Sensors

21 pages, 7618 KiB

Open AccessArticle

Statistical Analysis of the Consistency of HRV Analysis Using BCG or Pulse Wave Signals

by Huiying Cui, Zhongyi Wang, Bin Yu, Fangfang Jiang, Ning Geng, Yongchun Li, Lisheng Xu, Dingchang Zheng, Biyong Zhang, Peilin Lu and Stephen E. Greenwald

Sensors 2022, 22(6), 2423; https://doi.org/10.3390/s22062423 - 21 Mar 2022

Cited by 5 | Viewed by 3412

Abstract

Ballistocardiography (BCG) is considered a good alternative to HRV analysis with its non-contact and unobtrusive acquisition characteristics. However, consensus about its validity has not yet been established. In this study, 50 healthy subjects (26.2 ± 5.5 years old, 22 females, 28 males) were [...] Read more.

Ballistocardiography (BCG) is considered a good alternative to HRV analysis with its non-contact and unobtrusive acquisition characteristics. However, consensus about its validity has not yet been established. In this study, 50 healthy subjects (26.2 ± 5.5 years old, 22 females, 28 males) were invited. Comprehensive statistical analysis, including Coefficients of Variation (CV), Lin’s Concordance Correlation Coefficient (LCCC), and Bland-Altman analysis (BA ratio), were utilized to analyze the consistency of BCG and ECG signals in HRV analysis. If the methods gave different answers, the worst case was taken as the result. Measures of consistency such as Mean, SDNN, LF gave good agreement (the absolute value of CV difference < 2%, LCCC > 0.99, BA ratio < 0.1) between J-J (BCG) and R-R intervals (ECG). pNN50 showed moderate agreement (the absolute value of CV difference < 5%, LCCC > 0.95, BA ratio < 0.2), while RMSSD, HF, LF/HF indicated poor agreement (the absolute value of CV difference ≥ 5% or LCCC ≤ 0.95 or BA ratio ≥ 0.2). Additionally, the R-R intervals were compared with P-P intervals extracted from the pulse wave (PW). Except for pNN50, which exhibited poor agreement in this comparison, the performances of the HRV indices estimated from the PW and the BCG signals were similar. Full article

(This article belongs to the Section Biosensors)

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32 pages, 8732 KiB

Open AccessFeature PaperArticle

n-Player Stochastic Duel Game Model with Applied Deep Learning and Its Modern Implications

by Manik Gupta, Bhisham Sharma, Akarsh Tripathi, Shashank Singh, Abhishek Bhola, Rajani Singh and Ashutosh Dhar Dwivedi

Sensors 2022, 22(6), 2422; https://doi.org/10.3390/s22062422 - 21 Mar 2022

Cited by 7 | Viewed by 3526

Abstract

This paper provides a conceptual foundation for stochastic duels and contains a further study of the game models based on the theory of stochastic duels. Some other combat assessment techniques are looked upon briefly; a modern outlook on the applications of the theory [...] Read more.

This paper provides a conceptual foundation for stochastic duels and contains a further study of the game models based on the theory of stochastic duels. Some other combat assessment techniques are looked upon briefly; a modern outlook on the applications of the theory through video games is provided; and the possibility of usage of data generated by popular shooter-type video games is discussed. Impactful works to date are carefully chosen; a timeline of the developments in the theory of stochastic duels is provided; and a brief literature review for the same is conducted, enabling readers to have a broad outlook at the theory of stochastic duels. A new evaluation model is introduced in order to match realistic scenarios. Improvements are suggested and, additionally, a trust mechanism is introduced to identify the intent of a player in order to make the model a better fit for realistic modern problems. The concept of teaming of players is also considered in the proposed mode. A deep-learning model is developed and trained on data generated by video games to support the results of the proposed model. The proposed model is compared to previously published models in a brief comparison study. Contrary to the conventional stochastic duel game combat model, this new proposed model deals with pair-wise duels throughout the game duration. This model is explained in detail, and practical applications of it in the context of the real world are also discussed. The approach toward solving modern-day problems through the use of game theory is presented in this paper, and hence, this paper acts as a foundation for researchers looking forward to an innovation with game theory. Full article

(This article belongs to the Special Issue Fuzzy Systems and Neural Networks for Engineering Applications)

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23 pages, 7105 KiB

Open AccessArticle

Identification Method for Internal Forces of Segmental Tunnel Linings via the Combination of Laser Scanning and Hybrid Structural Analysis

by Yumeng Zhang, Jurij Karlovšek and Xian Liu

Sensors 2022, 22(6), 2421; https://doi.org/10.3390/s22062421 - 21 Mar 2022

Cited by 7 | Viewed by 2346

Abstract

This paper provides a new solution to identify the internal forces of segmental tunnel linings by combining laser scanning and hybrid structural analysis. First, a hybrid structural analysis method for quantifying the internal forces based on displacement monitoring is established, which requires comprehensive [...] Read more.

This paper provides a new solution to identify the internal forces of segmental tunnel linings by combining laser scanning and hybrid structural analysis. First, a hybrid structural analysis method for quantifying the internal forces based on displacement monitoring is established, which requires comprehensive displacement monitoring with high precision and a complete trace history. Motivated by the development of laser scanning, two remedial solutions are proposed for typically insufficient engineering conditions, i.e., lack of displacement developing process and poor accuracy of measurements, which is highlighted in this paper. Therefore, with the help of remedial solutions, the structural analysis is able to be adopted with the application of laser scanning. The tool for developing remedial solutions is the first-order theory of slender circular arches. Virtual tests, based on a calibrated finite element model, were performed to verify the feasibility of the presented hybrid analysis and remedial solutions. In addition, parametric analyses were conducted to study the error propagation from laser scanning to the results of hybrid analysis. The resolution and measurement noise of laser scanning were investigated and discussed. On this basis, advice on combining laser scanning and hybrid structural analysis is proposed. Finally, on-site application of the hybrid analysis on an actual tunnel is presented and discussed. Full article

(This article belongs to the Special Issue Fault Detection and Data Analysis for Structure and Infrastructure Engineering)

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21 pages, 3677 KiB

Open AccessArticle

Underwater Sound Source Localization Based on Passive Time-Reversal Mirror and Ray Theory

by Kuan-Wen Liu, Ching-Jer Huang, Gee-Pinn Too, Zong-You Shen and Yung-Da Sun

Sensors 2022, 22(6), 2420; https://doi.org/10.3390/s22062420 - 21 Mar 2022

Cited by 4 | Viewed by 3565

Abstract

This study investigates the performance of a passive time-reversal mirror (TRM) combined with acoustic ray theory in localizing underwater sound sources with high frequencies (3–7 kHz). The TRM was installed on a floating buoy and comprised four hydrophones. The ray-tracing code BELLHOP was [...] Read more.

This study investigates the performance of a passive time-reversal mirror (TRM) combined with acoustic ray theory in localizing underwater sound sources with high frequencies (3–7 kHz). The TRM was installed on a floating buoy and comprised four hydrophones. The ray-tracing code BELLHOP was used to determine the transfer function between a sound source and a field point. The transfer function in the frequency domain obtained from BELLHOP was transformed into the time domain. The pressure field was then obtained by taking the convolution of the transfer function in the time domain with the time-reversed signals that were received by the hydrophones in the TRM. The location with the maximum pressure value was designated as the location of the source. The performance of the proposed methodology for source localization was tested in a towing tank and in the ocean. The aforementioned tests revealed that even when the distances between a source and the TRM were up to 1600 m, the distance deviations between estimated and actual source locations were mostly less than 2 m. Errors originated mainly from inaccurate depth estimation, and the literature indicates that they can be reduced by increasing the number of TRM elements and their apertures. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 2906 KiB

Open AccessArticle

Motion Shield: An Automatic Notifications System for Vehicular Communications

by Petros Balios, Philotas Kyriakidis, Stelios Zimeras, Petros S. Bithas and Lambros Sarakis

Sensors 2022, 22(6), 2419; https://doi.org/10.3390/s22062419 - 21 Mar 2022

Cited by 1 | Viewed by 2445

Abstract

Motion Shield is an automatic crash notification system that uses a mobile phone to generate automatic alerts related to the safety of a user when the user is boarding a means of transportation. The objective of Motion Shield is to improve road safety [...] Read more.

