (CID) persistently. Finally, the effectiveness of this system is verified by three experiments. Compared with the state-of-the-art blockchain-extended ROS, PrivShieldROS shows improvements in key metrics. This paper has been partly submitted to IROS 2024. Full article

(This article belongs to the Special Issue AI-Driven Cybersecurity in IoT-Based Systems)

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The figure on the left shows the AuthROS framework, which stores data directly on the blockchain with significant resource consumption. Therefore, we adopted IPFS to store the data and store the CID of the data on the blockchain, thus greatly reducing the resource overhead of the blockchain, and the PrivShieldROS framework is shown on the right. Full article ">Figure 2
The framework of the PrivShieldROS. The system includes two parts: data processing and storage, and data acquisition and verification. Processes 1, 2, 3, and 4 involve the processing and storage of data; Processes 5, 6, and 7 are responsible for data acquisition and related validation operations. In addition, we store the mappings on the blockchain, labeled ➀, ➁, ➂, and ➃, to support the functionality of the system. The message middleware in the figure is a component that is used to process and deliver messages. In the distributed system, the message middleware acts as the bridge of message passing, which enables different components to communicate with each other asynchronously. The experimental part of rabbitMQ is a kind of message middleware. Full article ">Figure 3
Schematic diagram of KP-ABE algorithm. Full article ">Figure 4
ROS node part flow chart. Full article ">Figure 5
Smart contract part diagram. Full article ">

11 pages, 2139 KiB 5.5 Earthquakes" data-journal="sensors">

Open AccessCommunication

Refinement of Different Frequency Bands of Geomagnetic Vertical Intensity Polarization Anomalies before M > 5.5 Earthquakes

by Haris Faheem, Xia Li, Weiling Zhu, Yingfeng Ji, Lili Feng and Ye Zhu

Sensors 2024, 24(10), 3240; https://doi.org/10.3390/s24103240 - 20 May 2024

Cited by 1 | Viewed by 923

Abstract

Geomagnetic vertical intensity polarization is a method with a clear mechanism, mature processing methods, and a strong ability to extract anomalous information in the quantitative analysis of seismogenic geomagnetic disturbances. The existing analyses of geomagnetic vertical intensity polarization are all based on the [...] Read more.

Geomagnetic vertical intensity polarization is a method with a clear mechanism, mature processing methods, and a strong ability to extract anomalous information in the quantitative analysis of seismogenic geomagnetic disturbances. The existing analyses of geomagnetic vertical intensity polarization are all based on the 5~100 s frequency band without refinement of the partitioning process. Although many successful results have been obtained, there are still two problems in the process of extracting anomalies: the geomagnetic anomalies that satisfy the determination criteria are still high in occurrence frequency; and the anomalies are distributed over too large an area in space, which leads to difficulties in determining the location of the epicenter. In this study, based on observations from western China, where fluxgate observation points are positioned in areas with frequent, densely distributed medium-strength earthquakes, we refined the frequency bands of geomagnetic vertical intensity polarization, recalculated the spatial and temporal evolution characteristics of geomagnetic disturbances before earthquakes, and improved the crossover frequency anomaly prediction index while promoting the application of the method in earthquake forecasting. Full article

(This article belongs to the Collection Seismology and Earthquake Engineering)

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28 pages, 1250 KiB

Open AccessArticle

Hydrogen 4.0: A Cyber–Physical System for Renewable Hydrogen Energy Plants

by Ali Yavari, Christopher J. Harrison, Saman A. Gorji and Mahnaz Shafiei

Sensors 2024, 24(10), 3239; https://doi.org/10.3390/s24103239 - 20 May 2024

Cited by 2 | Viewed by 3741

Abstract

The demand for green hydrogen as an energy carrier is projected to exceed 350 million tons per year by 2050, driven by the need for sustainable distribution and storage of energy generated from sources. Despite its potential, hydrogen production currently faces challenges related [...] Read more.

