Sensors

10 pages, 1749 KiB

Open AccessArticle

The Effect of Caffeine on Movement-Related Cortical Potential Morphology and Detection

by Mads Jochumsen, Emma Rahbek Lavesen, Anne Bruun Griem, Caroline Falkenberg-Andersen and Sofie Kirstine Gedsø Jensen

Sensors 2024, 24(12), 4030; https://doi.org/10.3390/s24124030 - 20 Jun 2024

Viewed by 882

Abstract

Movement-related cortical potential (MRCP) is observed in EEG recordings prior to a voluntary movement. It has been used for e.g., quantifying motor learning and for brain-computer interfacing (BCIs). The MRCP amplitude is affected by various factors, but the effect of caffeine is underexplored. [...] Read more.

Movement-related cortical potential (MRCP) is observed in EEG recordings prior to a voluntary movement. It has been used for e.g., quantifying motor learning and for brain-computer interfacing (BCIs). The MRCP amplitude is affected by various factors, but the effect of caffeine is underexplored. The aim of this study was to investigate if a cup of coffee with 85 mg caffeine modulated the MRCP amplitude and the classification of MRCPs versus idle activity, which estimates BCI performance. Twenty-six healthy participants performed 2 × 100 ankle dorsiflexion separated by a 10-min break before a cup of coffee was consumed, followed by another 100 movements. EEG was recorded during the movements and divided into epochs, which were averaged to extract three average MRCPs that were compared. Also, idle activity epochs were extracted. Features were extracted from the epochs and classified using random forest analysis. The MRCP amplitude did not change after consuming caffeine. There was a slight increase of two percentage points in the classification accuracy after consuming caffeine. In conclusion, a cup of coffee with 85 mg caffeine does not affect the MRCP amplitude, and improves MRCP-based BCI performance slightly. The findings suggest that drinking coffee is only a minor confounder in MRCP-related studies. Full article

(This article belongs to the Special Issue Advances in Brain–Computer Interfaces and Sensors)

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15 pages, 6042 KiB

Open AccessArticle

A Ground-Based Electrostatically Suspended Accelerometer

by Hanxiao Liu, Xiaoxia He, Chenhui Wu and Rong Zhang

Sensors 2024, 24(12), 4029; https://doi.org/10.3390/s24124029 - 20 Jun 2024

Viewed by 632

Abstract

In this study, we have developed an electrostatically suspended accelerometer (ESA) specifically designed for ground use. To ensure sufficient overload capacity and minimize noise resulting from high suspension voltage, we introduced a proof mass design featuring a hollow, thin-walled cylinder with a thin [...] Read more.

In this study, we have developed an electrostatically suspended accelerometer (ESA) specifically designed for ground use. To ensure sufficient overload capacity and minimize noise resulting from high suspension voltage, we introduced a proof mass design featuring a hollow, thin-walled cylinder with a thin flange fixed at the center, offering the highest surface-area-to-mass ratio compared to various typical proof mass structures. Preload voltage is directly applied to the proof mass via a golden wire, effectively reducing the maximum supply voltage for suspension. The arrangement of suspension electrodes, offering five degrees of freedom and minimizing cross-talk, was designed to prioritize simplicity and maximize the utilization of electrode area for suspension purposes. The displacement detection and electrostatic suspension force were accurately modeled based on the structure. A controller incorporating an inverse winding mechanism was developed and simulated using Simulink. The simulation results unequivocally demonstrate the successful completion of the stable initial levitation process and suspension under

\pm 1 g

overload. Full article

(This article belongs to the Special Issue Advanced Inertial Sensors: Advances, Challenges and Applications)

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15 pages, 5391 KiB

Open AccessArticle

Determinants of Maximum Magnetic Anomaly Detection Distance

by Hangcheng Li, Jiaming Luo, Jiajun Zhang, Jing Li, Yi Zhang, Wenwei Zhang and Mingji Zhang

Sensors 2024, 24(12), 4028; https://doi.org/10.3390/s24124028 - 20 Jun 2024

Viewed by 805

Abstract

The maximum detection distance is usually the primary concern of magnetic anomaly detection (MAD). Intuition tells us that larger object size, stronger magnetization and finer measurement resolution guarantee a further detectable distance. However, the quantitative relationship between detection distance and the above determinants [...] Read more.

The maximum detection distance is usually the primary concern of magnetic anomaly detection (MAD). Intuition tells us that larger object size, stronger magnetization and finer measurement resolution guarantee a further detectable distance. However, the quantitative relationship between detection distance and the above determinants is seldom studied. In this work, unmanned aerial vehicle-based MAD field experiments are conducted on cargo vessels and NdFeB magnets as typical magnetic objects to give a set of visualized magnetic field flux density images. Isometric finite element models are established, calibrated and analyzed according to the experiment configuration. A maximum detectable distance map as a function of target size and measurement resolution is then obtained from parametric sweeping on an experimentally calibrated finite element analysis model. We find that the logarithm of detectable distance is positively proportional to the logarithm of object size while negatively proportional to the logarithm of resolution, within the ranges of 1 m~500 m and 1 pT~1 μT, respectively. A three-parameter empirical formula (namely distance-size-resolution logarithmic relationship) is firstly developed to determine the most economic sensor configuration for a given detection task, to estimate the maximum detection distance for a given magnetic sensor and object, or to evaluate minimum detectable object size at a given magnetic anomaly detection scenario. Full article

(This article belongs to the Special Issue Advances in Magnetic Anomaly Sensing Systems)

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22 pages, 7497 KiB

Open AccessArticle

Experimental and Numerical Investigation of Bogie Hunting Instability for Railway Vehicles Based on Multiple Sensors

by Biao Zheng, Lai Wei, Jing Zeng and Dafu Zhang

Sensors 2024, 24(12), 4027; https://doi.org/10.3390/s24124027 - 20 Jun 2024

Cited by 3 | Viewed by 1008

Abstract

Bogie hunting instability is one of the common faults in railway vehicles. It not only affects ride comfort but also threatens operational safety. Due to the lower operating speed of metro vehicles, their bogie hunting stability is often overlooked. However, as wheel tread [...] Read more.

Bogie hunting instability is one of the common faults in railway vehicles. It not only affects ride comfort but also threatens operational safety. Due to the lower operating speed of metro vehicles, their bogie hunting stability is often overlooked. However, as wheel tread wear increases, metro vehicles with high conicity wheel–rail contact can also experience bogie hunting instability. In order to enhance the operational safety of metro vehicles, this paper conducts field tests and simulation calculations to study the bogie hunting instability behavior of metro vehicles and proposes corresponding solutions from the perspective of wheel–rail contact relationships. Acceleration and displacement sensors are installed on metro vehicles to collect data, which are processed in real time in 2 s intervals. The lateral acceleration of the frame is analyzed to determine if bogie hunting instability has occurred. Based on calculated safety indicators, it is determined whether deceleration is necessary to ensure the safety of vehicle operation. For metro vehicles in the later stages of wheel wear (after 300,000 km), the stability of their bogies should be monitored in real time. To improve the stability of metro vehicle bogies while ensuring the longevity of wheelsets, metro vehicle wheel treads should be reprofiled regularly, with a recommended reprofiling interval of 350,000 km. Full article

(This article belongs to the Special Issue Sensors for Real-Time Condition Monitoring and Fault Diagnosis)

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19 pages, 11350 KiB

Open AccessArticle

Preparation of CNT/CNF/PDMS/TPU Nanofiber-Based Conductive Films Based on Centrifugal Spinning Method for Strain Sensors

by Shunqi Mei, Bin Xu, Jitao Wan and Jia Chen

Sensors 2024, 24(12), 4026; https://doi.org/10.3390/s24124026 - 20 Jun 2024

Cited by 3 | Viewed by 994

Abstract

Flexible conductive films are a key component of strain sensors, and their performance directly affects the overall quality of the sensor. However, existing flexible conductive films struggle to maintain high conductivity while simultaneously ensuring excellent flexibility, hydrophobicity, and corrosion resistance, thereby limiting their [...] Read more.