Motion Shield is an automatic crash notification system that uses a mobile phone to generate automatic alerts related to the safety of a user when the user is boarding a means of transportation. The objective of Motion Shield is to improve road safety by considering a moving vehicle’s risk, estimating the probability of an emergency, and assessing the likelihood of an accident. The system, using multiple sources of external information, the mobile phone sensors’ readings, geolocated information, weather data, and historical evidence of traffic accidents, processes a plethora of parameters in order to predict the onset of an accident and act preventively. All the collected data are forwarded into a decision support system which dynamically calculates the mobility risk and driving behavior aspects in order to proactively send personalized notifications and alerts to the user and a public safety answering point (PSAP) (112). Full article

(This article belongs to the Special Issue Feature Papers in the Internet of Things Section 2022)

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18 pages, 1482 KiB

Open AccessArticle

Microservice Security Framework for IoT by Mimic Defense Mechanism

by Fei Ying, Shengjie Zhao and Hao Deng

Sensors 2022, 22(6), 2418; https://doi.org/10.3390/s22062418 - 21 Mar 2022

Cited by 5 | Viewed by 3154

Abstract

Containers and microservices have become the most popular method for hosting IoT applications in cloud servers. However, one major security issue of this method is that if a container image contains software with security vulnerabilities, the associated microservices also become vulnerable at run-time. [...] Read more.

Containers and microservices have become the most popular method for hosting IoT applications in cloud servers. However, one major security issue of this method is that if a container image contains software with security vulnerabilities, the associated microservices also become vulnerable at run-time. Existing works attempted to reduce this risk with vulnerability-scanning tools. They, however, demand an up-to-date database and may not work with unpublished vulnerabilities. In this paper, we propose a novel system to strengthen container security from unknown attack using the mimic defense framework. Specifically, we constructed a resource pool with variant images and observe the inconsistency in execution results, from which we can identify potential vulnerabilities. To avoid continuous attack, we created a graph-based scheduling strategy to maximize the randomness and heterogeneity of the images used to replace the current images. We implemented a prototype using Kubernetes. Experimental results show that our framework makes hackers have to send

54.9 %

more random requests to complete the attack and increases the defence success rate by around

8.16 %

over the baseline framework to avoid the continuous unknown attacks. Full article

(This article belongs to the Special Issue Smart Sensor Technologies: Transforming Physical Security into the Digital World)

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20 pages, 2913 KiB

Open AccessArticle

Analog-Domain Suppression of Strong Interference Using Hybrid Antenna Array

by Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Diep N. Nguyen, Asanka Kekirigoda and Kin-Ping Hui

Sensors 2022, 22(6), 2417; https://doi.org/10.3390/s22062417 - 21 Mar 2022

Cited by 4 | Viewed by 2355

Abstract

The proliferation of wireless applications, the ever-increasing spectrum crowdedness, as well as cell densification makes the issue of interference increasingly severe in many emerging wireless applications. Most interference management/mitigation methods in the literature are problem-specific and require some cooperation/coordination between different radio frequency [...] Read more.

The proliferation of wireless applications, the ever-increasing spectrum crowdedness, as well as cell densification makes the issue of interference increasingly severe in many emerging wireless applications. Most interference management/mitigation methods in the literature are problem-specific and require some cooperation/coordination between different radio frequency systems. Aiming to seek a more versatile solution to counteracting strong interference, we resort to the hybrid array of analog subarrays and suppress interference in the analog domain so as to greatly reduce the required quantization bits of the analog-to-digital converters and their power consumption. To this end, we design a real-time algorithm to steer nulls towards the interference directions and maintain flat in non-interference directions, solely using constant-modulus phase shifters. To ensure sufficient null depth for interference suppression, we also develop a two-stage method for accurately estimating interference directions. The proposed solution can be applicable to most (if not all) wireless systems as neither training/reference signal nor cooperation/coordination is required. Extensive simulations show that more than 65 dB of suppression can be achieved for 3 spatially resolvable interference signals yet with random directions. Full article

(This article belongs to the Special Issue Communications and Sensing Technologies for the Future)

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48 pages, 3881 KiB

Open AccessReview

Towards Synoptic Water Monitoring Systems: A Review of AI Methods for Automating Water Body Detection and Water Quality Monitoring Using Remote Sensing

by Liping Yang, Joshua Driscol, Sarigai Sarigai, Qiusheng Wu, Christopher D. Lippitt and Melinda Morgan

Sensors 2022, 22(6), 2416; https://doi.org/10.3390/s22062416 - 21 Mar 2022

Cited by 32 | Viewed by 8558

Abstract

Water features (e.g., water quantity and water quality) are one of the most important environmental factors essential to improving climate-change resilience. Remote sensing (RS) technologies empowered by artificial intelligence (AI) have become one of the most demanded strategies to automating water information extraction [...] Read more.

Water features (e.g., water quantity and water quality) are one of the most important environmental factors essential to improving climate-change resilience. Remote sensing (RS) technologies empowered by artificial intelligence (AI) have become one of the most demanded strategies to automating water information extraction and thus intelligent monitoring. In this article, we provide a systematic review of the literature that incorporates artificial intelligence and computer vision methods in the water resources sector with a focus on intelligent water body extraction and water quality detection and monitoring through remote sensing. Based on this review, the main challenges of leveraging AI and RS for intelligent water information extraction are discussed, and research priorities are identified. An interactive web application designed to allow readers to intuitively and dynamically review the relevant literature was also developed. Full article

(This article belongs to the Special Issue Advances in the Monitoring, Diagnosis, and Optimisation of Water Systems)

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Figure 1
Geospatial distribution and simple statistics of the reviewed papers. Note that a freely accessible interactive version of the charts can be accessed via our web app tool (the web app tool URL and its brief demo video are provided in <a href="#app1-sensors-22-02416" class="html-app">Appendix A</a>). We can easily see that the major countries are China and the United States and that the number of published papers by year (2011 to 2021) has dramatically increased since 2018 and 2019. (a) Spatial distribution of reviewed papers based on the first author’s institution location. (b) Topic distribution (water body, water quality, both). (c) Country distribution. (d) Number of published papers by year from 2011 to 2021 on the relevant topics. Full article ">Figure 1 Cont.
Geospatial distribution and simple statistics of the reviewed papers. Note that a freely accessible interactive version of the charts can be accessed via our web app tool (the web app tool URL and its brief demo video are provided in <a href="#app1-sensors-22-02416" class="html-app">Appendix A</a>). We can easily see that the major countries are China and the United States and that the number of published papers by year (2011 to 2021) has dramatically increased since 2018 and 2019. (a) Spatial distribution of reviewed papers based on the first author’s institution location. (b) Topic distribution (water body, water quality, both). (c) Country distribution. (d) Number of published papers by year from 2011 to 2021 on the relevant topics. Full article ">Figure 2
Word cloud visualization of all the reviewed papers (top), water body papers (bottom left), and water quality papers (bottom right). Note that the word clouds are generated from paper titles, abstracts, and keywords. The word clouds provide an informative (general and specific) focus of each set of the papers. For example, both water body and water quality papers share the focus on RS, DL, and neural networks (NN). We can also see that water body extraction tasks tend to focus on the use of convolutional neural networks (CNN), whereas for water quality modeling the use of long short-term memory (LSTM) networks is more prevalent. We can also see that there are specific, unique keywords for water quality, such as “turbidity”, “chl”, and “algal bloom”. Full article ">Figure A1
Our highly interactive web app (accessible publicly at: <a href="https://geoair-lab.github.io/WaterFeatureAI-WebApp/index.html" target="_blank">https://geoair-lab.github.io/WaterFeatureAI-WebApp/index.html</a>, accessed on 5 December 2021) provides the track of scholars and publications with just a few clicks. See an example on the pop-up. Our readers can access (1) a direct link to the PDF file of the paper (note that if there is no free, publicly available version of the paper, we link directly to the journal page of the paper so our readers can obtain the paper if their institution purchases the journal database), (2) the scholar profile (Google Scholar/ResearchGate URL) of the first author, and (3) “Cited by” Google Scholar page. (a) Water body and quality AI literature map pop-up. (b) “Cited by” Google Scholar page corresponding to the paper shown in (a). Full article ">Figure A1 Cont.
Our highly interactive web app (accessible publicly at: <a href="https://geoair-lab.github.io/WaterFeatureAI-WebApp/index.html" target="_blank">https://geoair-lab.github.io/WaterFeatureAI-WebApp/index.html</a>, accessed on 5 December 2021) provides the track of scholars and publications with just a few clicks. See an example on the pop-up. Our readers can access (1) a direct link to the PDF file of the paper (note that if there is no free, publicly available version of the paper, we link directly to the journal page of the paper so our readers can obtain the paper if their institution purchases the journal database), (2) the scholar profile (Google Scholar/ResearchGate URL) of the first author, and (3) “Cited by” Google Scholar page. (a) Water body and quality AI literature map pop-up. (b) “Cited by” Google Scholar page corresponding to the paper shown in (a). Full article ">Figure A2
Example confusion matrix. The classified data indicate the ML/DL model predicted results and the reference data refer to the actual manually annotated data (image source: [<a href="#B161-sensors-22-02416" class="html-bibr">161</a>]). Full article ">

14 pages, 5647 KiB

Open AccessArticle

One4all—A New SCADA Approach

by Bogdan Vaduva, Ionut-Flaviu Pop and Honoriu Valean

Sensors 2022, 22(6), 2415; https://doi.org/10.3390/s22062415 - 21 Mar 2022

Cited by 2 | Viewed by 2781

Abstract

The main purpose of this paper is to introduce a new concept, named “one4all” in the realm of SCADA (Supervisory Control and Data Acquisition) systems, used by a regional company (particularly a water supplying company) for managing the different views of its users. [...] Read more.