The demand for green hydrogen as an energy carrier is projected to exceed 350 million tons per year by 2050, driven by the need for sustainable distribution and storage of energy generated from sources. Despite its potential, hydrogen production currently faces challenges related to cost efficiency, compliance, monitoring, and safety. This work proposes Hydrogen 4.0, a cyber–physical approach that leverages Industry 4.0 technologies—including smart sensing, analytics, and the Internet of Things (IoT)—to address these issues in hydrogen energy plants. Such an approach has the potential to enhance efficiency, safety, and compliance through real-time data analysis, predictive maintenance, and optimised resource allocation, ultimately facilitating the adoption of renewable green hydrogen. The following sections break down conventional hydrogen plants into functional blocks and discusses how Industry 4.0 technologies can be applied to each segment. The components, benefits, and application scenarios of Hydrogen 4.0 are discussed while how digitalisation technologies can contribute to the successful integration of sustainable energy solutions in the global energy sector is also addressed. Full article

(This article belongs to the Special Issue Smart IoT System for Renewable Energy Resource-2nd Edition)

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12 pages, 6227 KiB

Open AccessArticle

GPR Mapping of Cavities in Complex Scenarios with a Combined Time–Depth Conversion

by Raffaele Persico, Ilaria Catapano, Giuseppe Esposito, Gianfranco Morelli, Gregory De Martino and Luigi Capozzoli

Sensors 2024, 24(10), 3238; https://doi.org/10.3390/s24103238 - 20 May 2024

Viewed by 813

Abstract

The paper deals with a combined time–depth conversion strategy able to improve the reconstruction of voids embedded in an opaque medium, such as cavities, caves, empty hypogeal rooms, and similar targets. The combined time–depth conversion accounts for the propagation velocity of the electromagnetic [...] Read more.

The paper deals with a combined time–depth conversion strategy able to improve the reconstruction of voids embedded in an opaque medium, such as cavities, caves, empty hypogeal rooms, and similar targets. The combined time–depth conversion accounts for the propagation velocity of the electromagnetic waves both in free space and in the embedding medium, and it allows better imaging and interpretation of the underground scenario. To assess the strategy’s effectiveness, ground penetrating radar (GPR) data referred to as an experimental test in controlled conditions are accounted for and processed by two different approaches to achieve focused images of the scenario under test. The first approach is based on a classical migration algorithm, while the second one faces the imaging as a linear inverse scattering approach. The results corroborate that the combined time–depth conversion improves the imaging in both cases. Full article

(This article belongs to the Special Issue Sensors and Sensing Technologies for Archaeological and Cultural Heritage Evaluation)

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14 pages, 652 KiB

Open AccessArticle

Antijamming Schemes for the Generalized MIMO Y Channel

by Karolina Lenarska and Krzysztof Wesołowski

Sensors 2024, 24(10), 3237; https://doi.org/10.3390/s24103237 - 20 May 2024

Viewed by 673

Abstract

Signal space alignment (SSA) is a promising technique for interference management in wireless networks. However, despite the excellent work done on SSA, its robustness against jamming attacks has not been considered in the literature. In this paper, we propose two antijamming strategies for [...] Read more.

Signal space alignment (SSA) is a promising technique for interference management in wireless networks. However, despite the excellent work done on SSA, its robustness against jamming attacks has not been considered in the literature. In this paper, we propose two antijamming strategies for the SSA scheme applied in the multiple-input–multiple-output (MIMO) Y channel. The first scheme involves projecting the jamming signal into the null space of each source’s precoding vectors, effectively eliminating it entirely. The second scheme removes interference originating from the jammer by subtracting the disturbance estimate from the incoming signal. The estimate is derived on the basis of the criterion of minimizing the received signal energy. The block error rate (BLER) performance of the proposed strategies in various channel configurations is verified by link level simulations and is presented to show the efficiency in mitigating jamming signals within the SSA-based MIMO Y channel. Full article