Flexible conductive films are a key component of strain sensors, and their performance directly affects the overall quality of the sensor. However, existing flexible conductive films struggle to maintain high conductivity while simultaneously ensuring excellent flexibility, hydrophobicity, and corrosion resistance, thereby limiting their use in harsh environments. In this paper, a novel method is proposed to fabricate flexible conductive films via centrifugal spinning to generate thermoplastic polyurethane (TPU) nanofiber substrates by employing carbon nanotubes (CNTs) and carbon nanofibers (CNFs) as conductive fillers. These fillers are anchored to the nanofibers through ultrasonic dispersion and impregnation techniques and subsequently modified with polydimethylsiloxane (PDMS). This study focuses on the effect of different ratios of CNTs to CNFs on the film properties. Research demonstrated that at a 1:1 ratio of CNTs to CNFs, with TPU at a 20% concentration and PDMS solution at 2 wt%, the conductive films crafted from these blended fillers exhibited outstanding performance, characterized by electrical conductivity (31.4 S/m), elongation at break (217.5%), and tensile cycling stability (800 cycles at 20% strain). Furthermore, the nanofiber-based conductive films were tested by attaching them to various human body parts. The tests demonstrated that these films effectively respond to motion changes at the wrist, elbow joints, and chest cavity, underscoring their potential as core components in strain sensors. Full article

(This article belongs to the Section Nanosensors)

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16 pages, 4237 KiB

Open AccessArticle

An Integrated LSTM-Rule-Based Fusion Method for the Localization of Intelligent Vehicles in a Complex Environment

by Quan Yuan, Fuwu Yan, Zhishuai Yin, Chen Lv, Jie Hu, Yue Li and Jinhai Wang

Sensors 2024, 24(12), 4025; https://doi.org/10.3390/s24124025 - 20 Jun 2024

Viewed by 734

Abstract

To improve the accuracy and robustness of autonomous vehicle localization in a complex environment, this paper proposes a multi-source fusion localization method that integrates GPS, laser SLAM, and an odometer model. Firstly, fuzzy rules are constructed to accurately analyze the in-vehicle localization deviation [...] Read more.

To improve the accuracy and robustness of autonomous vehicle localization in a complex environment, this paper proposes a multi-source fusion localization method that integrates GPS, laser SLAM, and an odometer model. Firstly, fuzzy rules are constructed to accurately analyze the in-vehicle localization deviation and confidence factor to improve the initial fusion localization accuracy. Then, an odometer model for obtaining the projected localization trajectory is constructed. Considering the high accuracy of the odometer’s projected trajectory within a short distance, we used the shape of the projected localization trajectory to inhibit the initial fusion localization noise and used trajectory matching to obtain an accurate localization. Finally, the Dual-LSTM network is constructed to predict the localization and build an electronic fence to guarantee the safety of the vehicle while also guaranteeing the updating of short-distance localization information of the vehicle when the above-mentioned fusion localization is unreliable. Under the limited arithmetic condition of the vehicle platform, accurate and reliable localization is realized in a complex environment. The proposed method was verified by long-time operation on the real vehicle platform, and compared with the EKF fusion localization method, the average root mean square error of localization was reduced by 66%, reaching centimeter-level localization accuracy. Full article

(This article belongs to the Section Intelligent Sensors)

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36 pages, 34495 KiB

Open AccessArticle

A Novel 3D Reconstruction Sensor Using a Diving Lamp and a Camera for Underwater Cave Exploration

by Quentin Massone, Sébastien Druon and Jean Triboulet

Sensors 2024, 24(12), 4024; https://doi.org/10.3390/s24124024 - 20 Jun 2024

Viewed by 797

Abstract

Aquifer karstic structures, due to their complex nature, present significant challenges in accurately mapping their intricate features. Traditional methods often rely on invasive techniques or sophisticated equipment, limiting accessibility and feasibility. In this paper, a new approach is proposed for a non-invasive, low-cost [...] Read more.

Aquifer karstic structures, due to their complex nature, present significant challenges in accurately mapping their intricate features. Traditional methods often rely on invasive techniques or sophisticated equipment, limiting accessibility and feasibility. In this paper, a new approach is proposed for a non-invasive, low-cost 3D reconstruction using a camera that observes the light projection of a simple diving lamp. The method capitalizes on the principles of structured light, leveraging the projection of light contours onto the karstic surfaces. By capturing the resultant light patterns with a camera, three-dimensional representations of the structures are reconstructed. The simplicity and portability of the equipment required make this method highly versatile, enabling deployment in diverse underwater environments. This approach is validated through extensive field experiments conducted in various aquifer karstic settings. The results demonstrate the efficacy of this method in accurately delineating intricate karstic features with remarkable detail and resolution. Furthermore, the non-destructive nature of this technique minimizes disturbance to delicate aquatic ecosystems while providing valuable insights into the subterranean landscape. This innovative methodology not only offers a cost-effective and non-invasive means of mapping aquifer karstic structures but also opens avenues for comprehensive environmental monitoring and resource management. Its potential applications span hydrogeological studies, environmental conservation efforts, and sustainable water resource management practices in karstic terrains worldwide. Full article

(This article belongs to the Special Issue Sensors for Path Planning and Navigation in Robotics and Autonomous Vehicles)

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16 pages, 7468 KiB

Open AccessArticle

A Low-Cost Sensing Solution for SHM, Exploiting a Dedicated Approach for Signal Recognition

by Bruno Andò, Danilo Greco, Giacomo Navarra and Francesco Lo Iacono

Sensors 2024, 24(12), 4023; https://doi.org/10.3390/s24124023 - 20 Jun 2024

Viewed by 661

Abstract

Health assessment and preventive maintenance of structures are mandatory to predict injuries and to schedule required interventions, especially in seismic areas. Structural health monitoring aims to provide a robust and effective approach to obtaining valuable information on structural conditions of buildings and civil [...] Read more.

Health assessment and preventive maintenance of structures are mandatory to predict injuries and to schedule required interventions, especially in seismic areas. Structural health monitoring aims to provide a robust and effective approach to obtaining valuable information on structural conditions of buildings and civil infrastructures, in conjunction with methodologies for the identification and, sometimes, localization of potential risks. In this paper a low-cost solution for structural health monitoring is proposed, exploiting a customized embedded system for the acquisition and storing of measurement signals. Experimental surveys for the assessment of the sensing node have also been performed. The obtained results confirmed the expected performances, especially in terms of resolution in acceleration and tilt measurement, which are 0.55 mg and 0.020°, respectively. Moreover, we used a dedicated algorithm for the classification of recorded signals in the following three classes: noise floor (being mainly related to intrinsic noise of the sensing system), exogenous sources (not correlated to the dynamic behavior of the structure), and structural responses (the response of the structure to external stimuli, such as seismic events, artificially forced and/or environmental solicitations). The latter is of main interest for the investigation of structures’ health, while other signals need to be recognized and filtered out. The algorithm, which has been tested against real data, demonstrates relevant features in performing the above-mentioned classification task. Full article

(This article belongs to the Special Issue Eurosensors 2023 Selected Papers)

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18 pages, 19175 KiB

Open AccessArticle

Ethereum Phishing Scam Detection Based on Data Augmentation Method and Hybrid Graph Neural Network Model

by Zhen Chen, Sheng-Zheng Liu, Jia Huang, Yu-Han Xiu, Hao Zhang and Hai-Xia Long

Sensors 2024, 24(12), 4022; https://doi.org/10.3390/s24124022 - 20 Jun 2024

Viewed by 1213

Abstract

The rapid advancement of blockchain technology has fueled the prosperity of the cryptocurrency market. Unfortunately, it has also facilitated certain criminal activities, particularly the increasing issue of phishing scams on blockchain platforms such as Ethereum. Consequently, developing an efficient phishing detection system is [...] Read more.

