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Search Results (462)

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Keywords = distributed fiber-optic sensor

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41 pages, 10236 KiB  
Review
Coaxial Cable Distributed Strain Sensing: Methods, Applications and Challenges
by Stephanie King, Gbanaibolou Jombo, Oluyomi Simpson, Wenbo Duan and Adrian Bowles
Sensors 2025, 25(3), 650; https://doi.org/10.3390/s25030650 - 22 Jan 2025
Viewed by 301
Abstract
Distributed strain sensing is a powerful tool for in situ structural health monitoring for a wide range of critical engineering infrastructures. Strain information from a single sensing device can be captured from multiple locations simultaneously, offering a reduction in hardware, wiring, installation costs, [...] Read more.
Distributed strain sensing is a powerful tool for in situ structural health monitoring for a wide range of critical engineering infrastructures. Strain information from a single sensing device can be captured from multiple locations simultaneously, offering a reduction in hardware, wiring, installation costs, and signal analysis complexity. Fiber optic distributed strain sensors have been the widely adopted approach in this field, but their use is limited to lower strain applications due to the fragile nature of silica fiber. Coaxial cable sensors offer a robust structure that can be adapted into a distributed strain sensor. They can withstand greater strain events and offer greater resilience in harsh environments. This paper presents the developments in methodology for coaxial cable distributed strain sensors. It explores the two main approaches of coaxial cable distributed strain sensing such as time domain reflectometry and frequency domain reflectometry with applications. Furthermore, this paper highlights further areas of research challenges in this field, such as the deconvolution of strain and temperature effects from coaxial cable distributed strain sensor measurements, mitigating the effect of dielectric permittivity on the accuracy of strain measurements, addressing manufacturing challenges with the partial reflectors for a robust coaxial cable sensor, and the adoption of data-driven analysis techniques for interrogating the interferogram to eliminate concomitant measurement effects with respect to temperature, dielectric permittivity, and signal-to-noise ratio, amongst others Full article
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19 pages, 6460 KiB  
Article
Research on Numerical Simulation and Interpretation Method of Water Injection Well Temperature Field Based on DTS
by Shengzhe Shi, Junfeng Liu, Ming Li, Chao Sun and Tong Lei
Processes 2025, 13(1), 274; https://doi.org/10.3390/pr13010274 - 19 Jan 2025
Viewed by 378
Abstract
Traditional water injection profile monitoring primarily relies on methods such as isotope tracers and oxygen activation. Conventional resistive temperature instruments, which are drag-measured, are highly sensitive to production interference and can only capture the transient temperature response of the wellbore at a single [...] Read more.
Traditional water injection profile monitoring primarily relies on methods such as isotope tracers and oxygen activation. Conventional resistive temperature instruments, which are drag-measured, are highly sensitive to production interference and can only capture the transient temperature response of the wellbore at a single depth. As a result, the temperature data obtained from well temperature logging has certain limitations. Using DTS (Distributed Temperature Sensing) for pre-and post-well opening and shut-in water injection profile testing, along with quantitative analysis of water absorption, addresses the limitations of traditional well temperature logging, which typically offers only qualitative insights. However, the interpretation of DTS data still requires further refinement to improve its alignment with actual conditions. In this study, COMSOL software 6.1 was used to simulate the temperature distribution within the downhole temperature field, both spatially and temporally. The Sobol method was employed to analyze the influence of fluid flow rate and rock thermal conductivity on the temperature field. The results indicated that the fluid flow rate in the wellbore has a more significant impact and is the primary controlling factor of the downhole temperature field. Based on actual field conditions and the forward simulation results, the differential evolution algorithm was applied to invert and interpret the water injection profile. The inversion results showed minimal error, confirming the feasibility of this approach. It is helpful to interpret the well temperature profile measured by the distributed fiber optic temperature sensor, which is helpful to improve the ability of well temperature logging to identify the output profile, which has important academic value and practical significance for the development of water injection wells. Full article
(This article belongs to the Section Energy Systems)
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20 pages, 9576 KiB  
Article
Movement of Overlying Strata and Mechanical Responses of Shallow Buried Gas Pipelines in Coal Mining Areas
by Jiashu Han, Zhanguo Ma, Junyu Sun, Peng Gong, Pengfei Yan, Chuanchuan Cai, Mingshuo Xu and Tianqi She
Appl. Sci. 2025, 15(2), 622; https://doi.org/10.3390/app15020622 - 10 Jan 2025
Viewed by 395
Abstract
Damage to buried gas pipelines caused by mining activities has been frequently reported. Based on a case study from the Central China coal mining area, this research employs a scaled model experiment to investigate the movement of overlying strata in a room-and-pillar mining [...] Read more.