(This article belongs to the Section Communications)

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19 pages, 4309 KiB

Open AccessArticle

Deep Anomaly Detection Framework Utilizing Federated Learning for Electricity Theft Zero-Day Cyberattacks

by Ali Alshehri, Mahmoud M. Badr, Mohamed Baza and Hani Alshahrani

Sensors 2024, 24(10), 3236; https://doi.org/10.3390/s24103236 - 20 May 2024

Cited by 2 | Viewed by 1207

Abstract

Smart power grids suffer from electricity theft cyber-attacks, where malicious consumers compromise their smart meters (SMs) to downscale the reported electricity consumption readings. This problem costs electric utility companies worldwide considerable financial burdens and threatens power grid stability. Therefore, several machine learning (ML)-based [...] Read more.

Smart power grids suffer from electricity theft cyber-attacks, where malicious consumers compromise their smart meters (SMs) to downscale the reported electricity consumption readings. This problem costs electric utility companies worldwide considerable financial burdens and threatens power grid stability. Therefore, several machine learning (ML)-based solutions have been proposed to detect electricity theft; however, they have limitations. First, most existing works employ supervised learning that requires the availability of labeled datasets of benign and malicious electricity usage samples. Unfortunately, this approach is not practical due to the scarcity of real malicious electricity usage samples. Moreover, training a supervised detector on specific cyberattack scenarios results in a robust detector against those attacks, but it might fail to detect new attack scenarios. Second, although a few works investigated anomaly detectors for electricity theft, none of the existing works addressed consumers’ privacy. To address these limitations, in this paper, we propose a comprehensive federated learning (FL)-based deep anomaly detection framework tailored for practical, reliable, and privacy-preserving energy theft detection. In our proposed framework, consumers train local deep autoencoder-based detectors on their private electricity usage data and only share their trained detectors’ parameters with an EUC aggregation server to iteratively build a global anomaly detector. Our extensive experimental results not only demonstrate the superior performance of our anomaly detector compared to the supervised detectors but also the capability of our proposed FL-based anomaly detector to accurately detect zero-day attacks of electricity theft while preserving consumers’ privacy. Full article

(This article belongs to the Special Issue Cybersecurity Issues in Smart Grids and Future Power Systems—2nd Edition)

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25 pages, 3407 KiB

Open AccessReview

Radiation Damage Mechanisms and Research Status of Radiation-Resistant Optical Fibers: A Review

by Jicong Li, Qi Chen, Jia Zhou, Zhi Cao, Tianchi Li, Fang Liu, Zhongyuan Yang, Shangwen Chang, Keyuan Zhou, Yuzhou Ming, Taihong Yan and Weifang Zheng

Sensors 2024, 24(10), 3235; https://doi.org/10.3390/s24103235 - 20 May 2024

Cited by 1 | Viewed by 1959

Abstract

In recent years, optical fibers have found extensive use in special environments, including high-energy radiation scenarios like nuclear explosion diagnostics and reactor monitoring. However, radiation exposure, such as X-rays, gamma rays, and neutrons, can compromise fiber safety and reliability. Consequently, researchers worldwide are [...] Read more.

In recent years, optical fibers have found extensive use in special environments, including high-energy radiation scenarios like nuclear explosion diagnostics and reactor monitoring. However, radiation exposure, such as X-rays, gamma rays, and neutrons, can compromise fiber safety and reliability. Consequently, researchers worldwide are focusing on radiation-resistant fiber optic technology. This paper examines optical fiber radiation damage mechanisms, encompassing ionization damage, displacement damage, and defect centers. It also surveys the current research on radiation-resistant fiber optic design, including doping and manufacturing process improvements. Ultimately, it summarizes the effectiveness of various approaches and forecasts the future of radiation-resistant optical fibers. Full article

(This article belongs to the Special Issue Specialty Optical Fibers: Advance and Sensing Application)