The rapid advancement of blockchain technology has fueled the prosperity of the cryptocurrency market. Unfortunately, it has also facilitated certain criminal activities, particularly the increasing issue of phishing scams on blockchain platforms such as Ethereum. Consequently, developing an efficient phishing detection system is critical for ensuring the security and reliability of cryptocurrency transactions. However, existing methods have shortcomings in dealing with sample imbalance and effective feature extraction. To address these issues, this study proposes an Ethereum phishing scam detection method based on DA-HGNN (Data Augmentation Method and Hybrid Graph Neural Network Model), validated by real Ethereum datasets to prove its effectiveness. Initially, basic node features consisting of 11 attributes were designed. This study applied a sliding window sampling method based on node transactions for data augmentation. Since phishing nodes often initiate numerous transactions, the augmented samples tended to balance. Subsequently, the Temporal Features Extraction Module employed Conv1D (One-Dimensional Convolutional neural network) and GRU-MHA (GRU-Multi-Head Attention) models to uncover intrinsic relationships between features from the time sequences and to mine adequate local features, culminating in the extraction of temporal features. The GAE (Graph Autoencoder) concept was then leveraged, with SAGEConv (Graph SAGE Convolution) as the encoder. In the SAGEConv reconstruction module, by reconstructing the relationships between transaction graph nodes, the structural features of the nodes were learned, obtaining reconstructed node embedding representations. Ultimately, phishing fraud nodes were further identified by integrating temporal features, basic features, and embedding representations. A real Ethereum dataset was collected for evaluation, and the DA-HGNN model achieved an AUC-ROC (Area Under the Receiver Operating Characteristic Curve) of 0.994, a Recall of 0.995, and an F1-score of 0.994, outperforming existing methods and baseline models. Full article

(This article belongs to the Section Internet of Things)

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12 pages, 3250 KiB

Open AccessArticle

Self-Powered Acceleration Sensor for Distance Prediction via Triboelectrification

by Zhengbing Ding, Dinh Cong Nguyen, Hakjeong Kim, Xing Wang, Kyungwho Choi, Jihae Lee and Dukhyun Choi

Sensors 2024, 24(12), 4021; https://doi.org/10.3390/s24124021 - 20 Jun 2024

Cited by 1 | Viewed by 806

Abstract

Accurately predicting the distance an object will travel to its destination is very important in various sports. Acceleration sensors as a means of real-time monitoring are gaining increasing attention in sports. Due to the low energy output and power density of Triboelectric Nanogenerators [...] Read more.

Accurately predicting the distance an object will travel to its destination is very important in various sports. Acceleration sensors as a means of real-time monitoring are gaining increasing attention in sports. Due to the low energy output and power density of Triboelectric Nanogenerators (TENGs), recent efforts have focused on developing various acceleration sensors. However, these sensors suffer from significant drawbacks, including large size, high complexity, high power input requirements, and high cost. Here, we described a portable and cost-effective real-time refreshable strategy design comprising a series of individually addressable and controllable units based on TENGs embedded in a flexible substrate. This results in a highly sensitive, low-cost, and self-powered acceleration sensor. Putting, which accounts for nearly half of all strokes played, is obviously an important component of the golf game. The developed acceleration sensor has an accuracy controlled within 5%. The initial velocity and acceleration of the forward movement of a rolling golf ball after it is hit by a putter can be displayed, and the stopping distance is quickly calculated and predicted in about 7 s. This research demonstrates the application of the portable TENG-based acceleration sensor while paving the way for designing portable, cost-effective, scalable, and harmless ubiquitous self-powered acceleration sensors. Full article

(This article belongs to the Special Issue Advances in Nanosensors and Nanogenerators - 2nd Edition)

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Figure 1
Structural design and working principle of the acceleration sensors. (a) Structural diagram of the acceleration sensor. (b) When an object moves horizontally above the sensor, electrostatic induction occurs between the object and the three sensors, charge transfer takes place between the object and the sensor material, and the corresponding voltage signal is shown on the oscilloscope. (c) Simulation of the potential difference between the object and the sensor material during the contact electrification phase using COMSOL Multiphysics 5.6. Full article ">Figure 2
Measurements and performance analysis of the acceleration sensors. (a) Calculation of the acceleration and distance based on the voltage signals generated by TENGs. (b) The object passing over sensors of different widths <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>w</mi> </mrow> <mrow> <mi>e</mi> </mrow> </msub> </mrow> </semantics></math> and space <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>w</mi> </mrow> <mrow> <mi>g</mi> </mrow> </msub> </mrow> </semantics></math>. (c) Errors between the theoretical distance and the actual measured distance for different sensors at various speeds. (d) The maximum voltage generated by the object when passing over different sensors. Full article ">Figure 3
Experimental platform and response characteristics. (a) Schematic of the ball motion test under different initial kinetic energies. (b) The object acquires different initial kinetic energies by falling through different angles. (c–e) Graphs of the Voltage−Time relationship of the object rolling forward across the mat after gaining kinetic energy from the hammer falling from angles of 30, 60, and 90°, respectively, as shown in each inset. Full article ">Figure 4
Comparison of different performances of the TENG-based acceleration sensors. (a) Algorithmic block diagram of acceleration sensors. (b,c) The acceleration and speed display, respectively, of the object passing through different types of sensors under different initial kinetic energies. (d–f) The predicted distance and actual distance that the object can roll under different initial kinetic energies and the error involved, respectively. Full article ">Figure 5
Practical application of the acceleration sensor based on TENG in golf sports. (a) Schematic of an athlete hitting a golf ball. (b) Schematic showing that the data read by the acceleration sensor can be automatically transmitted to mobile phones and smartwatches. (c–e) The golf ball passes through the TENG sensor to obtain its actual acceleration, speed, and distance on mobile phones and smartwatches. Scale bar: 20 cm. (f,i) The fabricated 1 m sensor-containing mat of 60 mm width × 400 mm spacing. Scale bar: 10 cm. (ii,iii) The sensor in (i) can predict a ball rolling to about 5 m and 8 m, respectively. (iv) A sensor with a width of 30 mm and a spacing of 600 mm can predict the ball rolling to a distance of about 10 m. Full article ">

16 pages, 2062 KiB

Open AccessCommunication

Enhancing Hospital Efficiency and Patient Care: Real-Time Tracking and Data-Driven Dispatch in Patient Transport

by Su-Wen Huang, Shyue-Yow Chiou, Rung-Ching Chen and Chayanon Sub-r-pa

Sensors 2024, 24(12), 4020; https://doi.org/10.3390/s24124020 - 20 Jun 2024

Viewed by 1062

Abstract

Inefficient patient transport in hospitals often leads to delays, overworked staff, and suboptimal resource utilization, ultimately impacting patient care. Existing dispatch management algorithms are often evaluated in simulation environments, raising concerns about their real-world applicability. This study presents a real-world experiment that bridges [...] Read more.