Damage to buried gas pipelines caused by mining activities has been frequently reported. Based on a case study from the Central China coal mining area, this research employs a scaled model experiment to investigate the movement of overlying strata in a room-and-pillar mining goaf. Distributed optical fiber strain sensors and thin-film pressure sensors were used to simultaneously measure the stress variations in the pipeline and changes in the soil pressure surrounding it. As the mining recovery rate increased from 50% to 86%, the maximum displacement of the overburden sharply escalated from 33.55 mm to 79.19 mm. During surface subsidence, separation between the pipeline and surrounding soil was observed, leading to the formation of a soil-arching effect. The development of the soil-arching effect increased soil pressure on the top of the pipeline, while soil pressure at the bottom of the pipeline increased on the outer side of the subsidence area and decreased on the inner side. Three critical sections of the pipeline were identified, with the maximum stress reaching 1908.41 kPa. After the completion of mining activities, pipeline collapse occurred, leading to a weakening of the soil-arching effect. Consequently, both stress concentration in the pipeline and soil pressure decreased. The probability integral method was corrected by incorporating the fracture angle, which enabled the determination of the location of maximum surface subsidence curvature, found to be close to the three failure sections of the pipeline. Full article
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21 pages, 8579 KiB  
Article
Laboratory Tests Using Distributed Fiber Optical Sensors for Strain Monitoring
by Rodrigo Moraes da Silveira, Marcelo Buras, André Luiz Delmondes Pereira Filho, Juliana Ferreira Fernandes and Marcos Massao Futai
Sensors 2025, 25(2), 324; https://doi.org/10.3390/s25020324 - 8 Jan 2025
Viewed by 385
Abstract
Using fiber optics as a tool for different kinds of geotechnical monitoring can be highly attractive and cost-effective when compared to conventional instruments, such as piezometers and inclinometers, among others. A single fiber optic cable may cover a larger monitoring area compared to [...] Read more.
Using fiber optics as a tool for different kinds of geotechnical monitoring can be highly attractive and cost-effective when compared to conventional instruments, such as piezometers and inclinometers, among others. A single fiber optic cable may cover a larger monitoring area compared to conventional instrumentation and allows for monitoring more than one physical quantity with the same fiber optic cable. The literature provides several different examples of distributed fiber optic systems usage. For using any sensor, a calibration curve and parameters are required. In the case of strain sensors, calibration is required to derive strain values from the frequency measurement quantity. However, fiber optic sensor cable manufacturers do not often provide cable calibration parameters, and researchers should consult the specialized literature. This article thus presents a bench adjusted for tests with single-mode fiber optic cables, as well as results of tensile tests for defining the function of strain variations in two different optical fiber cables manufactured by different companies using two different distributed interrogators. This paper also proposes a methodology for calibrating fiber optic cable deformation. A few manufacturers of fiber optic cables aim at civil engineering applications. Therefore, we propose a calibration methodology to show the possibility of obtaining calibration parameters of any fiber optic cable, even those manufactured for telecommunications purposes and not only for cables manufactured for civil engineering use. Thus, researchers will not be restricted to the acquisition of special cables for their applications. The results allowed us to conclude that the application of calibrated fiber optic sensors to experimental pile foundations permits the evaluation of the load–displacement behavior of these elements under different loading conditions. Full article
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16 pages, 5055 KiB  
Article
A Millimeter-Resolution Operando Thermal Image of Prismatic Li-Ion Batteries Using a Distributed Optical Fiber Sensor
by Zhen Guo, Mina Abedi Varnosfaderani, Calum Briggs, Erdogan Guk and James Marco
Batteries 2025, 11(1), 19; https://doi.org/10.3390/batteries11010019 - 8 Jan 2025
Viewed by 458
Abstract
With the demand for energy gravimetric and volumetric density in electrical vehicles, lithium-ion batteries are undergoing a trend toward larger formats, along with maximized cell-to-pack efficiency. Current battery thermal management systems and battery modeling, relying on point measurement (thermocouples/thermistors), face challenges in providing [...] Read more.