The main purpose of this paper is to introduce a new concept, named “one4all” in the realm of SCADA (Supervisory Control and Data Acquisition) systems, used by a regional company (particularly a water supplying company) for managing the different views of its users. As a secondary purpose, the paper presents an integration of such an SCADA system with a GIS (Geographical Information System) system. All the regional water supply companies in Romania manage water and wastewater networks, many sensors and actuators, dozens of water pump plants, several water treatment and wastewater plants, tanks and many hydrophores in different parts of their operating range. Due to the wide geographical operating range, an SCADA system needs to be put in place, but the management of such a system in a traditional way is hard to implement, especially when the human resource is low. The methodology presented in this paper, involving adding helper tables and dynamic template windows within an SCADA tool (“one4all” tool), will show how efficiently the human resource can be used. Additionally, the paper shows that companies as described above, can use a single SCADA system that generates different views for all the managed sub regions instead of different systems for every sub region. Implementing only one SCADA system built with the concept “one4all” in mind, and integrating it with a GIS system that is built on the same principle, represents a new approach that will bring value to any organization willing to adopt it. The concept of “one4all”, implemented as a software tool for an SCADA system, is a new concept that will help any developer to easily build applications that generate different views for different users based on their permissions and their operating range. Finally, the paper presents some examples of the same concept, implemented in a different vertical (GIS) and programming language, thus presenting that a “one4all” concept is viable and helpful, bringing value to the information technology industry. Full article

(This article belongs to the Section Remote Sensors)

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32 pages, 7223 KiB

Open AccessArticle

Sensing System for Plegic or Paretic Hands Self-Training Motivation

by Igor Zubrycki, Ewa Prączko-Pawlak and Ilona Dominik

Sensors 2022, 22(6), 2414; https://doi.org/10.3390/s22062414 - 21 Mar 2022

Viewed by 2591

Abstract

Patients after stroke with paretic or plegic hands require frequent exercises to promote neuroplasticity and to improve hand joint mobilization. Available devices for hand exercising are intended for persons with some level of hand control or provide continuous passive motion with limited patient [...] Read more.

Patients after stroke with paretic or plegic hands require frequent exercises to promote neuroplasticity and to improve hand joint mobilization. Available devices for hand exercising are intended for persons with some level of hand control or provide continuous passive motion with limited patient involvement. Patients can benefit from self-exercising where they use the other hand to exercise the plegic or paretic one. However, post-stroke neuropsychological complications, apathy, and cognitive impairments such as forgetfulness make regular self-exercising difficult. This paper describes Przypominajka v2—a system intended to support self-exercising, remind about it, and motivate patients. We propose a glove-based device with an on-device machine-learning-based exercise scoring, a tablet-based interface, and a web-based application for therapists. The feasibility of on-device inference and the accuracy of correct exercise classification was evaluated on four healthy participants. Whole system use was described in a case study with a patient with a paretic hand. The anomaly classification has an accuracy of 91.3% and

f_{1}

value of 91.6% but achieves poorer results for new users (78% and 81%). The case study showed that patients had a positive reaction to exercising with Przypominajka, but there were issues relating to sensor glove: ease of putting on and clarity of instructions. The paper presents a new way in which sensor systems can support the rehabilitation of after-stroke patients with an on-device machine-learning-based classification that can accurately score and contribute to patient motivation. Full article

(This article belongs to the Special Issue Smart Sensing Systems: Algorithms and Applications—Selected Papers from Signal Processing Symposium 2021 (SPSympo-2021))

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14 pages, 13886 KiB

Open AccessArticle

Development of an Integrated Virtual Reality System with Wearable Sensors for Ergonomic Evaluation of Human–Robot Cooperative Workplaces

by Teodorico Caporaso, Stanislao Grazioso and Giuseppe Di Gironimo

Sensors 2022, 22(6), 2413; https://doi.org/10.3390/s22062413 - 21 Mar 2022

Cited by 15 | Viewed by 3786

Abstract

This work proposes a novel virtual reality system which makes use of wearable sensors for testing and validation of cooperative workplaces from the ergonomic point of view. The main objective is to show, in real time, the ergonomic evaluation based on a muscular [...] Read more.

This work proposes a novel virtual reality system which makes use of wearable sensors for testing and validation of cooperative workplaces from the ergonomic point of view. The main objective is to show, in real time, the ergonomic evaluation based on a muscular activity analysis within the immersive virtual environment. The system comprises the following key elements: a robotic simulator for modeling the robot and the working environment; virtual reality devices for human immersion and interaction within the simulated environment; five surface electromyographic sensors; and one uniaxial accelerometer for measuring the human ergonomic status. The methodology comprises the following steps: firstly, the virtual environment is constructed with an associated immersive tutorial for the worker; secondly, an ergonomic toolbox is developed for muscular analysis. This analysis involves multiple ergonomic outputs: root mean square for each muscle, a global electromyographic score, and a synthetic index. They are all visualized in the immersive environment during the execution of the task. To test this methodology, experimental trials are conducted on a real use case in a human–robot cooperative workplace typical of the automotive industry. The results showed that the methodology can effectively be applied in the analysis of human–robot interaction, to endow the workers with self–awareness with respect to their physical conditions. Full article

(This article belongs to the Special Issue Advances in Design and Integration of Wearable Sensors for Ergonomics)

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17 pages, 4095 KiB

Open AccessArticle

An Unsupervised Tunnel Damage Identification Method Based on Convolutional Variational Auto-Encoder and Wavelet Packet Analysis

by Yonglai Zhang, Xiongyao Xie, Hongqiao Li and Biao Zhou

Sensors 2022, 22(6), 2412; https://doi.org/10.3390/s22062412 - 21 Mar 2022

Cited by 18 | Viewed by 2613

Abstract

Finding a low-cost and highly efficient method for identifying subway tunnel damage can greatly reduce catastrophic accidents. At present, tunnel health monitoring is mainly based on the observation of apparent diseases and vibration monitoring, which is combined with a manual inspection to perceive [...] Read more.

Finding a low-cost and highly efficient method for identifying subway tunnel damage can greatly reduce catastrophic accidents. At present, tunnel health monitoring is mainly based on the observation of apparent diseases and vibration monitoring, which is combined with a manual inspection to perceive the tunnel health status. However, these methods have disadvantages such as high cost, short working time, and low identification efficiency. Thus, in this study, a tunnel damage identification algorithm based on the vibration response of in-service train and WPE-CVAE is proposed, which can automatically identify tunnel damage and give the damage location. The method is an unsupervised novelty detection that requires only sufficient normal data on healthy structure for training. This study introduces the theory and implementation process of this method in detail. Through laboratory model tests, the damage of the void behind the tunnel wall is designed to verify the performance of the algorithm. In the test case, the proposed method achieves the damage identification performance with a 96.25% recall rate, 86.75% hit rate, and 91.5% accuracy. Furthermore, compared with the other unsupervised methods, the method performance and noise immunity are better than others, so it has a certain practical value. Full article

(This article belongs to the Special Issue Recent Advances in Sensing and Data Centric Methods for Structural Health Monitoring and Resilience)

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17 pages, 1232 KiB

Open AccessArticle

Development of a 3D Relative Motion Method for Human–Robot Interaction Assessment

by Felipe Ballen-Moreno, Margarita Bautista, Thomas Provot, Maxime Bourgain, Carlos A. Cifuentes and Marcela Múnera

Sensors 2022, 22(6), 2411; https://doi.org/10.3390/s22062411 - 21 Mar 2022

Cited by 6 | Viewed by 2684

Abstract

Exoskeletons have been assessed by qualitative and quantitative features known as performance indicators. Within these, the ergonomic indicators have been isolated, creating a lack of methodologies to analyze and assess physical interfaces. In this sense, this work presents a three-dimensional relative motion assessment [...] Read more.