Inefficient patient transport in hospitals often leads to delays, overworked staff, and suboptimal resource utilization, ultimately impacting patient care. Existing dispatch management algorithms are often evaluated in simulation environments, raising concerns about their real-world applicability. This study presents a real-world experiment that bridges the gap between theoretical dispatch algorithms and real-world implementation. It applies process capability analysis at Taichung Veterans General Hospital in Taichung, Taiwan, and utilizes IoT for real-time tracking of staff and medical devices to address challenges associated with manual dispatch processes. Experimental data collected from the hospital underwent statistical evaluation between January 2021 and December 2021. The results of our experiment, which compared the use of traditional dispatch methods with the Beacon dispatch method, found that traditional dispatch had an overtime delay of 41.0%; in comparison, the Beacon dispatch method had an overtime delay of 26.5%. These findings demonstrate the transformative potential of this solution for not only hospital operations but also for improving service quality across the healthcare industry in the context of smart hospitals. Full article

(This article belongs to the Special Issue IoT-Based Smart Environments, Applications and Tools)

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27 pages, 14228 KiB

Open AccessArticle

High-Magnification Object Tracking with Ultra-Fast View Adjustment and Continuous Autofocus Based on Dynamic-Range Focal Sweep

by Tianyi Zhang, Kohei Shimasaki, Idaku Ishii and Akio Namiki

Sensors 2024, 24(12), 4019; https://doi.org/10.3390/s24124019 - 20 Jun 2024

Viewed by 854

Abstract

Active vision systems (AVSs) have been widely used to obtain high-resolution images of objects of interest. However, tracking small objects in high-magnification scenes is challenging due to shallow depth of field (DoF) and narrow field of view (FoV). To address this, we introduce [...] Read more.

Active vision systems (AVSs) have been widely used to obtain high-resolution images of objects of interest. However, tracking small objects in high-magnification scenes is challenging due to shallow depth of field (DoF) and narrow field of view (FoV). To address this, we introduce a novel high-speed AVS with a continuous autofocus (C-AF) approach based on dynamic-range focal sweep and a high-frame-rate (HFR) frame-by-frame tracking pipeline. Our AVS leverages an ultra-fast pan-tilt mechanism based on a Galvano mirror, enabling high-frequency view direction adjustment. Specifically, the proposed C-AF approach uses a 500 fps high-speed camera and a focus-tunable liquid lens operating at a sine wave, providing a 50 Hz focal sweep around the object’s optimal focus. During each focal sweep, 10 images with varying focuses are captured, and the one with the highest focus value is selected, resulting in a stable output of well-focused images at 50 fps. Simultaneously, the object’s depth is measured using the depth-from-focus (DFF) technique, allowing dynamic adjustment of the focal sweep range. Importantly, because the remaining images are only slightly less focused, all 500 fps images can be utilized for object tracking. The proposed tracking pipeline combines deep-learning-based object detection, K-means color clustering, and HFR tracking based on color filtering, achieving 500 fps frame-by-frame tracking. Experimental results demonstrate the effectiveness of the proposed C-AF approach and the advanced capabilities of the high-speed AVS for magnified object tracking. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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19 pages, 5434 KiB

Open AccessArticle

A Method of Precise Auto-Calibration in a Micro-Electro-Mechanical System Accelerometer

by Sergiusz Łuczak, Magdalena Ekwińska and Daniel Tomaszewski

Sensors 2024, 24(12), 4018; https://doi.org/10.3390/s24124018 - 20 Jun 2024

Viewed by 778

Abstract

A novel design of a MEMS (Micro-Electromechanical System) capacitive accelerometer fabricated by surface micromachining, with a structure enabling precise auto-calibration during operation, is presented. Precise auto-calibration was introduced to ensure more accurate acceleration measurements compared to standard designs. The standard mechanical structure of [...] Read more.

A novel design of a MEMS (Micro-Electromechanical System) capacitive accelerometer fabricated by surface micromachining, with a structure enabling precise auto-calibration during operation, is presented. Precise auto-calibration was introduced to ensure more accurate acceleration measurements compared to standard designs. The standard mechanical structure of the accelerometer (seismic mass integrated with elastic suspension and movable plates coupled with fixed plates forming a system of differential sensing capacitors) was equipped with three movable detection electrodes coupled with three fixed electrodes, thus creating three atypical tunneling displacement transducers detecting three specific positions of seismic mass with high precision, enabling the auto-calibration of the accelerometer while it was being operated. Auto-calibration is carried out by recording the accelerometer indication while the seismic mass occupies a specific position, which corresponds to a known value of acting acceleration determined in a pre-calibration process. The diagram and the design of the mechanical structure of the accelerometer, the block diagram of the electronic circuits, and the mathematical relationships used for auto-calibration are presented. The results of the simulation studies related to mechanical and electric phenomena are discussed. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2024)

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15 pages, 5832 KiB

Open AccessArticle

Detection of Multi-Layered Bond Delamination Defects Based on Full Waveform Inversion

by Jiawei Wen, Can Jiang and Hao Chen

Sensors 2024, 24(12), 4017; https://doi.org/10.3390/s24124017 - 20 Jun 2024

Viewed by 751

Abstract

This study aimed to address the challenges encountered in traditional bulk wave delamination detection methods characterized by low detection efficiency. Additionally, the limitations of guided wave delamination detection methods were addressed, particularly those utilizing reflected waves, which are susceptible to edge reflections, thus [...] Read more.

This study aimed to address the challenges encountered in traditional bulk wave delamination detection methods characterized by low detection efficiency. Additionally, the limitations of guided wave delamination detection methods were addressed, particularly those utilizing reflected waves, which are susceptible to edge reflections, thus complicating effective defect extraction. Leveraging the full waveform inversion algorithm, an innovative approach was established for detecting delamination defects in multi-layered structures using ultrasonic guided wave arrays. First, finite element modeling was employed to simulate guided wave data acquisition by a circular array within an aluminum–epoxy bilayer structure with embedded delamination defects. Subsequently, the full waveform inversion algorithm was applied to reconstruct both regular and irregular delamination defects. Analysis results indicated the efficacy of the proposed approach in accurately identifying delamination defects of varying shapes. Furthermore, an experimental platform for guided wave delamination defect detection was established, and experiments were conducted on a steel–cement bilayer structure containing an irregular delamination defect. The experimental results validated the exceptional imaging precision of our proposed technique for identifying delamination defects in multi-layered boards. In summary, the proposed method can accurately determine both the positions and sizes of defects with higher detection efficiency than traditional pulse-echo delamination detection methods. Full article

(This article belongs to the Topic Advances in Non-Destructive Testing Methods, 2nd Volume)

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29 pages, 815 KiB

Open AccessReview

Literature Review of Deep-Learning-Based Detection of Violence in Video

by Pablo Negre, Ricardo S. Alonso, Alfonso González-Briones, Javier Prieto and Sara Rodríguez-González

Sensors 2024, 24(12), 4016; https://doi.org/10.3390/s24124016 - 20 Jun 2024

Cited by 1 | Viewed by 2597

Abstract

Physical aggression is a serious and widespread problem in society, affecting people worldwide. It impacts nearly every aspect of life. While some studies explore the root causes of violent behavior, others focus on urban planning in high-crime areas. Real-time violence detection, powered by [...] Read more.