With the demand for energy gravimetric and volumetric density in electrical vehicles, lithium-ion batteries are undergoing a trend toward larger formats, along with maximized cell-to-pack efficiency. Current battery thermal management systems and battery modeling, relying on point measurement (thermocouples/thermistors), face challenges in providing comprehensive characterization for larger batteries and extensive monitoring across the pack. Here, we proposed a novel Rayleigh-scattering-based distributed optical fiber sensor to deliver thermal images of a large prismatic cell. Using an optical fiber of 1 mm diameter wrapped around the cell, the optical sensor delivered over 400 unique measurement locations at 3 mm spatial resolution. During a 1.0 C charge, the optical-measured maximum temperature difference was 8.2 °C, while point-like thermocouples, located at the cell front surface and rear surface center, only had a 0.8 °C maximum temperature difference. Moreover, the all-surface-covered optical sensor identified hotspot generation around the vicinity of the tabs, highlighting the essential role of tabs. The maximum temperature on the negative current tab reached 113.9 °C during a 1.5 C discharge, while the hottest spot on the cell surface was only 52.1 °C. This was further validated by the operando thermal image in both the time domain and the spatial domain, facilitating a detailed analysis of the thermal-behavior-like heat generation on the current tabs, transmission through the surface, and dissipation to the cell bottom. Full article
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22 pages, 6678 KiB  
Article
Monitoring Excavation-Induced Deformation of a Secant Pile Wall Using Distributed Fiber Optic Sensors
by Chengyu Hong, Chengkai Xu, Weibin Chen, Jianwei Liu and Junkun Tan
Sensors 2025, 25(1), 254; https://doi.org/10.3390/s25010254 - 4 Jan 2025
Viewed by 477
Abstract
This paper investigates the use of the BOTDA (Brillouin Optical Time-Domain Analysis) technology to monitor a large-scale bored pile wall in the field. Distributed fiber optic sensors (DFOSs) were deployed to measure internal temperature and strain changes during cement grouting, hardening, and excavation-induced [...] Read more.
This paper investigates the use of the BOTDA (Brillouin Optical Time-Domain Analysis) technology to monitor a large-scale bored pile wall in the field. Distributed fiber optic sensors (DFOSs) were deployed to measure internal temperature and strain changes during cement grouting, hardening, and excavation-induced deformation of a secant pile wall. The study details the geological conditions and DFOS installation process. During grouting, the temperature increased by approximately 69 °C due to cement hydration 30 min post-grouting, while the strain decreased by 0.5% on average due to cement slurry shrinkage. During excavation, the temperature changes were minimal, but the excavation depth significantly influenced the strain distribution, with continuous compressive deformation observed in two monitored boreholes. Two analytical methods, the numerical integration method (NIM) and the finite difference method (FDM), were used to calculate the lateral pile displacement based on the monitored strain data. The results were compared with previous monitoring data, showing that the lateral displacement of the pile was minimal after excavation and was attributed to the high stiffness of the secant pile wall. This study demonstrates the effectiveness of DFOSs and BOTDA technology for monitoring complex pile wall behaviors during construction. Full article
(This article belongs to the Special Issue Novel Sensor Technologies for Civil Infrastructure Monitoring)
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17 pages, 5679 KiB  
Article
Fiber Bragg Grating Thermometry and Post-Treatment Ablation Size Analysis of Radiofrequency Thermal Ablation on Ex Vivo Liver, Kidney and Lung
by Sanzhar Korganbayev, Leonardo Bianchi, Clara Girgi, Elva Vergantino, Domiziana Santucci, Eliodoro Faiella and Paola Saccomandi
Sensors 2025, 25(1), 245; https://doi.org/10.3390/s25010245 - 3 Jan 2025
Viewed by 810
Abstract
Radiofrequency ablation (RFA) is a minimally invasive procedure that utilizes localized heat to treat tumors by inducing localized tissue thermal damage. The present study aimed to evaluate the temperature evolution and spatial distribution, ablation size, and reproducibility of ablation zones in ex vivo [...] Read more.