Exoskeletons have been assessed by qualitative and quantitative features known as performance indicators. Within these, the ergonomic indicators have been isolated, creating a lack of methodologies to analyze and assess physical interfaces. In this sense, this work presents a three-dimensional relative motion assessment method. This method quantifies the difference of orientation between the user’s limb and the exoskeleton link, providing a deeper understanding of the Human–Robot interaction. To this end, the AGoRA exoskeleton was configured in a resistive mode and assessed using an optoelectronic system. The interaction quantified a difference of orientation considerably at a maximum value of 41.1 degrees along the sagittal plane. It extended the understanding of the Human–Robot Interaction throughout the three principal human planes. Furthermore, the proposed method establishes a performance indicator of the physical interfaces of an exoskeleton. Full article

(This article belongs to the Section Sensors and Robotics)

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The AGoRA exoskeleton. Uni-lateral actuation on the right side. Full article ">Figure 2
Scheme of thigh’s vectors. Reference vectors are used to establish the user’s local frame. The <math display="inline"><semantics> <mover accent="true"> <msub> <mi>t</mi> <mrow> <mi>u</mi> <mi>p</mi> </mrow> </msub> <mo>→</mo> </mover> </semantics></math> vector is defined by the middle point between EPSD and EASD markers. Similarly, the <math display="inline"><semantics> <mover accent="true"> <msub> <mi>t</mi> <mrow> <mi>l</mi> <mi>o</mi> <mi>w</mi> </mrow> </msub> <mo>→</mo> </mover> </semantics></math> is created by the middle point between CLD and CMD markers. Finally, previous vectors are used to define the longitudinal vector of the thigh <math display="inline"><semantics> <mover accent="true"> <mrow> <mi>v</mi> <mi>e</mi> <mi>c</mi> <msub> <mi>t</mi> <mi>y</mi> </msub> </mrow> <mo>→</mo> </mover> </semantics></math>. Full article ">Figure 3
2D-projection of the descriptive scheme of rotation matrices. Full article ">Figure 4
Controller scheme of the assistance mode. The admittance controller’ model is defined as a mass-damper system, including a module of position limitation, velocity saturation, and emergency button. These modules are aimed at the device’s security. (A.C.: Admittance Controller, F.L.: Feedforward Loop, F.M.: Friction Model, M.M.: Modulation Method, G.P.D.: Gait Phase Detection, U.: User, A.S.: Actuation System, V.D.: Velocity Driver, V.S.: Velocity Saturation, P.L.: Position Limitation, M.P.L.: Module of Position Limitation). Full article ">Figure 5
Markers setup used in the pilot study. Highlighted in red are the user’s markers and the exoskeleton’s markers in blue. Full article ">Figure 6
Flowchart of the data processing and implementation. Full article ">Figure 7
The difference of orientation’s outcomes per subject. (a) Subject 1, (b) Subject 2, (c) Subject 3, (d) Subject 4, (e) Subject 5, (f) Subject 6. The red curve refers to the <math display="inline"><semantics> <mrow> <mi>R</mi> <mi>o</mi> <msub> <mi>t</mi> <mi>X</mi> </msub> </mrow> </semantics></math>, the blue curve refers to the <math display="inline"><semantics> <mrow> <mi>R</mi> <mi>o</mi> <msub> <mi>t</mi> <mi>Y</mi> </msub> </mrow> </semantics></math>, and the green curve refers to the <math display="inline"><semantics> <mrow> <mi>R</mi> <mi>o</mi> <msub> <mi>t</mi> <mi>Z</mi> </msub> </mrow> </semantics></math>. In all cases, the dotted signal represents the average of the cycles for each orientation signal per subject; and the shaded curve represents the standard deviation of the cycles for each orientation signal per subject. Full article ">

21 pages, 2422 KiB

Open AccessArticle

EggBlock: Design and Implementation of Solar Energy Generation and Trading Platform in Edge-Based IoT Systems with Blockchain

by Subin Kwak, Joohyung Lee, Jangkyum Kim and Hyeontaek Oh

Sensors 2022, 22(6), 2410; https://doi.org/10.3390/s22062410 - 21 Mar 2022

Cited by 7 | Viewed by 3190

Abstract

In this paper, to balance power supplement from the solar energy’s intermittent and unpredictable generation, we design a solar energy generation and trading platform (EggBlock) using Internet of Things (IoT) systems and blockchain technique. Without a centralized broker, the proposed EggBlock platform can [...] Read more.

In this paper, to balance power supplement from the solar energy’s intermittent and unpredictable generation, we design a solar energy generation and trading platform (EggBlock) using Internet of Things (IoT) systems and blockchain technique. Without a centralized broker, the proposed EggBlock platform can promote energy trading between users equipped with solar panels, and balance demand and generation. By applying the second price sealed-bid auction, which is one of the suitable pricing mechanisms in the blockchain technique, it is possible to derive truthful bidding of market participants according to their utility function and induce the proceed transaction. Furthermore, for efficient generation of solar energy, EggBlock proposes a Q-learning-based dynamic panel control mechanism. Specifically, we set the instantaneous direction of the solar panel and the amount of power generation as the state and reward, respectively. The angle of the panel to be moved becomes an action at the next time step. Then, we continuously update the Q-table using transfer learning, which can cope with recent changes in the surrounding environment or weather. We implement the proposed EggBlock platform using Ethereum’s smart contract for reliable transactions. At the end of the paper, measurement-based experiments show that the proposed EggBlock achieves reliable and transparent energy trading on the blockchain and converges to the optimal direction with short iterations. Finally, the results of the study show that an average energy generation gain of 35% is obtained. Full article

(This article belongs to the Topic IoT for Energy Management Systems and Smart Cities)

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23 pages, 5193 KiB

Open AccessArticle

A Novel Analytical Modeling Approach for Quality Propagation of Transient Analysis of Serial Production Systems

by Shihong Liu, Shichang Du, Lifeng Xi, Yiping Shao and Delin Huang

Sensors 2022, 22(6), 2409; https://doi.org/10.3390/s22062409 - 21 Mar 2022

Cited by 2 | Viewed by 1952

Abstract

Production system modeling (PSM) for quality propagation involves mapping the principles between components and systems. While most existing studies focus on the steady-state analysis, the transient quality analysis remains largely unexplored. It is of significance to fully understand quality propagation, especially during transients, [...] Read more.

Production system modeling (PSM) for quality propagation involves mapping the principles between components and systems. While most existing studies focus on the steady-state analysis, the transient quality analysis remains largely unexplored. It is of significance to fully understand quality propagation, especially during transients, to shorten product changeover time, decrease quality loss, and improve quality. In this paper, a novel analytical PSM approach is established based on the Markov model, to explore product quality propagation for transient analysis of serial multi-stage production systems. The cascade property for quality propagation among correlated sequential stages was investigated, taking into account both the status of the current stage and the quality of the outputs from upstream stages. Closed-form formulae to evaluate transient quality performances of multi-stage systems were formulated, including the dynamics of system quality, settling time, and quality loss. An iterative procedure utilizing the aggregation technique is presented to approximate transient quality performance with computational efficiency and high accuracy. Moreover, system theoretic properties of quality measures were analyzed and the quality bottleneck identification method was investigated. In the case study, the modeling error was 0.36% and the calculation could clearly track system dynamics; quality bottleneck was identified to decrease the quality loss and facilitate continuous improvement. The experimental results illustrate the applicability of the proposed PSM approach. Full article

(This article belongs to the Topic Artificial Intelligence in Smart Industrial Diagnostics and Manufacturing)

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32 pages, 3325 KiB

Open AccessArticle

Heuristic Greedy Scheduling of Electric Vehicles in Vehicle-to-Grid Microgrid Owned Aggregators

by Alaa E. Abdel-Hakim and Farag K. Abo-Elyousr

Sensors 2022, 22(6), 2408; https://doi.org/10.3390/s22062408 - 21 Mar 2022

Cited by 7 | Viewed by 2573

Abstract

In on-grid microgrids, electric vehicles (EVs) have to be efficiently scheduled for cost-effective electricity consumption and network operation. The stochastic nature of the involved parameters along with their large number and correlations make such scheduling a challenging task. This paper aims at identifying [...] Read more.