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18 pages, 4076 KiB

Open AccessArticle

Research on a Wind Turbine Gearbox Fault Diagnosis Method Using Singular Value Decomposition and Graph Fourier Transform

by Lan Chen, Xiangfeng Zhang, Zhanxiang Li and Hong Jiang

Sensors 2024, 24(10), 3234; https://doi.org/10.3390/s24103234 - 20 May 2024

Cited by 1 | Viewed by 1024

Abstract

Gearboxes operate in challenging environments, which leads to a heightened incidence of failures, and ambient noise further compromises the accuracy of fault diagnosis. To address this issue, we introduce a fault diagnosis method that employs singular value decomposition (SVD) and graph Fourier transform [...] Read more.

Gearboxes operate in challenging environments, which leads to a heightened incidence of failures, and ambient noise further compromises the accuracy of fault diagnosis. To address this issue, we introduce a fault diagnosis method that employs singular value decomposition (SVD) and graph Fourier transform (GFT). Singular values, commonly employed in feature extraction and fault diagnosis, effectively encapsulate various fault states of mechanical equipment. However, prior methods neglect the inter-relationships among singular values, resulting in the loss of subtle fault information concealed within. To precisely and effectively extract subtle fault information from gear vibration signals, this study incorporates graph signal processing (GSP) technology. Following SVD of the original vibration signal, the method constructs a graph signal using singular values as inputs, enabling the capture of topological relationships among these values and the extraction of concealed fault information. Subsequently, the graph signal undergoes a transformation via GFT, facilitating the extraction of fault features from the graph spectral domain. Ultimately, by assessing the Mahalanobis distance between training and testing samples, distinct defect states are discerned and diagnosed. Experimental results on bearing and gear faults demonstrate that the proposed method exhibits enhanced robustness to noise, enabling accurate and effective diagnosis of gearbox faults in environments with substantial noise. Full article

(This article belongs to the Section Fault Diagnosis & Sensors)

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14 pages, 3986 KiB

Open AccessArticle

Ultra-Wideband Vertical Transition in Coplanar Stripline for Ultra-High-Speed Digital Interfaces

by Mun-Ju Kim, Jung-Seok Lee, Byung-Cheol Min, Jeong-Sik Choi, Sachin Kumar, Hyun-Chul Choi and Kang-Wook Kim

Sensors 2024, 24(10), 3233; https://doi.org/10.3390/s24103233 - 19 May 2024

Viewed by 1266

Abstract

A design method for an ultra-wideband coplanar-stripline-based vertical transition that can be used for ultra-high-speed digital interfaces is proposed. A conventional via structure, based on a differential line (DL), inherently possesses performance limitations (<10 GHz) due to difficulties in maintaining constant line impedance [...] Read more.

A design method for an ultra-wideband coplanar-stripline-based vertical transition that can be used for ultra-high-speed digital interfaces is proposed. A conventional via structure, based on a differential line (DL), inherently possesses performance limitations (<10 GHz) due to difficulties in maintaining constant line impedance and smooth electric field transformation, in addition to the effects of signal skews, FR4 fiber weave, and unbalanced EM interferences. DL-based digital interfaces may not meet the demands of ultra-high-speed digital data transmission required for the upcoming 6G communications. The use of a coplanar stripline (CPS), a type of planar balanced line (BL), for the vertical transition, along with the ultra-wideband DL-to-CPS transition, mostly removes the inherent and unfavorable issues of the DL and enables ultra-high-speed digital data transmission. The design process of the transition is simplified using the analytical design formulas, derived using the conformal mapping method, of the transition. The characteristic line impedances of the transition are calculated and found to be in close agreement with the results obtained from EM simulations. Utilizing these results, the CPS-based vertical transition, maintaining the characteristic line impedance of 100 Ω, is designed and fabricated. The measured results confirm its ultra-wideband characteristics, with a maximum of 1.6 dB insertion loss and more than 10 dB return loss in the frequency range of DC to 30 GHz. Therefore, the proposed CPS-based vertical transition offers a significantly wider frequency bandwidth, i.e., more than three times that of conventional DL-based via structures. Full article