Radiofrequency ablation (RFA) is a minimally invasive procedure that utilizes localized heat to treat tumors by inducing localized tissue thermal damage. The present study aimed to evaluate the temperature evolution and spatial distribution, ablation size, and reproducibility of ablation zones in ex vivo liver, kidney, and lung using a commercial device, i.e., Dophi™ R150E RFA system (Surgnova, Beijing, China), and to compare the results with the manufacturer’s specifications. Optical fibers embedding arrays of fiber Bragg grating (FBG) sensors, characterized by 0.1 °C accuracy and 1.2 mm spatial resolution, were employed for thermometry during the procedures. Experiments were conducted for all the organs in two different configurations: single-electrode (200 W for 12 min) and double-electrode (200 W for 9 min). Results demonstrated consistent and reproducible ablation zones across all organ types, with variations in temperature distribution and ablation size influenced by tissue characteristics and RFA settings. Higher temperatures were achieved in the liver; conversely, the lung exhibited the smallest ablation zone and the lowest maximum temperatures. The study found that using two electrodes for 9 min produced larger, more rounded ablation areas compared to a single electrode for 12 min. Our findings support the efficacy of the RFA system and highlight the need for tailored RFA parameters based on organ type and tumor properties. This research provides insights into the characterization of RFA systems for optimizing RFA techniques and underscores the importance of accurate thermometry and precise procedural planning to enhance clinical outcomes. Full article
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17 pages, 4769 KiB  
Article
Intelligent Pattern Recognition Using Distributed Fiber Optic Sensors for Smart Environment
by Brian Pamukti, Shofuro Afifah, Shien-Kuei Liaw, Jiun-Yu Sung and Daping Chu
Sensors 2025, 25(1), 47; https://doi.org/10.3390/s25010047 - 25 Dec 2024
Viewed by 425
Abstract
Distributed fiber optic sensors (DFOSs) have become increasingly popular for intrusion detection, particularly in outdoor and restricted zones. Enhancing DFOS performance through advanced signal processing and deep learning techniques is crucial. While effective, conventional neural networks often involve high complexity and significant computational [...] Read more.
Distributed fiber optic sensors (DFOSs) have become increasingly popular for intrusion detection, particularly in outdoor and restricted zones. Enhancing DFOS performance through advanced signal processing and deep learning techniques is crucial. While effective, conventional neural networks often involve high complexity and significant computational demands. Additionally, the backscattering method requires the signal to travel twice the normal distance, which can be inefficient. We propose an innovative interferometric sensing approach utilizing a Mach–Zehnder interferometer (MZI) combined with a time forest neural network (TFNN) for intrusion detection based on signal patterns. This method leverages advanced sensor characterization techniques and deep learning to improve accuracy and efficiency. Compared to the conventional one-dimensional convolutional neural network (1D-CNN), our proposed approach achieves an 8.43% higher accuracy, demonstrating the significant potential for real-time signal processing applications in smart environments. Full article
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12 pages, 4355 KiB  
Article
Effect of Seepage on Sand Levee Failure Due to Lateral Overtopping
by Woochul Kang, Seongyun Kim and Eunkyung Jang
Water 2024, 16(24), 3617; https://doi.org/10.3390/w16243617 - 16 Dec 2024
Viewed by 478
Abstract
Recent increases in rainfall duration and intensity due to climate change have heightened the importance of levee stability. However, previous studies on levee failure, primarily caused by seepage and overtopping, have mostly examined these causes independently owing to their distinct characteristics. In this [...] Read more.