In on-grid microgrids, electric vehicles (EVs) have to be efficiently scheduled for cost-effective electricity consumption and network operation. The stochastic nature of the involved parameters along with their large number and correlations make such scheduling a challenging task. This paper aims at identifying pertinent innovative solutions for reducing the relevant total costs of the on-grid EVs within hybrid microgrids. To optimally scale the EVs, a heuristic greedy approach is considered. Unlike most existing scheduling methodologies in the literature, the proposed greedy scheduler is model-free, training-free, and yet efficient. The proposed approach considers different factors such as the electricity price, on-grid EVs state of arrival and departure, and the total revenue to meet the load demands. The greedy-based approach behaves satisfactorily in terms of fulfilling its objective for the hybrid microgrid system, which is established of photovoltaic, wind turbine, and a local utility grid. Meanwhile, the on-grid EVs are being utilized as an energy storage exchange location. A real time hardware-in-the-loop experimentation is comprehensively conducted to maximize the earned profit. Through different uncertainty scenarios, the ability of the proposed greedy approach to obtain a global optimal solution is assessed. A data simulator was developed for the purposes of generating evaluation datasets, which captures uncertainties in the behaviors of the system’s parameters. The greedy-based strategy is considered applicable, scalable, and efficient in terms of total operating expenditures. Furthermore, as EVs penetration became more versatile, total expenses decreased significantly. Using simulated data of an effective operational duration of 500 years, the proposed approach succeeded in cutting down the energy consumption costs by about 50–85%, beating existing state-of-the-arts results. The proposed approach is proved to be tolerant to the large amounts of uncertainties that are involved in the system’s operational data. Full article

(This article belongs to the Section Vehicular Sensing)

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16 pages, 4181 KiB

Open AccessArticle

Performance Degradation Prediction Using LSTM with Optimized Parameters

by Yawei Hu, Ran Wei, Yang Yang, Xuanlin Li, Zhifu Huang, Yongbin Liu, Changbo He and Huitian Lu

Sensors 2022, 22(6), 2407; https://doi.org/10.3390/s22062407 - 21 Mar 2022

Cited by 12 | Viewed by 3204

Abstract

Predicting the degradation of mechanical components, such as rolling bearings is critical to the proper monitoring of the condition of mechanical equipment. A new method, based on a long short-term memory network (LSTM) algorithm, has been developed to improve the accuracy of degradation [...] Read more.

Predicting the degradation of mechanical components, such as rolling bearings is critical to the proper monitoring of the condition of mechanical equipment. A new method, based on a long short-term memory network (LSTM) algorithm, has been developed to improve the accuracy of degradation prediction. The model parameters are optimized via improved particle swarm optimization (IPSO). Regarding how this applies to the rolling bearings, firstly, multi-dimension feature parameters are extracted from the bearing’s vibration signals and fused into responsive features by using the kernel joint approximate diagonalization of eigen-matrices (KJADE) method. Then, the between-class and within-class scatter (SS) are calculated to develop performance degradation indicators. Since network model parameters influence the predictive accuracy of the LSTM model, an IPSO algorithm is used to obtain the optimal prediction model via the LSTM model parameters’ optimization. Finally, the LSTM model, with said optimal parameters, was used to predict the degradation trend of the bearing’s performance. The experiment’s results show that the proposed method can effectively identify the trends of degradation and performance. Moreover, the predictive accuracy of this proposed method is greater than that of the extreme learning machine (ELM) and support vector regression (SVR), which are the algorithms conventionally used in degradation modeling. Full article

(This article belongs to the Special Issue Machine Health Monitoring and Fault Diagnosis Techniques)

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12 pages, 1841 KiB

Open AccessArticle

Method to Minimize the Errors of AI: Quantifying and Exploiting Uncertainty of Deep Learning in Brain Tumor Segmentation

by Joohyun Lee, Dongmyung Shin, Se-Hong Oh and Haejin Kim

Sensors 2022, 22(6), 2406; https://doi.org/10.3390/s22062406 - 21 Mar 2022

Cited by 7 | Viewed by 2760

Abstract

Despite the unprecedented success of deep learning in various fields, it has been recognized that clinical diagnosis requires extra caution when applying recent deep learning techniques because false prediction can result in severe consequences. In this study, we proposed a reliable deep learning [...] Read more.

Despite the unprecedented success of deep learning in various fields, it has been recognized that clinical diagnosis requires extra caution when applying recent deep learning techniques because false prediction can result in severe consequences. In this study, we proposed a reliable deep learning framework that could minimize incorrect segmentation by quantifying and exploiting uncertainty measures. The proposed framework demonstrated the effectiveness of a public dataset: Multimodal Brain Tumor Segmentation Challenge 2018. By using this framework, segmentation performances, particularly for small lesions, were improved. Since the segmentation of small lesions is difficult but also clinically significant, this framework could be effectively applied to the medical imaging field. Full article

(This article belongs to the Special Issue Machine Learning Techniques for Medical Imaging, Sensing, and Analysis)

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Figure 1
Flow diagram of our study. Brain tumor segmentation on MRI was automatically performed, and three types of lesions (enhancing tumor, necrotic/non-enhancing tumor, and edema) were distinguished. The proposed framework can minimize the error of the baseline model. To evaluate the framework, we used a public dataset, BraTS18. T1 = T1-weighted; T1ce = T1 contrast-enhanced; T2 = T2-weighted; FLAIR = Fluid Attenuated Inversion Recovery; HGG = high-grade glioma (glioblastoma); LGG = low-grade glioma. Full article ">Figure 2
Overview of the proposed framework. (a) Feedforward multimodal MRI images into a baseline model with Monte Carlo dropout and generate a baseline segmentation map (Step. 1) (b) Quantify uncertainty values of baseline segmentation map by four different measures (Step. 2). Feedforward both images and uncertainty maps into the proposed model and generate proposed segmentation map (Step. 3); MC dropout = Monte Carlo dropout; 3D CNN = 3-dimensional convolutional neural network; UAM = uncertainty attention module. Full article ">Figure 3
Architecture of uncertainty attention module (UAM). This subnetwork module can effectively exploit uncertainty maps by applying an attention mechanism. This module is plugged into any neural network. This architecture, including the operations, was highly optimized by an ablation study. Conv = convolution; AvgPool = average pooling; MaxPool = max pooling; Favg = feature maps from average pooling operation; Fmax = feature maps from max pooling operation. (a) UAM architecture overview. (b) Specific architecture of green box. Full article ">Figure 4
Uncertainty quantification results: Automated segmentation results by baseline model, corresponding uncertainty maps, image, and manual segmentation by experienced neurologists (ground truth). Each scan is from a different patient. The color code of the segmentation map and uncertainty map is described below. Red in the uncertainty map means an uncertain predictive area, and blue means a certain predictive area. ET = enhancing tumor; NCR/NET = necrotic and non-enhancing tumor; ED = peritumoral edema. (a) Totally correct prediction and UMs. (b) Totally incorrect prediction and UMs. (c) Slightly incorrect prediction and UMs. (d) Moderately incorrect prediction and UMs. Full article ">Figure 5
Uncertainty exploitation results: Automatic segmentation results by baseline/proposed method and manual segmentation by experienced neurologists (ground-truth). The images are subsequent results of <a href="#sensors-22-02406-f004" class="html-fig">Figure 4</a>. The proposed method can exploit uncertainty maps to perform brain tumor segmentation. (a) scans with no tumor. (b) scans with ET and ED. (c) scans with all lesions. (d) scans with all lesions. Full article ">

12 pages, 5107 KiB

Open AccessArticle

Multi-Scale Attention 3D Convolutional Network for Multimodal Gesture Recognition

by Huizhou Chen, Yunan Li, Huijuan Fang, Wentian Xin, Zixiang Lu and Qiguang Miao

Sensors 2022, 22(6), 2405; https://doi.org/10.3390/s22062405 - 21 Mar 2022

Cited by 15 | Viewed by 3116

Abstract

Gesture recognition is an important direction in computer vision research. Information from the hands is crucial in this task. However, current methods consistently achieve attention on hand regions based on estimated keypoints, which will significantly increase both time and complexity, and may lose [...] Read more.