Physical aggression is a serious and widespread problem in society, affecting people worldwide. It impacts nearly every aspect of life. While some studies explore the root causes of violent behavior, others focus on urban planning in high-crime areas. Real-time violence detection, powered by artificial intelligence, offers a direct and efficient solution, reducing the need for extensive human supervision and saving lives. This paper is a continuation of a systematic mapping study and its objective is to provide a comprehensive and up-to-date review of AI-based video violence detection, specifically in physical assaults. Regarding violence detection, the following have been grouped and categorized from the review of the selected papers: 21 challenges that remain to be solved, 28 datasets that have been created in recent years, 21 keyframe extraction methods, 16 types of algorithm inputs, as well as a wide variety of algorithm combinations and their corresponding accuracy results. Given the lack of recent reviews dealing with the detection of violence in video, this study is considered necessary and relevant. Full article

(This article belongs to the Special Issue Edge Computing in IoT Networks Based on Artificial Intelligence)

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18 pages, 1120 KiB

Open AccessArticle

An Enhanced FGI-GSRx Software-Defined Receiver for the Execution of Long Datasets

by Muwahida Liaquat, Mohammad Zahidul H. Bhuiyan, Saiful Islam, Into Pääkkönen and Sanna Kaasalainen

Sensors 2024, 24(12), 4015; https://doi.org/10.3390/s24124015 - 20 Jun 2024

Viewed by 874

Abstract

The Global Navigation Satellite System (GNSS) software-defined receivers offer greater flexibility, cost-effectiveness, customization, and integration capabilities compared to traditional hardware-based receivers, making them essential for a wide range of applications. The continuous evolution of GNSS research and the availability of new features require [...] Read more.

The Global Navigation Satellite System (GNSS) software-defined receivers offer greater flexibility, cost-effectiveness, customization, and integration capabilities compared to traditional hardware-based receivers, making them essential for a wide range of applications. The continuous evolution of GNSS research and the availability of new features require these software-defined receivers to upgrade continuously to facilitate the latest requirements. The Finnish Geospatial Research Institute (FGI) has been supporting the GNSS research community with its open-source implementations, such as a MATLAB-based GNSS software-defined receiver `FGI-GSRx’ and a Python-based implementation `FGI-OSNMA’ for utilizing Galileo’s Open Service Navigation Message Authentication (OSNMA). In this context, longer datasets are crucial for GNSS software-defined receivers to support adaptation, optimization, and facilitate testing to investigate and develop future-proof receiver capabilities. In this paper, we present an updated version of FGI-GSRx, namely, FGI-GSRx-v2.0.0, which is also available as an open-source resource for the research community. FGI-GSRx-v2.0.0 offers improved performance as compared to its previous version, especially for the execution of long datasets. This is carried out by optimizing the receiver’s functionality and offering a newly added parallel processing feature to ensure faster capabilities to process the raw GNSS data. This paper also presents an analysis of some key design aspects of previous and current versions of FGI-GSRx for a better insight into the receiver’s functionalities. The results show that FGI-GSRx-v2.0.0 offers about a 40% run time execution improvement over FGI-GSRx-v1.0.0 in the case of the sequential processing mode and about a 59% improvement in the case of the parallel processing mode, with 17 GNSS satellites from GPS and Galileo. In addition, an attempt is made to execute v2.0.0 with MATLAB’s own parallel computing toolbox. A detailed performance comparison reveals an improvement of about 43% in execution time over the v2.0.0 parallel processing mode for the same GNSS scenario. Full article

(This article belongs to the Special Issue GNSS Software-Defined Radio Receivers: Status and Perspectives)

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12 pages, 1243 KiB

Open AccessArticle

A Microvascular Segmentation Network Based on Pyramidal Attention Mechanism

by Hong Zhang, Wei Fang and Jiayun Li

Sensors 2024, 24(12), 4014; https://doi.org/10.3390/s24124014 - 20 Jun 2024

Cited by 1 | Viewed by 718

Abstract

The precise segmentation of retinal vasculature is crucial for the early screening of various eye diseases, such as diabetic retinopathy and hypertensive retinopathy. Given the complex and variable overall structure of retinal vessels and their delicate, minute local features, the accurate extraction of [...] Read more.

The precise segmentation of retinal vasculature is crucial for the early screening of various eye diseases, such as diabetic retinopathy and hypertensive retinopathy. Given the complex and variable overall structure of retinal vessels and their delicate, minute local features, the accurate extraction of fine vessels and edge pixels remains a technical challenge in the current research. To enhance the ability to extract thin vessels, this paper incorporates a pyramid channel attention module into a U-shaped network. This allows for more effective capture of information at different levels and increased attention to vessel-related channels, thereby improving model performance. Simultaneously, to prevent overfitting, this paper optimizes the standard convolutional block in the U-Net with the pre-activated residual discard convolution block, thus improving the model’s generalization ability. The model is evaluated on three benchmark retinal datasets: DRIVE, CHASE_DB1, and STARE. Experimental results demonstrate that, compared to the baseline model, the proposed model achieves improvements in sensitivity (Sen) scores of 7.12%, 9.65%, and 5.36% on these three datasets, respectively, proving its strong ability to extract fine vessels. Full article

(This article belongs to the Section Biomedical Sensors)

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57 pages, 2562 KiB

Open AccessReview

A Review of Predictive Analytics Models in the Oil and Gas Industries

by Putri Azmira R Azmi, Marina Yusoff and Mohamad Taufik Mohd Sallehud-din

Sensors 2024, 24(12), 4013; https://doi.org/10.3390/s24124013 - 20 Jun 2024

Cited by 2 | Viewed by 3194

Abstract

Enhancing the management and monitoring of oil and gas processes demands the development of precise predictive analytic techniques. Over the past two years, oil and its prediction have advanced significantly using conventional and modern machine learning techniques. Several review articles detail the developments [...] Read more.

Enhancing the management and monitoring of oil and gas processes demands the development of precise predictive analytic techniques. Over the past two years, oil and its prediction have advanced significantly using conventional and modern machine learning techniques. Several review articles detail the developments in predictive maintenance and the technical and non-technical aspects of influencing the uptake of big data. The absence of references for machine learning techniques impacts the effective optimization of predictive analytics in the oil and gas sectors. This review paper offers readers thorough information on the latest machine learning methods utilized in this industry’s predictive analytical modeling. This review covers different forms of machine learning techniques used in predictive analytical modeling from 2021 to 2023 (91 articles). It provides an overview of the details of the papers that were reviewed, describing the model’s categories, the data’s temporality, field, and name, the dataset’s type, predictive analytics (classification, clustering, or prediction), the models’ input and output parameters, the performance metrics, the optimal model, and the model’s benefits and drawbacks. In addition, suggestions for future research directions to provide insights into the potential applications of the associated knowledge. This review can serve as a guide to enhance the effectiveness of predictive analytics models in the oil and gas industries. Full article

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

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18 pages, 23457 KiB

Open AccessArticle

An Improved YOLOv8 Network for Detecting Electric Pylons Based on Optical Satellite Image

by Xin Chi, Yu Sun, Yingjun Zhao, Donghua Lu, Yan Gao and Yiting Zhang

Sensors 2024, 24(12), 4012; https://doi.org/10.3390/s24124012 - 20 Jun 2024

Viewed by 1162

Abstract

Electric pylons are crucial components of power infrastructure, requiring accurate detection and identification for effective monitoring of transmission lines. This paper proposes an innovative model, the EP-YOLOv8 network, which incorporates new modules: the DSLSK-SPPF and EMS-Head. The DSLSK-SPPF module is designed to capture [...] Read more.