Recent increases in rainfall duration and intensity due to climate change have heightened the importance of levee stability. However, previous studies on levee failure, primarily caused by seepage and overtopping, have mostly examined these causes independently owing to their distinct characteristics. In this study, we conducted lateral overtopping failure experiments under seepage conditions that closely resembled those in experiments conducted in previous studies. Seepage was monitored using water pressure sensors and a distributed optical fiber cable that provided continuous heat for temperature monitoring in the levee. Τhe analysis of levee failure due to lateral overtopping, in the presence of seepage, was conducted using image analysis with digitization techniques and machine learning-based color segmentation techniques on the protected lowland side of the levee, targeting the same area. The results revealed that levee failure occurred more than twice as fast in experiments where seepage conditions were considered compared to the experiments where they were not. Thus, levees weakened by seepage are more vulnerable to overtopping and breaching. Consequently, employing a comprehensive approach that integrates various monitoring and analysis methods for assessing levee stability is preferable to relying on a single method alone. Full article
(This article belongs to the Special Issue Safety Monitoring of Hydraulic Structures)
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13 pages, 3213 KiB  
Article
Tailored Compositions of Ni-Ti-Sn Nanopowders Deposited on Polymer Fiber Optics Through Flash Evaporation
by Elango Natarajan, Anil Chouhan, Santheraleka Ramanathan, Kalaimani Markandan, Santhosh Mozhuguan Sekar, Chun Kit Ang, Nagarajan Deivanayagampillai and Gérald Franz
J. Compos. Sci. 2024, 8(12), 526; https://doi.org/10.3390/jcs8120526 - 13 Dec 2024
Viewed by 470
Abstract
Fiber coatings protect the glass surface of fiber from extrinsic environmental factors. The coating of shape memory alloy over fiber is useful in sensor fabrication where the state of deformation is affected by the phase transformation of the coated material. In addition, coated [...] Read more.
Fiber coatings protect the glass surface of fiber from extrinsic environmental factors. The coating of shape memory alloy over fiber is useful in sensor fabrication where the state of deformation is affected by the phase transformation of the coated material. In addition, coated plastic fibers can be used in elevated temperature environments. To this end, the present research aims to investigate the effect of the Ni-Ti-Sn composite coating over the fiber. Homogeneous particle distribution, agglomeration, porosity and the ability to obtain uniform coating thickness have been general concerns in fiber coatings. Hence, the present study comprehensively investigated the mechanical and thermal behavior as well as morphological properties of Ni-Ti-Sn nanopowders deposited on polymer fiber optics. Five sets of polyamide-coated samples with different Ni-Ti-Sn proportions were fabricated and characterized. Morphological studies confirmed that an even coating thickness enhanced the mechanical integrity and optical performance. The optimum composition demonstrated superior tensile strength of 29.5 MPa and a 25% increase in elongation compared to the uncoated sample. The Ni-Ti-Sn alloy composition investigated in the present study is promising for industrial applications where thermal stability and mechanical performance are warranted. Full article
(This article belongs to the Special Issue Polymer Composites and Fibers, 3rd Edition)
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14 pages, 4193 KiB  
Article
Simultaneous Temperature and Relative Humidity Measurement Using Machine Learning in Rayleigh-Based Optical Frequency Domain Reflectometry
by Mateusz Mądry, Bogusław Szczupak, Mateusz Śmigielski and Bartosz Matysiak
Sensors 2024, 24(24), 7913; https://doi.org/10.3390/s24247913 - 11 Dec 2024
Viewed by 600
Abstract
This paper presents, for the first time to the best of our knowledge, simultaneous temperature and relative humidity (RH) measurement using a machine learning (ML) model in Rayleigh-based Optical Frequency Domain Reflectometry (OFDR). The sensor unit consists of two segments: bare and polyimide-coated [...] Read more.