Gesture recognition is an important direction in computer vision research. Information from the hands is crucial in this task. However, current methods consistently achieve attention on hand regions based on estimated keypoints, which will significantly increase both time and complexity, and may lose position information of the hand due to wrong keypoint estimations. Moreover, for dynamic gesture recognition, it is not enough to consider only the attention in the spatial dimension. This paper proposes a multi-scale attention 3D convolutional network for gesture recognition, with a fusion of multimodal data. The proposed network achieves attention mechanisms both locally and globally. The local attention leverages the hand information extracted by the hand detector to focus on the hand region, and reduces the interference of gesture-irrelevant factors. Global attention is achieved in both the human-posture context and the channel context through a dual spatiotemporal attention module. Furthermore, to make full use of the differences between different modalities of data, we designed a multimodal fusion scheme to fuse the features of RGB and depth data. The proposed method is evaluated using the Chalearn LAP Isolated Gesture Dataset and the Briareo Dataset. Experiments on these two datasets prove the effectiveness of our network and show it outperforms many state-of-the-art methods. Full article

(This article belongs to the Special Issue Sensing Systems for Sign Language Recognition)

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Figure 1
Our pipeline of the proposed network. This network takes I3D [<a href="#B4-sensors-22-02405" class="html-bibr">4</a>] as the backbone and consists of three parts: (1) A local attention module to enhance the network’s attention to the hand region. (2) A dual spatiotemporal attention module to extract global spatiotemporal posture context information. (3) A multimodal fusion network for fusing different modality features. Full article ">Figure 2
Sample of different data used in local attention: (a) raw RGB data; (b) hand data processed by hand detector; (c) fusion of raw RGB data and hand data. Full article ">Figure 3
Architecture of SVAM. SVAM is designed for capturing the vision dependence in the spatiotemporal domain. This module takes the feature extracted by I3D as input. Q, K, and V correspond to query, key, and value matrices in the attention mechanism. The output feature is the result of the selective aggregation of features at all positions with the weighted sum of the input features. Full article ">Figure 4
Architecture of SCAM. SCAM takes the feature extracted by I3D as input, which is designed for capturing the dependence between channels in the spatiotemporal domain. <math display="inline"><semantics> <mrow> <msup> <mi>A</mi> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </msup> <mo>,</mo> <msup> <mi>A</mi> <mrow> <mo stretchy="false">(</mo> <mn>2</mn> <mo stretchy="false">)</mo> </mrow> </msup> <mo>,</mo> <msup> <mi>A</mi> <mrow> <mo stretchy="false">(</mo> <mn>3</mn> <mo stretchy="false">)</mo> </mrow> </msup> </mrow> </semantics></math> correspond to query, key, and value matrices in the attention mechanism. The output feature of each channel is the result of the selective aggregation of features on all channels, and the weighted sum of the input features. Full article ">Figure 5
Comparison of channel feature map between DA-3D and MSA-3D: (a) features of each channel extracted after the third layer of DA-3D network; (b) features of each channel extracted after the third layer of MSA-3D network. Full article ">Figure 6
Comparison of channel feature map between I3D and MSA-3D: (a) features of each channel extracted after the third layer of I3D network; (b) features of each channel extracted after the third layer of MSA-3D network. Full article ">

15 pages, 4193 KiB

Open AccessCommunication

Integrated Resource Management for Fog Networks

by Jui-Pin Yang and Hui-Kai Su

Sensors 2022, 22(6), 2404; https://doi.org/10.3390/s22062404 - 21 Mar 2022

Viewed by 1848

Abstract

In this paper, we consider integrated resource management for fog networks inclusive of intelligent energy perception, service level agreement (SLA) planning and replication-based hotspot offload (RHO). In the beginning, we propose an intelligent energy perception scheme which dynamically classifies the fog nodes into [...] Read more.

In this paper, we consider integrated resource management for fog networks inclusive of intelligent energy perception, service level agreement (SLA) planning and replication-based hotspot offload (RHO). In the beginning, we propose an intelligent energy perception scheme which dynamically classifies the fog nodes into a hot set, a warm set or a cold set, based on their load conditions. The fog nodes in the hot set are responsible for a quality of service (QoS) guarantee and the fog nodes in the cold set are maintained at a low-energy state to save energy consumption. Moreover, the fog nodes in the warm set are used to balance the QoS guarantee and energy consumption. Secondly, we propose an SLA mapping scheme which effectively identifies the SLA elements with the same semantics. Finally, we propose a replication-based load-balancing scheme, namely RHO. The RHO can leverage the skewed access pattern caused by the hotspot services. In addition, it greatly reduces communication overheads because the load conditions are updated only when the load variations exceed a specific threshold. Finally, we use computer simulations to compare the performance of the RHO with other schemes under a variety of load conditions. In a word, we propose a comprehensive and feasible solution that contributes to the integrated resource management of fog networks. Full article

(This article belongs to the Section Communications)

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16 pages, 4764 KiB

Open AccessArticle

Distorted Acquisition of Dynamic Events Sensed by Frequency-Scanning Fiber-Optic Interrogators and a Mitigation Strategy

by Hari Datta Bhatta, Roy Davidi, Arie Yeredor and Moshe Tur

Sensors 2022, 22(6), 2403; https://doi.org/10.3390/s22062403 - 21 Mar 2022

Cited by 2 | Viewed by 1977

Abstract

Fiber-optic dynamic interrogators, which use periodic frequency scanning, actually sample a time-varying measurand on a non-uniform time grid. Commonly, however, the sampled values are reported on a uniform time grid, synchronized with the periodic scanning. It is the novel and noteworthy message of [...] Read more.

Fiber-optic dynamic interrogators, which use periodic frequency scanning, actually sample a time-varying measurand on a non-uniform time grid. Commonly, however, the sampled values are reported on a uniform time grid, synchronized with the periodic scanning. It is the novel and noteworthy message of this paper that this artificial assignment may give rise to significant distortions in the recovered signal. These distortions increase with both the signal frequency and measurand dynamic range for a given sampling rate and frequency scanning span of the interrogator. They may reach disturbing values in dynamic interrogators, which trade-off scanning speed with scanning span. The paper also calls for manufacturers of such interrogators to report the sampled values along with their instants of acquisition, allowing interpolation algorithms to substantially reduce the distortion. Experimental verification of a simulative analysis includes: (i) a commercial dynamic interrogator of ‘continuous’ FBG fibers that attributes the measurand values to a uniform time grid; as well as (ii) a dynamic Brillouin Optical time Domain (BOTDA) laboratory setup, which provides the sampled measurand values together with the sampling instants. Here, using the available measurand-dependent sampling instants, we demonstrate a significantly cleaner signal recovery using spline interpolation. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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9 pages, 1394 KiB

Open AccessCommunication

A Study of the Detection of SARS-CoV-2 ORF1ab Gene by the Use of Electrochemiluminescent Biosensor Based on Dual-Probe Hybridization

by Chunying Jiang, Xihui Mu, Shuai Liu, Zhiwei Liu, Bin Du, Jiang Wang and Jianjie Xu

Sensors 2022, 22(6), 2402; https://doi.org/10.3390/s22062402 - 21 Mar 2022

Cited by 11 | Viewed by 2222

Abstract

To satisfy the need to develop highly sensitive methods for detecting the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and further enhance detection efficiency and capability, a new method was created for detecting SARS-CoV-2 of the open reading frames 1ab (ORF1ab) target [...] Read more.

To satisfy the need to develop highly sensitive methods for detecting the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and further enhance detection efficiency and capability, a new method was created for detecting SARS-CoV-2 of the open reading frames 1ab (ORF1ab) target gene by a electrochemiluminescence (ECL) biosensor based on dual-probe hybridization through the use of a detection model of “magnetic capture probes—targeted nucleic acids—Ru(bpy)₃²⁺ labeled signal probes”. The detection model used magnetic particles coupled with a biotin-labeled complementary nucleic acid sequence of the SARS-CoV-2 ORF1ab target gene as the magnetic capture probes and Ru(bpy)₃²⁺ labeled amino modified another complementary nucleic acid sequence as the signal probes, which combined the advantages of the highly specific dual-probe hybridization and highly sensitive ECL biosensor technology. In the range of 0.1 fM~10 µM, the method made possible rapid and sensitive detection of the ORF1ab gene of the SARS-CoV-2 within 30 min, and the limit of detection (LOD) was 0.1 fM. The method can also meet the analytical requirements for simulated samples such as saliva and urine with the definite advantages of a simple operation without nucleic acid amplification, high sensitivity, reasonable reproducibility, and anti-interference solid abilities, expounding a new way for efficient and sensitive detection of SARS-CoV-2. Full article

(This article belongs to the Section Biosensors)

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19 pages, 4771 KiB

Open AccessArticle

Development of a Novel Railway Positioning System Using RFID Technology

by Osama Olaby, Moussa Hamadache, David Soper, Phil Winship and Roger Dixon

Sensors 2022, 22(6), 2401; https://doi.org/10.3390/s22062401 - 21 Mar 2022

Cited by 11 | Viewed by 4657

Abstract

Currently, a number of positioning systems are in use to locate trains on the railway network; but these generally have limited precision. Thus, this paper focuses on testing and validating the suitability of radio frequency identification (RFID) technology, for aligning vehicles to switch [...] Read more.