Electric pylons are crucial components of power infrastructure, requiring accurate detection and identification for effective monitoring of transmission lines. This paper proposes an innovative model, the EP-YOLOv8 network, which incorporates new modules: the DSLSK-SPPF and EMS-Head. The DSLSK-SPPF module is designed to capture the surrounding features of electric pylons more effectively, enhancing the model’s adaptability to the complex shapes of these structures. The EMS-Head module enhances the model’s ability to capture fine details of electric pylons while maintaining a lightweight design. The EP-YOLOv8 network optimizes traditional YOLOv8n parameters, demonstrating a significant improvement in electric pylon detection accuracy with an average [email protected] value of 95.5%. The effective detection of electric pylons by the EP-YOLOv8 demonstrates its ability to overcome the inefficiencies inherent in existing optical satellite image-based models, particularly those related to the unique characteristics of electric pylons. This improvement will significantly aid in monitoring the operational status and layout of power infrastructure, providing crucial insights for infrastructure management and maintenance. Full article

(This article belongs to the Section Sensing and Imaging)

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19 pages, 2399 KiB

Open AccessArticle

Accurate 3D LiDAR SLAM System Based on Hash Multi-Scale Map and Bidirectional Matching Algorithm

by Tingchen Ma, Lingxin Kong, Yongsheng Ou and Sheng Xu

Sensors 2024, 24(12), 4011; https://doi.org/10.3390/s24124011 - 20 Jun 2024

Viewed by 1063

Abstract

Simultaneous localization and mapping (SLAM) is a hot research area that is widely required in many robotics applications. In SLAM technology, it is essential to explore an accurate and efficient map model to represent the environment and develop the corresponding data association methods [...] Read more.

Simultaneous localization and mapping (SLAM) is a hot research area that is widely required in many robotics applications. In SLAM technology, it is essential to explore an accurate and efficient map model to represent the environment and develop the corresponding data association methods needed to achieve reliable matching from measurements to maps. These two key elements impact the working stability of the SLAM system, especially in complex scenarios. However, previous literature has not fully addressed the problems of efficient mapping and accurate data association. In this article, we propose a novel hash multi-scale (H-MS) map to ensure query efficiency with accurate modeling. In the proposed map, the inserted map point will simultaneously participate in modeling voxels of different scales in a voxel group, enabling the map to represent objects of different scales in the environment effectively. Meanwhile, the root node of the voxel group is saved to a hash table for efficient access. Secondly, considering the one-to-many (1

\times 10^{3}

order of magnitude) high computational data association problem caused by maintaining multi-scale voxel landmarks simultaneously in the H-MS map, we further propose a bidirectional matching algorithm (MSBM). This algorithm utilizes forward–reverse–forward projection to balance the efficiency and accuracy problem. The proposed H-MS map and MSBM algorithm are integrated into a completed LiDAR SLAM (HMS-SLAM) system. Finally, we validated the proposed map model, matching algorithm, and integrated system on the public KITTI dataset. The experimental results show that, compared with the ikd tree map, the H-MS map model has higher insertion and deletion efficiency, both having

O (1)

time complexity. The computational efficiency and accuracy of the MSBM algorithm are better than that of the small-scale priority matching algorithm, and the computing speed of the MSBM achieves 49 ms/time under a single CPU thread. In addition, the HMS-SLAM system built in this article has also reached excellent performance in terms of mapping accuracy and memory usage. Full article

(This article belongs to the Special Issue Sensors and Algorithms for 3D Visual Analysis and SLAM)

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12 pages, 2757 KiB

Open AccessArticle

Multi-Parameter Characterization of Liquid-to-Ice Phase Transition Using Bulk Acoustic Waves

by Andrey Smirnov, Vladimir Anisimkin, Natalia Voronova, Vadim Kashin and Iren Kuznetsova

Sensors 2024, 24(12), 4010; https://doi.org/10.3390/s24124010 - 20 Jun 2024

Viewed by 699

Abstract

The detection of the liquid-to-ice transition is an important challenge for many applications. In this paper, a method for multi-parameter characterization of the liquid-to-ice phase transition is proposed and tested. The method is based on the fundamental properties of bulk acoustic waves (BAWs). [...] Read more.

The detection of the liquid-to-ice transition is an important challenge for many applications. In this paper, a method for multi-parameter characterization of the liquid-to-ice phase transition is proposed and tested. The method is based on the fundamental properties of bulk acoustic waves (BAWs). BAWs with shear vertical (SV) or shear horizontal (SH) polarization cannot propagate in liquids, only in solids such as ice. BAWs with longitudinal (L) polarization, however, can propagate in both liquids and solids, but with different velocities and attenuations. Velocities and attenuations for L-BAWs and SV-BAWs are measured in ice using parameters such as time delay and wave amplitude at a frequency range of 1–37 MHz. Based on these measurements, relevant parameters for Rayleigh surface acoustic waves and Poisson’s modulus for ice are determined. The homogeneity of the ice sample is also detected along its length. A dual sensor has been developed and tested to analyze two-phase transitions in two liquids simultaneously. Distilled water and a 0.9% solution of NaCl in water were used as examples. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2024)

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Figure 1
(a) Schematic view and (b) photo of the BAW sensor for liquid–ice phase transition with input transducer (1), output transducer (2), and cell (3). Full article ">Figure 2
(a) Schematic view and (b) photo of the LBAW sensor for detecting ice homogeneity: input LBAW transducers (1), output LBAW transducers (2), and cell for ice sample at h = 30 mm, h1 = 4 mm, h2 = 4 mm, fL = 13 MHz, l = 17.8 mm, and d = 3.1 mm. Full article ">Figure 3
(a) Schematic view and (b) photo of the dual BAW sensor for simultaneous detection of two liquid-to-ice transitions: input LBAW transducer (1), bar quartz substrate (lz = ly = 32 mm, lx = 16 mm) (2), two cameras of Teflon cells for liquid 1 and liquid 2 or for ice (3, 4), two output LBAW transducers (5, 6) at d = 1 mm, l = 7 mm, h = 15 mm. Full article ">Figure 4
The dependences of the insertion loss S12 vs. time delay τ measured with LBAW in distilled water (a) before (T = +15 °C) and (b) after (T = −15 °C) phase transition. fL = 30 MHz, l = 17.5 mm, d = 2.5 mm. Full article ">Figure 5
The dependences of the insertion loss S12 vs. time delay τ measured for SVBAW in distilled water (a) before (T = +15 °C) and (b) after (T = −15 °C) phase transition at fSV = 25 MHz, l = 3.3 mm, d = 2.7 mm. Full article ">Figure 6
Insertion loss S12 vs. time delay τ measured at top (black line) and bottom (red line) ends of ice sample at T = −20 °C, h = 30 mm, h1 = 4 mm, h2 = 4 mm, fL = 13 MHz, l = 17.8 mm, d = 3.1 mm, and <math display="inline"><semantics> <mrow> <msubsup> <mi>S</mi> <mrow> <msub> <mrow> <mn>12</mn> </mrow> <mi>L</mi> </msub> </mrow> <mrow> <mi>S</mi> <mi>i</mi> <msub> <mi>O</mi> <mn>2</mn> </msub> </mrow> </msubsup> </mrow> </semantics></math> = 37.5 dB (top) and 42.5 dB (bottom). Full article ">Figure 7
Dependence of the insertion loss S12 vs. time delay τ measured in dual BAW sensor for two liquids and two ices simultaneously. The liquids at T = +20 °C (red line) and the ice samples at T = −20 °C (black line). The arrows indicate shifts of the QL and QSV signals due to liquid-to-ice phase transitions at d = 1 mm, l = 7 mm, h = 15 mm, and fL = 13 MHz. Full article ">

19 pages, 7015 KiB

Open AccessArticle

Pipeline Leak Detection: A Comprehensive Deep Learning Model Using CWT Image Analysis and an Optimized DBN-GA-LSSVM Framework

by Muhammad Farooq Siddique, Zahoor Ahmad, Niamat Ullah, Saif Ullah and Jong-Myon Kim

Sensors 2024, 24(12), 4009; https://doi.org/10.3390/s24124009 - 20 Jun 2024

Cited by 8 | Viewed by 2050

Abstract

Detecting pipeline leaks is an essential factor in maintaining the integrity of fluid transport systems. This paper introduces an advanced deep learning framework that uses continuous wavelet transform (CWT) images for precise detection of such leaks. Transforming acoustic signals from pipelines under various [...] Read more.