This paper presents, for the first time to the best of our knowledge, simultaneous temperature and relative humidity (RH) measurement using a machine learning (ML) model in Rayleigh-based Optical Frequency Domain Reflectometry (OFDR). The sensor unit consists of two segments: bare and polyimide-coated fibers, each with different sensitivities to temperature. The polyimide-coated fiber is RH-sensitive, unlike the bare fiber. We propose the ML approach to avoid manual post-processing data and maintain relatively high accuracy of the sensor. The root mean square error (RMSE) values for the 3 cm length of the sensor unit were 0.36 °C and 1.73% RH for temperature and RH, respectively. Furthermore, we investigated the impact of sensor unit lengths and number of data points on RMSE values. This approach eliminates the need for manual data processing, reduces analysis time, and enables accurate, simultaneous measurement of temperature and RH in Rayleigh-based OFDR. Full article
(This article belongs to the Section Optical Sensors)
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15 pages, 2203 KiB  
Article
OpticalTrust: A Sensor-to-Blockchain Framework Using Free-Space Optical Communication
by Parveen Bajaj, Aman Kataria, Vikram Puri, Sachin Gupta and Hong Min
Sensors 2024, 24(23), 7797; https://doi.org/10.3390/s24237797 - 5 Dec 2024
Viewed by 670
Abstract
In the dynamic landscape of the tech industry, the escalating requirement for swift and secure data transmission has catalyzed innovation in integrated communication systems. Free-Space Optics (FSOs) has emerged as a promising contender in optical communications. While conventional optical fiber systems can achieve [...] Read more.
In the dynamic landscape of the tech industry, the escalating requirement for swift and secure data transmission has catalyzed innovation in integrated communication systems. Free-Space Optics (FSOs) has emerged as a promising contender in optical communications. While conventional optical fiber systems can achieve bit rates of up to 40 Gbps with proper design, they are limited primarily by electronics rather than semiconductor laser capabilities. This study presents an integrated framework that combines FSOs, blockchain technology, and sensor networks to address challenges in data transmission, security, and environmental adaptation. This study analyzes FSOs system performance through the Quality (Q) Factor and Bit Error Rate (BER), comparing systems with and without Erbium-Doped Fiber Amplifiers (EDFAs) across various bit rates (8, 12, 16, and 20 Gbps) and transmission distances (5–25 km). To enhance data security and reliability, a blockchain architecture is incorporated with smart contracts and an InterPlanetary File System (IPFS) for storing and validating results generated from FSOs simulation. Additionally, this study explores the design of sensor network models for FSOs technology by investigating how distributed sensor arrays can be theoretically integrated with FSOs systems, with testing focused on FSOs performance and blockchain implementation. Full article
(This article belongs to the Section Optical Sensors)
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23 pages, 8360 KiB  
Article
Weak Fiber Bragg Grating Array-Based In Situ Flow and Defects Monitoring During the Vacuum-Assisted Resin Infusion Process
by Xiao Liu, Zuoyin Tang, Xin Gui, Wenchang Yin, Jingyi Cao, Zhigang Fang and Zhengying Li
Sensors 2024, 24(23), 7637; https://doi.org/10.3390/s24237637 - 29 Nov 2024
Viewed by 537
Abstract
Monitoring of real-time flow and defects in the vacuum-assisted resin infusion (VARI) process can provide important guidelines for full impregnation of dry reinforcement. A weak fiber Bragg grating array was employed to obtain quasi-distributed monitoring results in real-time. Sensitivity testing of different kinds [...] Read more.
Monitoring of real-time flow and defects in the vacuum-assisted resin infusion (VARI) process can provide important guidelines for full impregnation of dry reinforcement. A weak fiber Bragg grating array was employed to obtain quasi-distributed monitoring results in real-time. Sensitivity testing of different kinds of coated optical fiber sensors (OFs) was carried out first, and the polyacrylate-coated OF showed a greater wavelength-shift response than the polyimide-coated one. Then, two- and three-dimensional flow monitoring tests were carried out. During the resin-filling stage, three trends of strain curve were identpified in relation to the different placement setups of embedded OFs, the resin flow direction, and the different vacuum-bagging methods. The monitoring criteria were analyzed and the results were compared with the visual inspection, showing good agreement and indicating the ability of the fiber Bragg grating array. Finally, defects including dry spots and voids were introduced and reflected in the maximum changed strains of FBGs due to the smaller stress relaxation, indicating the potential to characterize the local flow state and permeabilities experimentally based on these quasi-distributed sensing methods. Full article
(This article belongs to the Section Optical Sensors)
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32 pages, 32247 KiB  
Article
Safety Dynamic Monitoring and Rapid Warning Methods for Mechanical Shaft
by Hui Wang, Xinlong Li, Weilong Wen, Gaoyu Liu, Jian Chen and Huawei Tong
Buildings 2024, 14(12), 3756; https://doi.org/10.3390/buildings14123756 - 25 Nov 2024
Viewed by 488
Abstract
In the context of urban space constraints, subway and underground projects have become crucial strategies to alleviate urban congestion and enhance residents’ quality of life. However, pit engineering, a frequent accident area in geotechnical engineering, urgently requires innovative safety monitoring technologies. Traditional monitoring [...] Read more.