Currently, a number of positioning systems are in use to locate trains on the railway network; but these generally have limited precision. Thus, this paper focuses on testing and validating the suitability of radio frequency identification (RFID) technology, for aligning vehicles to switch and crossing (S&C) positions on the railway network. This offers the possibility of accurately knowing the position of vehicles equipped with monitoring equipment, such as the network rail track recording vehicle (TRV), and aligning the data with reference to the locations of the S&C (and ideally to key elements within a particular S&C). The concept is to install two tags, one on the switch-toe sleeper and the second on the crossing-nose sleeper, with an RFID reader that will be installed underneath the vehicle. Thus, the key features of the S&C, the switch toe and crossing nose, will be considered as a definitive reference point for the inspection vehicle’s position. As a monitoring vehicle passes over a piece of S&C, the proposed positioning system will provide information about this S&C’s ID, which is stored inside the RFID tags and will indicate the S&C’s GPS coordinates. As part of the research in this paper, more than 400 tests have been performed to investigate two different RFID technologies, passive and semi-passive, tested in a variety of conditions: including different passage speeds, different distances between the RFID reader and the tags, and varied strength signal transmitted between the reader and the tags. Based on lab testing and analysis of the recorded data, it is concluded that passive RFID technology is the most suitable of the two technologies. The conclusions find that the proposed RFID-based solution can offer a more precise positioning solution to be a reference point for the train location within the network. Full article

(This article belongs to the Special Issue Sensing and Monitoring Electric and Electromagnetic Quantities in Railways)

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13 pages, 1238 KiB

Open AccessArticle

An Integrated Millimeter-Wave Satellite Radiometer Working at Room-Temperature with High Photon Conversion Efficiency

by Kerlos Atia Abdalmalak, Gabriel Santamaria Botello, Mallika Irene Suresh, Enderson Falcón-Gómez, Alejandro Rivera Lavado and Luis Enrique García-Muñoz

Sensors 2022, 22(6), 2400; https://doi.org/10.3390/s22062400 - 21 Mar 2022

Cited by 4 | Viewed by 2945

Abstract

In this work, the design of an integrated

183 GHz

radiometer frontend for earth observation applications on satellites is presented. By means of the efficient electro-optic modulation of a laser pump with the observed millimeter-wave signal followed by the detection of the generated [...] Read more.

In this work, the design of an integrated

183 GHz

radiometer frontend for earth observation applications on satellites is presented. By means of the efficient electro-optic modulation of a laser pump with the observed millimeter-wave signal followed by the detection of the generated optical sideband, a room-temperature low-noise receiver frontend alternative to conventional Low Noise Amplifiers (LNAs) or Schottky mixers is proposed. Efficient millimeter-wave to 1550 nm upconversion is realized via a nonlinear optical process in a triply resonant high-Q Lithium Niobate (LN) Whispering Gallery Mode (WGM) resonator. By engineering a micromachined millimeter-wave cavity that maximizes the overlap with the optical modes while guaranteeing phase matching, the system has a predicted normalized photon-conversion efficiency

\approx 10^{- 1}

per

mW

pump power, surpassing the state-of-the-art by around three orders of magnitude at millimeter-wave frequencies. A piezo-driven millimeter-wave tuning mechanism is designed to compensate for the fabrication and assembly tolerances and reduces the complexity of the manufacturing process. Full article

(This article belongs to the Special Issue Application and Technology Trends in Optoelectronic Sensors)

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15 pages, 2840 KiB

Open AccessArticle

Photoacoustic-MR Image Registration Based on a Co-Sparse Analysis Model to Compensate for Brain Shift

by Parastoo Farnia, Bahador Makkiabadi, Maysam Alimohamadi, Ebrahim Najafzadeh, Maryam Basij, Yan Yan, Mohammad Mehrmohammadi and Alireza Ahmadian

Sensors 2022, 22(6), 2399; https://doi.org/10.3390/s22062399 - 21 Mar 2022

Cited by 5 | Viewed by 2180

Abstract

Brain shift is an important obstacle to the application of image guidance during neurosurgical interventions. There has been a growing interest in intra-operative imaging to update the image-guided surgery systems. However, due to the innate limitations of the current imaging modalities, accurate brain [...] Read more.

Brain shift is an important obstacle to the application of image guidance during neurosurgical interventions. There has been a growing interest in intra-operative imaging to update the image-guided surgery systems. However, due to the innate limitations of the current imaging modalities, accurate brain shift compensation continues to be a challenging task. In this study, the application of intra-operative photoacoustic imaging and registration of the intra-operative photoacoustic with pre-operative MR images are proposed to compensate for brain deformation. Finding a satisfactory registration method is challenging due to the unpredictable nature of brain deformation. In this study, the co-sparse analysis model is proposed for photoacoustic-MR image registration, which can capture the interdependency of the two modalities. The proposed algorithm works based on the minimization of mapping transform via a pair of analysis operators that are learned by the alternating direction method of multipliers. The method was evaluated using an experimental phantom and ex vivo data obtained from a mouse brain. The results of the phantom data show about 63% improvement in target registration error in comparison with the commonly used normalized mutual information method. The results proved that intra-operative photoacoustic images could become a promising tool when the brain shift invalidates pre-operative MRI. Full article

(This article belongs to the Section Biomedical Sensors)

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Figure 1
Brain-mimicking phantom design and fabrication. (a) The dimensions of the phantom were about 150 × 40 mm, (b) a 3D model of the phantom including two simulated vessels with 1.2 and 1.4 mm inside diameters were inserted randomly into the phantom. (c) The cross-section of the phantom with vessels filled using two different contrast agents CuSO4 (H2O)5 and human blood. Full article ">Figure 2
Schematic of the PA imaging setup, which includes a tunable pulsed laser and a programmable ultrasound data acquisition system. Full article ">Figure 3
Ex vivo head of mouse data: (a) MR image and (b) PA image. Five registration targets are shown in red and blue markers in (a,b), respectively, to assess the performance of the registration algorithm [<a href="#B67-sensors-22-02399" class="html-bibr">67</a>]. Full article ">Figure 4
(a) Pre-operative MR image, (b) intra-operative MR image, and (c) brain deformation field was achieved by registration of intra-operative and pre-operative MR images using residual complexity method. Full article ">Figure 5
The workflow for automatic multi-modal image registration to compensate for brain deformation. MR and PA images including pre-defined targets were set as a reference and float images, respectively. After applying brain deformation on PA images, registration of MR and deformed PA was conducted and evaluated. Full article ">Figure 6
The results of multi-modal image registration of phantom data. First row: original image of phantom data before deformation from three different modalities: (a) MRI, (b) US, and (c) PA; second row: deformed images of (d) MRI, (e) US, and (f) PA. The third row shows the results of registered images of (g) MR-MR, (h) US-MR, and (i) PA-MR using the NMI algorithm. The last row shows the results of registered images of (j) MR-MR, (k) US-MR, and (l) PA-MR using JACSM. The blue arrows in the third and last rows represent the surface of the phantom in different modalities. Blue arrows A are related to the surface of the phantom in original MR images and blue arrows B are related to the surface of the phantom in deformed MR, deformed US, and deformed PA images. White arrows in (i,l) show that the PA-MR registration results for vessels were located in the depth of the phantom. Full article ">Figure 7
The results of multi-modal image registration of mouse brain data: (a) MRI, (b) PA image, (c) PA image after applying non-linear deformation, and (d) registration of deformed PA and MRI of mouse data. Registration of MRI images before and after deformation was shown in (e) as a gold standard. Panel (f) shows the mean of RMSE, TRE, and HD of PA-MR image registration for all data of the mouse brain. Full article ">

19 pages, 438 KiB

Open AccessArticle

Joint Resource Allocation in Secure OFDM Two-Way Untrusted Relay System

by Yifeng Jin, Xunan Li, Guocheng Lv, Meihui Zhao and Ye Jin

Sensors 2022, 22(6), 2398; https://doi.org/10.3390/s22062398 - 21 Mar 2022

Viewed by 1795

Abstract

The security issue of wireless communication is a common concern because of its broadcast nature, especially when the relay becomes an eavesdropper. In the orthogonal frequency division multiplexing (OFDM) relay system, when the relay is untrusted, the security of the system faces serious [...] Read more.