Detecting pipeline leaks is an essential factor in maintaining the integrity of fluid transport systems. This paper introduces an advanced deep learning framework that uses continuous wavelet transform (CWT) images for precise detection of such leaks. Transforming acoustic signals from pipelines under various conditions into CWT scalograms, followed by signal processing by non-local means and adaptive histogram equalization, results in new enhanced leak-induced scalograms (ELIS) that capture detailed energy fluctuations across time-frequency scales. The fundamental approach takes advantage of a deep belief network (DBN) fine-tuned with a genetic algorithm (GA) and unified with a least squares support vector machine (LSSVM) to improve feature extraction and classification accuracy. The DBN-GA framework precisely extracts informative features, while the LSSVM classifier precisely distinguishes between leaky and non-leak conditions. By concentrating solely on the advanced capabilities of ELIS processed through an optimized DBN-GA-LSSVM model, this research achieves high detection accuracy and reliability, making a significant contribution to pipeline monitoring and maintenance. This innovative approach to capturing complex signal patterns can be applied to real-time leak detection and critical infrastructure safety in several industrial applications. Full article

(This article belongs to the Special Issue Feature Papers in Fault Diagnosis & Sensors 2024)

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19 pages, 630 KiB

Open AccessArticle

Efficiency and Security Evaluation of Lightweight Cryptographic Algorithms for Resource-Constrained IoT Devices

by Indu Radhakrishnan, Shruti Jadon and Prasad B. Honnavalli

Sensors 2024, 24(12), 4008; https://doi.org/10.3390/s24124008 - 20 Jun 2024

Viewed by 2591

Abstract

The IoT has become an integral part of the technological ecosystem that we all depend on. The increase in the number of IoT devices has also brought with it security concerns. Lightweight cryptography (LWC) has evolved to be a promising solution to improve [...] Read more.

The IoT has become an integral part of the technological ecosystem that we all depend on. The increase in the number of IoT devices has also brought with it security concerns. Lightweight cryptography (LWC) has evolved to be a promising solution to improve the privacy and confidentiality aspect of IoT devices. The challenge is to choose the right algorithm from a plethora of choices. This work aims to compare three different LWC algorithms: AES-128, SPECK, and ASCON. The comparison is made by measuring various criteria such as execution time, memory utilization, latency, throughput, and security robustness of the algorithms in IoT boards with constrained computational capabilities and power. These metrics are crucial to determine the suitability and help in making informed decisions on choosing the right cryptographic algorithms to strike a balance between security and performance. Through the evaluation it is observed that SPECK exhibits better performance in resource-constrained IoT devices. Full article

(This article belongs to the Collection Cryptography and Security in IoT and Sensor Networks)

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15 pages, 2752 KiB

Open AccessArticle

A Novel Fast Iterative STAP Method with a Coprime Sampling Structure

by Mingfu Li and Hui Li

Sensors 2024, 24(12), 4007; https://doi.org/10.3390/s24124007 - 20 Jun 2024

Viewed by 661

Abstract

In space-time adaptive processing (STAP), the coprime sampling structure can obtain better clutter suppression capabilities at a lower hardware cost than the uniform linear sampling structure. However, in practical applications, the performance of the algorithm is often limited by the number of training [...] Read more.

In space-time adaptive processing (STAP), the coprime sampling structure can obtain better clutter suppression capabilities at a lower hardware cost than the uniform linear sampling structure. However, in practical applications, the performance of the algorithm is often limited by the number of training samples. To solve this problem, this paper proposes a fast iterative coprime STAP algorithm based on truncated kernel norm minimization (TKNM). This method establishes a virtual clutter covariance matrix (CCM), introduces truncated kernel norm regularization technology to ensure the low rank of the CCM, and transforms the non-convex problem into a convex optimization problem. Finally, a fast iterative solution method based on the alternating direction method is presented. The effectiveness and accuracy of the proposed algorithm are verified through simulation experiments. Full article

(This article belongs to the Section Intelligent Sensors)

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25 pages, 3572 KiB

Open AccessArticle

A Data Compression Method for Wellbore Stability Monitoring Based on Deep Autoencoder

by Shan Song, Xiaoyong Zhao, Zhengbing Zhang and Mingzhang Luo

Sensors 2024, 24(12), 4006; https://doi.org/10.3390/s24124006 - 20 Jun 2024

Viewed by 685

Abstract

The compression method for wellbore trajectory data is crucial for monitoring wellbore stability. However, classical methods like methods based on Huffman coding, compressed sensing, and Differential Pulse Code Modulation (DPCM) suffer from low real-time performance, low compression ratios, and large errors between the [...] Read more.

The compression method for wellbore trajectory data is crucial for monitoring wellbore stability. However, classical methods like methods based on Huffman coding, compressed sensing, and Differential Pulse Code Modulation (DPCM) suffer from low real-time performance, low compression ratios, and large errors between the reconstructed data and the source data. To address these issues, a new compression method is proposed, leveraging a deep autoencoder for the first time to significantly improve the compression ratio. Additionally, the method reduces error by compressing and transmitting residual data from the feature extraction process using quantization coding and Huffman coding. Furthermore, a mean filter based on the optimal standard deviation threshold is applied to further minimize error. Experimental results show that the proposed method achieves an average compression ratio of 4.05 for inclination and azimuth data; compared to the DPCM method, it is improved by 118.54%. Meanwhile, the average mean square error of the proposed method is 76.88, which is decreased by 82.46% when compared to the DPCM method. Ablation studies confirm the effectiveness of the proposed improvements. These findings highlight the efficacy of the proposed method in enhancing wellbore stability monitoring performance. Full article

(This article belongs to the Section Communications)

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18 pages, 13734 KiB

Open AccessArticle

Channel-Blind Joint Source–Channel Coding for Wireless Image Transmission

by Hongjie Yuan, Weizhang Xu, Yuhuan Wang and Xingxing Wang

Sensors 2024, 24(12), 4005; https://doi.org/10.3390/s24124005 - 20 Jun 2024

Viewed by 880

Abstract

Joint source–channel coding (JSCC) based on deep learning has shown significant advancements in image transmission tasks. However, previous channel-adaptive JSCC methods often rely on the signal-to-noise ratio (SNR) of the current channel for encoding, which overlooks the neural network’s self-adaptive capability across varying [...] Read more.