In the context of urban space constraints, subway and underground projects have become crucial strategies to alleviate urban congestion and enhance residents’ quality of life. However, pit engineering, a frequent accident area in geotechnical engineering, urgently requires innovative safety monitoring technologies. Traditional monitoring methods face challenges such as high labor costs, lengthy monitoring cycles, high-risk working environments, and over-reliance on human judgment. To address these issues, this paper introduces an innovative monitoring system integrating Fiber Bragg Grating (FBG) sensing technology based on a subway pit project in Guangzhou. This system not only achieves fully automated data acquisition but also includes an intelligent monitoring cloud platform, providing unprecedented automated and intelligent monitoring solutions for support structures and the surrounding environment during mechanical shaft construction. The key findings of this paper include the following: (1) The breakthrough application of distributed optical fiber monitoring technology, including successfully deploying this advanced technology in complex pit engineering environments, enabling the precise and continuous monitoring of support structures and surrounding changes, and demonstrating its high effectiveness and intelligence in practical engineering. (2) The innovative design of an intelligent safety monitoring system. By integrating sensors and wireless communication technology, an efficient data networking architecture is constructed, supporting remote configuration and flexible adjustment of monitoring equipment, significantly enhancing data collection‘s real-time performance and continuity while greatly reducing safety risks for field staff, achieving an intelligent upgrade of monitoring work. (3) Comprehensive and accurate empirical analysis. During shaft excavation, the monitoring data collected by the system were stable and reliable, with all indicators maintained within reasonable ranges and closely matching expected changes caused by construction activities, validating the system’s practical application effectiveness in complex construction environments and providing a scientific basis for pit engineering safety management. Full article
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31 pages, 870 KiB  
Article
Advances in Data Pre-Processing Methods for Distributed Fiber Optic Strain Sensing
by Bertram Richter, Lisa Ulbrich, Max Herbers and Steffen Marx
Sensors 2024, 24(23), 7454; https://doi.org/10.3390/s24237454 - 22 Nov 2024
Cited by 1 | Viewed by 780
Abstract
Because of their high spatial resolution over extended lengths, distributed fiber optic sensors (DFOS) enable us to monitor a wide range of structural effects and offer great potential for diverse structural health monitoring (SHM) applications. However, even under controlled conditions, the useful signal [...] Read more.
Because of their high spatial resolution over extended lengths, distributed fiber optic sensors (DFOS) enable us to monitor a wide range of structural effects and offer great potential for diverse structural health monitoring (SHM) applications. However, even under controlled conditions, the useful signal in distributed strain sensing (DSS) data can be concealed by different types of measurement principle-related disturbances: strain reading anomalies (SRAs), dropouts, and noise. These disturbances can render the extraction of information for SHM difficult or even impossible. Hence, cleaning the raw measurement data in a pre-processing stage is key for successful subsequent data evaluation and damage detection on engineering structures. To improve the capabilities of pre-processing procedures tailored to DSS data, characteristics and common remediation approaches for SRAs, dropouts, and noise are discussed. Four advanced pre-processing algorithms (geometric threshold method (GTM), outlier-specific correction procedure (OSCP), sliding modified z-score (SMZS), and the cluster filter) are presented. An artificial but realistic benchmark data set simulating different measurement scenarios is used to discuss the features of these algorithms. A flexible and modular pre-processing workflow is implemented and made available with the algorithms. Dedicated algorithms should be used to detect and remove SRAs. GTM, OSCP, and SMZS show promising results, and the sliding average is inappropriate for this purpose. The preservation of crack-induced strain peaks’ tips is imperative for reliable crack monitoring. Full article
(This article belongs to the Section Optical Sensors)
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