The security issue of wireless communication is a common concern because of its broadcast nature, especially when the relay becomes an eavesdropper. In the orthogonal frequency division multiplexing (OFDM) relay system, when the relay is untrusted, the security of the system faces serious threats. Although there exist some resource allocation schemes in a single-carrier system with untrusted relaying, it is difficult to apply them to the multi-carrier system. Hence, a resource allocation scheme for the multi-carrier system is needed. Compared to the one-way relay system, a two-way relay system can improve the data transmission efficiency. In this paper, we consider joint secure resource allocation for a two-way cooperative OFDM system with an untrusted relay. The joint resource allocation problem of power allocation and subcarrier pairing is formulated to maximize the sum secrecy rate of the system under individual power constraints. To solve the non-convex problem efficiently, we propose an algorithm based on the alternative optimization method. The proposed algorithm is evaluated by simulation results and compared with the benchmarks in the literature. According to the numerical results, in a high signal-to-noise ratio (SNR) scenario, the proposed algorithm improves the achievable sum secrecy rate of the system by more than 15% over conventional algorithms. Full article

(This article belongs to the Special Issue Security and Communication Networks)

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An OFDM two-way system with an untrusted relay. Solid lines: signal transmission on subcarriers in the first slot. Dashed lines: signal forward transmission on subcarriers in the second slot. Full article ">Figure 2
Flowchart of the proposed algorithm. Full article ">Figure 3
Sum secrecy rate versus transmit power per node when N = 16. Full article ">Figure 4
Sum secrecy rate versus number of subcarriers when transmit power per node is 20 dBm. Full article ">Figure 5
Allocated power versus index of subcarriers when transmit power per node is 20 dBm; N = 8. Full article ">Figure 6
Sum secrecy rate versus distance from user <math display="inline"><semantics> <mi mathvariant="normal">A</mi> </semantics></math> to the relay <math display="inline"><semantics> <mi mathvariant="normal">R</mi> </semantics></math> when N = 16 and transmit power per node is 20 dBm. Full article ">Figure 7
Sum secrecy rate versus transmit power of relay <math display="inline"><semantics> <mi mathvariant="normal">R</mi> </semantics></math> when N = 16 and transmit power of user nodes is 20 dBm. Full article ">

24 pages, 10918 KiB

Open AccessReview

Concise Historic Overview of Strain Sensors Used in the Monitoring of Civil Structures: The First One Hundred Years

by Branko Glisic

Sensors 2022, 22(6), 2397; https://doi.org/10.3390/s22062397 - 20 Mar 2022

Cited by 35 | Viewed by 4544

Abstract

Strain is one of the most frequently monitored parameters in civil structural health monitoring (SHM) applications, and strain-based approaches were among the first to be explored and applied in SHM. There are multiple reasons why strain plays such an important role in SHM: [...] Read more.

Strain is one of the most frequently monitored parameters in civil structural health monitoring (SHM) applications, and strain-based approaches were among the first to be explored and applied in SHM. There are multiple reasons why strain plays such an important role in SHM: strain is directly related to stress and deflection, which reflect structural performance, safety, and serviceability. Strain field anomalies are frequently indicators of unusual structural behaviors (e.g., damage or deterioration). Hence, the earliest concepts of strain sensing were explored in the mid-XIX century, the first effective strain sensor appeared in 1919, and the first onsite applications followed in the 1920′s. Today, one hundred years after the first developments, two generations of strain sensors, based on electrical and fiber-optic principles, firmly reached market maturity and established themselves as reliable tools applied in strain-based SHM. Along with sensor developments, the application methods evolved: the first generation of discrete sensors featured a short gauge length and provided a basis for local material monitoring; the second generation greatly extended the applicability and effectiveness of strain-based SHM by providing long gauge and one-dimensional (1D) distributed sensing, thus enabling global structural and integrity monitoring. Current research focuses on a third generation of strain sensors for two-dimensional (2D) distributed and quasi-distributed sensing, based on new advanced technologies. On the occasion of strain sensing centenary, and as an homage to all researchers, practitioners, and educators who contributed to strain-based SHM, this paper presents an overview of the first one hundred years of strain sensing technological progress, with the objective to identify relevant transformative milestones and indicate possible future research directions. Full article

(This article belongs to the Special Issue Section “Sensor Networks”: 10th Anniversary)

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18 pages, 7473 KiB

Open AccessArticle

Investigation of the Temperature Compensation of Piezoelectric Weigh-In-Motion Sensors Using a Machine Learning Approach

by Hailu Yang, Yue Yang, Yue Hou, Yue Liu, Pengfei Liu, Linbing Wang and Yuedong Ma

Sensors 2022, 22(6), 2396; https://doi.org/10.3390/s22062396 - 20 Mar 2022

Cited by 8 | Viewed by 2849

Abstract

Piezoelectric ceramics have good electromechanical coupling characteristics and a high sensitivity to load. One typical engineering application of piezoelectric ceramic is its use as a signal source for Weigh-In-Motion (WIM) systems in road traffic monitoring. However, piezoelectric ceramics are also sensitive to temperature, [...] Read more.

Piezoelectric ceramics have good electromechanical coupling characteristics and a high sensitivity to load. One typical engineering application of piezoelectric ceramic is its use as a signal source for Weigh-In-Motion (WIM) systems in road traffic monitoring. However, piezoelectric ceramics are also sensitive to temperature, which affects their measurement accuracy. In this study, a new piezoelectric ceramic WIM sensor was developed. The output signals of sensors under different loads and temperatures were obtained. The results were corrected using polynomial regression and a Genetic Algorithm Back Propagation (GA-BP) neural network algorithm, respectively. The results show that the GA-BP neural network algorithm had a better effect on sensor temperature compensation. Before and after GA-BP compensation, the maximum relative error decreased from about 30% to less than 4%. The sensitivity coefficient of the sensor reduced from 1.0192 × 10⁻²/°C to 1.896 × 10⁻⁴/°C. The results show that the GA-BP algorithm greatly reduced the influence of temperature on the piezoelectric ceramic sensor and improved its temperature stability and accuracy, which helped improve the efficiency of clean-energy harvesting and conversion. Full article

(This article belongs to the Section Electronic Sensors)

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11 pages, 2462 KiB

Open AccessCommunication

Diagnosis of Partial Discharge Based on the Air Components for the 10 kV Air-Insulated Switchgear

by Qipeng Tan, Tiandong Zhang, Shaocheng Wu, Jiachen Gao and Bin Song

Sensors 2022, 22(6), 2395; https://doi.org/10.3390/s22062395 - 20 Mar 2022

Cited by 6 | Viewed by 2650

Abstract

Partial discharge (PD) is a common phenomenon of insulation aging in air-insulated switchgear and will change the gas composition in the equipment. However, it is still a challenge to diagnose and identify the defect types of PD. This paper conducts enclosed experiments based [...] Read more.

Partial discharge (PD) is a common phenomenon of insulation aging in air-insulated switchgear and will change the gas composition in the equipment. However, it is still a challenge to diagnose and identify the defect types of PD. This paper conducts enclosed experiments based on gas sensors to obtain the concentration data of the characteristic gases CO, NO₂, and O₃ under four typical defects. The random forest algorithm with grid search optimization is used for fault identification to explore a method of identifying defect types through gas concentration. The results show that the gases concentration variations do have statistical characteristics, and the RF algorithm can achieve high accuracy in prediction. The combination of a sensor and a machine learning algorithm provides the gas component analysis method a way to diagnose PD in an air-insulated switchgear. Full article

(This article belongs to the Special Issue Sensors for Measurements and Diagnostic in Electrical Power Systems)

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17 pages, 62958 KiB

Open AccessArticle

Phase Optimization for Multipoint Haptic Feedback Based on Ultrasound Array

by Zhili Long, Shuyuan Ye, Zhao Peng, Yuyang Yuan and Zhuohua Li

Sensors 2022, 22(6), 2394; https://doi.org/10.3390/s22062394 - 20 Mar 2022

Viewed by 2131

Abstract

Ultrasound-based haptic feedback is a potential technology for human–computer interaction (HCI) with the advantages of a low cost, low power consumption and a controlled force. In this paper, phase optimization for multipoint haptic feedback based on an ultrasound array was investigated, and the [...] Read more.

Ultrasound-based haptic feedback is a potential technology for human–computer interaction (HCI) with the advantages of a low cost, low power consumption and a controlled force. In this paper, phase optimization for multipoint haptic feedback based on an ultrasound array was investigated, and the corresponding experimental verification is provided. A mathematical model of acoustic pressure was established for the ultrasound array, and then a phase-optimization model for an ultrasound transducer was constructed. We propose a pseudo-inverse (PINV) algorithm to accurately determine the phase contribution of each transducer in the ultrasound array. By controlling the phase difference of the ultrasound array, the multipoint focusing forces were formed, leading to various shapes such as geometries and letters, which can be visualized. Because the unconstrained PINV solution results in unequal amplitudes for each transducer, a weighted amplitude iterative optimization was deployed to further optimize the phase solution, by which the uniform amplitude distributions of each transducer were obtained. For the purpose of experimental verification, a platform of ultrasound haptic feedback consisting of a Field Programmable Gate Array (FPGA), an electrical circuit and an ultrasound transducer array was prototyped. The haptic performances of a single point, multiple points and dynamic trajectory were verified by controlling the ultrasound force exerted on the liquid surface. The experimental results demonstrate that the proposed phase-optimization model and theoretical results are effective and feasible, and the acoustic pressure distribution is consistent with the simulation results. Full article

(This article belongs to the Special Issue Biological, Liquid and Gas Sensors Based on Piezoelectric Resonators)

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