(This article belongs to the Special Issue Microwave/MM-Wave Components for Communications and Sensors)

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24 pages, 10129 KiB

Open AccessArticle

Amphibious Multifunctional Hydrogel Flexible Haptic Sensor with Self-Compensation Mechanism

by Zhenhao Sun, Yunjiang Yin, Baoguo Liu, Tao Xue and Qiang Zou

Sensors 2024, 24(10), 3232; https://doi.org/10.3390/s24103232 - 19 May 2024

Viewed by 1158

Abstract

In recent years, hydrogel-based wearable flexible electronic devices have attracted much attention. However, hydrogel-based sensors are affected by structural fatigue, material aging, and water absorption and swelling, making stability and accuracy a major challenge. In this study, we present a DN-SPEZ dual-network hydrogel [...] Read more.

In recent years, hydrogel-based wearable flexible electronic devices have attracted much attention. However, hydrogel-based sensors are affected by structural fatigue, material aging, and water absorption and swelling, making stability and accuracy a major challenge. In this study, we present a DN-SPEZ dual-network hydrogel prepared using polyvinyl alcohol (PVA), sodium alginate (SA), ethylene glycol (EG), and ZnSO₄ and propose a self-calibration compensation strategy. The strategy utilizes a metal salt solution to adjust the carrier concentration of the hydrogel to mitigate the resistance drift phenomenon to improve the stability and accuracy of hydrogel sensors in amphibious scenarios, such as land and water. The ExpGrow model was used to characterize the trend of the ∆R/R₀ dynamic response curves of the hydrogels in the stress tests, and the average deviation of the fitted curves

\bar{ϵ}

was calculated to quantify the stability differences of different groups. The results showed that the stability of the uncompensated group was much lower than that of the compensated group utilizing LiCl, NaCl, KCl, MgCl₂, and AlCl₃ solutions (

\bar{ϵ}

in the uncompensated group in air was 276.158, 1.888, 2.971, 30.586, and 13.561 times higher than that of the compensated group in LiCl, NaCl, KCl, MgCl₂, and AlCl₃, respectively;

\bar{ϵ}

in the uncompensated group in seawater was 10.287 times, 1.008 times, 1.161 times, 4.986 times, 1.281 times, respectively, higher than that of the compensated group in LiCl, NaCl, KCl, MgCl₂ and AlCl₃). In addition, for the ranking of the compensation effect of different compensation solutions, the concentration of the compensation solution and the ionic radius and charge of the cation were found to be important factors in determining the compensation effect. Detection of events in amphibious environments such as swallowing, robotic arm grasping, Morse code, and finger–wrist bending was also performed in this study. This work provides a viable method for stability and accuracy enhancement of dual-network hydrogel sensors with strain and pressure sensing capabilities and offers solutions for sensor applications in both airborne and underwater amphibious environments. Full article

(This article belongs to the Special Issue Current Research and Future Development for Wearable Measurement Sensors)

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15 pages, 5914 KiB

Open AccessCommunication

Shear Wave Velocity Determination of a Complex Field Site Using Improved Nondestructive SASW Testing

by Gunwoong Kim and Sungmoon Hwang

Sensors 2024, 24(10), 3231; https://doi.org/10.3390/s24103231 - 19 May 2024

Cited by 1 | Viewed by 1065

Abstract

The nondestructive spectral analysis of surface waves (SASW) technique determines the shear wave velocities along the wide wavelength range using Rayleigh-type surface waves that propagate along pairs of receivers on the surface. The typical configuration of source-receivers consists of a vertical source and [...] Read more.