Joint source–channel coding (JSCC) based on deep learning has shown significant advancements in image transmission tasks. However, previous channel-adaptive JSCC methods often rely on the signal-to-noise ratio (SNR) of the current channel for encoding, which overlooks the neural network’s self-adaptive capability across varying SNRs. This paper investigates the self-adaptive capability of deep learning-based JSCC models to dynamically changing channels and introduces a novel method named Channel-Blind JSCC (CBJSCC). CBJSCC leverages the intrinsic learning capability of neural networks to self-adapt to dynamic channels and diverse SNRs without relying on external SNR information. This approach is advantageous, as it is not affected by channel estimation errors and can be applied to one-to-many wireless communication scenarios. To enhance the performance of JSCC tasks, the CBJSCC model employs a specially designed encoder–decoder. Experimental results show that CBJSCC outperforms existing channel-adaptive JSCC methods that depend on SNR estimation and feedback, both in additive white Gaussian noise environments and under slow Rayleigh fading channel conditions. Through a comprehensive analysis of the model’s performance, we further validate the robustness and adaptability of this strategy across different application scenarios, with the experimental results providing strong evidence to support this claim. Full article

(This article belongs to the Special Issue Advances and Applications of Machine Learning for Wireless Communications and Networking)

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15 pages, 8793 KiB

Open AccessArticle

Optical Design of a Hyperspectral Remote-Sensing System Based on an Image-Slicer Integral Field Unit in the Short-Wave Infrared Band

by Yi Ding, Chunyu Liu, Guoxiu Zhang, Pengfei Hao, Shuai Liu, Yingming Zhao, Yuxin Zhang and Hongxin Liu

Sensors 2024, 24(12), 4004; https://doi.org/10.3390/s24124004 - 20 Jun 2024

Viewed by 819

Abstract

Grating-type spectral imaging systems are frequently employed in scenes for high-resolution remote-sensing observations of the Earth. However, the entrance of the grating-type spectral imaging system is a slit or a pinhole. This structure relies on the push broom method, which presents a challenge [...] Read more.

Grating-type spectral imaging systems are frequently employed in scenes for high-resolution remote-sensing observations of the Earth. However, the entrance of the grating-type spectral imaging system is a slit or a pinhole. This structure relies on the push broom method, which presents a challenge in capturing spectral information of transiently changing targets. To address this issue, the IFU is used to slice the focal plane of the telescope system, thereby expanding the instantaneous field of view (IFOV) of the grating-type spectral imaging system. The aberrations introduced by the expansion of the single-slice field of view (FOV) of the IFU are corrected, and the conversion of the IFU’s FOV from arcseconds to degrees is achieved. The design of a spectral imaging system based on an image-slicer IFU for remote sensing is finally completed. The system has a wavelength range of 1400 nm to 2000 nm, and a spectral resolution of better than 3 nm. Compared with the traditional grating-type spectral imaging system, its IFOV is expanded by a factor of four. And it allows for the capture of complete spectral information of transiently changing targets through a single exposure. The simulation results demonstrate that the system has good performance at each sub-slit, thereby validating the effectiveness and advantages of the proposed system for dynamic target capture in remote sensing. Full article

(This article belongs to the Section Remote Sensors)

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12 pages, 1321 KiB

Open AccessArticle

Developing a Five-Minute Normative Database of Heart Rate Variability for Diagnosing Cardiac Autonomic Dysregulation for Patients with Major Depressive Disorder

by Li-Hsin Chang, Min-Han Huang and I-Mei Lin

Sensors 2024, 24(12), 4003; https://doi.org/10.3390/s24124003 - 20 Jun 2024

Viewed by 904

Abstract

Heart rate variability (HRV) is related to cardiac vagal control and emotional regulation and an index for cardiac vagal control and cardiac autonomic activity. This study aimed to develop the Taiwan HRV normative database covering individuals aged 20 to 70 years and to [...] Read more.

Heart rate variability (HRV) is related to cardiac vagal control and emotional regulation and an index for cardiac vagal control and cardiac autonomic activity. This study aimed to develop the Taiwan HRV normative database covering individuals aged 20 to 70 years and to assess its diagnosing validity in patients with major depressive disorder (MDD). A total of 311 healthy participants were in the HRV normative database and divided into five groups in 10-year age groups, and then the means and standard deviations of the HRV indices were calculated. We recruited 272 patients with MDD for cross-validation, compared their HRV indices with the normative database, and then converted them to Z-scores to explore the deviation of HRV in MDD patients from healthy groups. The results found a gradual decline in HRV indices with advancing age in the HC group, and females in the HC group exhibit higher cardiac vagal control and parasympathetic activity than males. Conversely, patients in the MDD group demonstrate lower HRV indices than those in the HC group, with their symptoms of depression and anxiety showing a negative correlation with HRV indices. The Taiwan HRV normative database has good psychometric characteristics of cross-validation. Full article

(This article belongs to the Special Issue Applications of Body Worn Sensors and Wearables)

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19 pages, 11929 KiB

Open AccessArticle

Improved Intrusion Detection Based on Hybrid Deep Learning Models and Federated Learning

by Jia Huang, Zhen Chen, Sheng-Zheng Liu, Hao Zhang and Hai-Xia Long

Sensors 2024, 24(12), 4002; https://doi.org/10.3390/s24124002 - 20 Jun 2024

Viewed by 981

Abstract

The security of the Industrial Internet of Things (IIoT) is of vital importance, and the Network Intrusion Detection System (NIDS) plays an indispensable role in this. Although there is an increasing number of studies on the use of deep learning technology to achieve [...] Read more.

The security of the Industrial Internet of Things (IIoT) is of vital importance, and the Network Intrusion Detection System (NIDS) plays an indispensable role in this. Although there is an increasing number of studies on the use of deep learning technology to achieve network intrusion detection, the limited local data of the device may lead to poor model performance because deep learning requires large-scale datasets for training. Some solutions propose to centralize the local datasets of devices for deep learning training, but this may involve user privacy issues. To address these challenges, this study proposes a novel federated learning (FL)-based approach aimed at improving the accuracy of network intrusion detection while ensuring data privacy protection. This research combines convolutional neural networks with attention mechanisms to develop a new deep learning intrusion detection model specifically designed for the IIoT. Additionally, variational autoencoders are incorporated to enhance data privacy protection. Furthermore, an FL framework enables multiple IIoT clients to jointly train a shared intrusion detection model without sharing their raw data. This strategy significantly improves the model’s detection capability while effectively addressing data privacy and security issues. To validate the effectiveness of the proposed method, a series of experiments were conducted on a real-world Internet of Things (IoT) network intrusion dataset. The experimental results demonstrate that our model and FL approach significantly improve key performance metrics such as detection accuracy, precision, and false-positive rate (FPR) compared to traditional local training methods and existing models. Full article

(This article belongs to the Section Internet of Things)

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26 pages, 2613 KiB

Open AccessSystematic Review

Technologies for Evaluation of Pelvic Floor Functionality: A Systematic Review

by Nikolas Förstl, Ina Adler, Franz Süß and Sebastian Dendorfer

Sensors 2024, 24(12), 4001; https://doi.org/10.3390/s24124001 - 20 Jun 2024

Cited by 1 | Viewed by 1333

Abstract

Pelvic floor dysfunction is a common problem in women and has a negative impact on their quality of life. The aim of this review was to provide a general overview of the current state of technology used to assess pelvic floor functionality. It [...] Read more.

Pelvic floor dysfunction is a common problem in women and has a negative impact on their quality of life. The aim of this review was to provide a general overview of the current state of technology used to assess pelvic floor functionality. It also provides literature research of the physiological and anatomical factors that correlate with pelvic floor health. This systematic review was conducted according to the PRISMA guidelines. The PubMed, ScienceDirect, Cochrane Library, and IEEE databases were searched for publications on sensor technology for the assessment of pelvic floor functionality. Anatomical and physiological parameters were identified through a manual search. In the systematic review, 114 publications were included. Twelve different sensor technologies were identified. Information on the obtained parameters, sensor position, test activities, and subject characteristics was prepared in tabular form from each publication. A total of 16 anatomical and physiological parameters influencing pelvic floor health were identified in 17 published studies and ranked for their statistical significance. Taken together, this review could serve as a basis for the development of novel sensors which could allow for quantifiable prevention and diagnosis, as well as particularized documentation of rehabilitation processes related to pelvic floor dysfunctions. Full article

(This article belongs to the Special Issue Sensing and Signal Processing Technologies for Outpatient Monitoring and Rehabilitation)

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