The nondestructive spectral analysis of surface waves (SASW) technique determines the shear wave velocities along the wide wavelength range using Rayleigh-type surface waves that propagate along pairs of receivers on the surface. The typical configuration of source-receivers consists of a vertical source and three vertical receivers arranged in a linear array. While this approach allows for effective site characterization, laterally variable sites are often challenging to characterize. In addition, in a traditional SASW test configuration system, where sources are placed in one direction, the data are collected more on one side, which can cause an imbalance in the interpretation of the data. Data interpretation issues can be resolved by moving the source to opposite ends of the original array and relocating receivers to perform a second complete set of tests. Consequently, two different Vs profiles can be provided with only a small amount of additional time at sites where lateral variability exists. Furthermore, the testing procedure can be modified to enhance the site characterization during data collection. The advantages of performing SASW testing in both directions are discussed using a real case study. Full article

(This article belongs to the Special Issue Advanced Sensors in Nondestructive Testing and Structural Health Monitoring)

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18 pages, 3436 KiB

Open AccessArticle

Polycations as Aptamer-Binding Modulators for Sensitive Fluorescence Anisotropy Assay of Aflatoxin B1

by Alexey V. Samokhvalov, Alena A. Mironova, Sergei A. Eremin, Anatoly V. Zherdev and Boris B. Dzantiev

Sensors 2024, 24(10), 3230; https://doi.org/10.3390/s24103230 - 19 May 2024

Cited by 1 | Viewed by 1146

Abstract

Fluorescence induced by the excitation of a fluorophore with plane-polarized light has a different polarization depending on the size of the fluorophore-containing reagent and the rate of its rotation. Based on this effect, many analytical systems have been implemented in which an analyte [...] Read more.

Fluorescence induced by the excitation of a fluorophore with plane-polarized light has a different polarization depending on the size of the fluorophore-containing reagent and the rate of its rotation. Based on this effect, many analytical systems have been implemented in which an analyte contained in a sample and labeled with a fluorophore (usually fluorescein) competes to bind to antibodies. Replacing antibodies in such assays with aptamers, low-cost and stable oligonucleotide receptors, is complicated because binding a fluorophore to them causes a less significant change in the polarization of emissions. This work proposes and characterizes the compounds of the reaction medium that improve analyte binding and reduce the mobility of the aptamer–fluorophore complex, providing a higher analytical signal and a lower detection limit. This study was conducted on aflatoxin B1 (AFB1), a ubiquitous toxicant contaminating foods of plant origins. Eight aptamers specific to AFB1 with the same binding site and different regions stabilizing their structures were compared for affinity, based on which the aptamer with 38 nucleotides in length was selected. The polymers that interact reversibly with oligonucleotides, such as poly-L-lysine and polyethylene glycol, were tested. It was found that they provide the desired reduction in the depolarization of emitted light as well as high concentrations of magnesium cations. In the selected optimal medium, AFB1 detection reached a limit of 1 ng/mL, which was 12 times lower than in the tris buffer commonly used for anti-AFB1 aptamers. The assay time was 30 min. This method is suitable for controlling almond samples according to the maximum permissible levels of their contamination by AFB1. The proposed approach could be applied to improve other aptamer-based analytical systems. Full article

(This article belongs to the Special Issue Fluorescence Sensors for Biological and Medical Applications)

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The influence of rotational motion on the anisotropy of fluorescence that is emitted after excitation by plane-polarized light. A1, A2—cases of rapid rotation, B1, B2—cases of slow rotation. Additional comments are given in the text. Full article ">Figure 2
Flow chart of the proposed polycation-mediated fluorescence anisotropy assay. (I). Preparation of aptamer solution and AFB1-fluorophore conjugate solution. (II). Addition of samples without or with AFB1 to microplate wells. (III). Addition of the solutions prepared at the step 1 to the wells. (IV). Incubation of the reaction mixture ((A)—the case with AFB1 in the sample, (B)—the case without AFB1 in the sample). (V). Registration of FA in the reaction mixture ((A)—the case with AFB1 in the sample, (B)—the case without AFB1 in the sample). Full article ">Figure 3
(A) The dependencies of fluorescence (A), the change in fluorescence anisotropy (B), and the percentage of bound fraction (C) of AFB1-EDF on the concentration of (orange) initial aptamer; (black) aptamer 22 nt; (dash, red) aptamer 26 nt; (blue) aptamer 32 nt; (magenda) aptamer 38 nt; (dash, olive) aptamer 42 nt; (dash, purple) aptamer 46 nt; (dash, violet) aptamer 54 nt (n = 3). Full article ">Figure 4
The fluorescence anisotropy of AFB1-EDF in the absence and presence of 100 nM of aptamer 38 nt and the ΔFA in: (A) – 20 mM Tris-Acetate, 100 mM NaAcetate, ph 8.4, with different MgAcetate2 concentrations and TB with different PLL (B) and PEG (C) concentrations (n = 3). Full article ">Figure 5
The FA (A) and the ∆FA (B) of AFB1-EDF in the absence and in the presence of 100 nM of the aptamer 38 nt in TB, contain different % (v/v) of organic solvents (n = 3). Full article ">Figure 6
The fluorescence anisotropy of AFB1-EDF in the absence and presence of 100 nM of the aptamer 38 nt and ∆FA in TB and buffers based on 20 mM Tris-acetate, 100 NaAcetate, pH 8.4 with addition of #1—1 M MgAcetate2, 0.4 μM PLL; #2—1 M MgAcetate2, 70 μM PEG; #3—1 M MgAcetate2, 70 μM PEG, 0.4 μM PLL; #4—0.3 M MgAcetate2, 0.4 μM PLL; #5—0.3 M MgAcetate2, 70 μM PEG; #6—0.3 M MgAcetate2, 70 μM PEG, 0.4 μM PLL (n = 3). Full article ">Figure 7
The fluorescence anisotropy (A) and fluorescence anisotropy changes (B) in AFB1-EDF under complexation with the aptamer 38 nt in TB and buffers: #2; #2T—same with 0.1% Tween20; #6; and #6T—same with 0.1% Tween20 (n = 3). Full article ">Figure 8
The dependencies of the fluorescence anisotropy (A) and percentage of bound (B) AFB1-EDF on the concentration of AFB1 in buffer (1) TB and (2) buffer #6T (n = 3). Full article ">

23 pages, 24886 KiB

Open AccessArticle

Corrosion Monitoring by Plastic Optic Fiber Sensor Using Bi-Directional Light Transmission

by Liang Hou and Shinichi Akutagawa

Sensors 2024, 24(10), 3229; https://doi.org/10.3390/s24103229 - 19 May 2024

Cited by 1 | Viewed by 851

Abstract

In this paper, a new sensor is proposed to efficiently gather crucial information on corrosion phenomena and their progression within steel components. Fabricated with plastic optical fibers (POF), the sensor can detect corrosion-induced physical changes in the appearance of monitoring points within the [...] Read more.

In this paper, a new sensor is proposed to efficiently gather crucial information on corrosion phenomena and their progression within steel components. Fabricated with plastic optical fibers (POF), the sensor can detect corrosion-induced physical changes in the appearance of monitoring points within the steel material. Additionally, the new sensor incorporates an innovative structure that efficiently utilizes bi-directional optical transmission in the POF, simplifying the installation procedure and reducing the total cost of the POF cables by as much as 50% when monitoring multiple points. Furthermore, an extremely compact dummy sensor with the length of 5 mm and a diameter of 2.2 mm for corrosion-depth detection was introduced, and its functionality was validated through experiments. This paper outlines the concept and fundamental structure of the proposed sensor; analyzes the results of various experiments; and discusses its effectiveness, prospects, and economic advantages. Full article

(This article belongs to the Special Issue Specialty Optical Fiber-Based Sensors)

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