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The temperature response of pavement is not only crucial for assessing the internal stresses within pavement structures but is also an essential parameter in pavement design. Investigating the temperature response of rubberized concrete pavements (RCP) can support the construction of large-scale rubber concrete pavements. This study constructed a pavement monitoring system based on fiber Bragg grating technology to investigate the temperature distribution, temperature strain, temperature effects, and temperature stress of RCP. The results show that the daily temperature–time history curves of concrete pavement exhibit a significant asymmetry, with the heating phase accounting for only one-third of the curve. The temperature at the middle of RCP is 1.8 °C higher than that of ordinary concrete pavement (OCP). The temperature distribution along the thickness of the pavement follows a "spindle-shaped" pattern, with higher temperatures in the center and lower temperatures at the ends. Additionally, the addition of rubber aggregates increases the temperature strain in the pavements, makes the temperature–strain hysteresis effect more pronounced, and increases the curvature of the pavement slab. However, the daily stress range at the bottom of RCP is approximately 0.7 times that of OCP. [ABSTRACT FROM AUTHOR]

Fiber-optic sensors, such as fiber Bragg grating (FBG) sensors and fiber-optic interferometers, have excellent sensing capabilities for industrial, chemical, and biomedical engineering applications. This paper used machine learning to enhance the number of fiber-optic sensing placement points and promote the cost-effectiveness and diversity of fiber-optic sensing applications. In this paper, the framework adopted is the FBG cascading an interferometer, and a deep belief network (DBN) is used to demodulate the wavelength of the sampled complex spectrum. As the capacity of the fiber-optic sensor arrangement is optimized, the peak spectra from FBGs undergoing strain or temperature changes may overlap. In addition, overlapping FBG spectra with interferometer spectra results in periodic modulation of the spectral intensity, making the spectral intensity variation more complex as a function of different strains or temperature levels. Therefore, it may not be possible to analyze the sensed results of FBGs with the naked eye, and it would be ideal to use machine learning to demodulate the sensed results of FBGs and the interferometer. Experimental results show that DBN can successfully interpret the wavelengths of individual FBG peaks, and peaks of the interferometer spectrum, from the overlapping spectrum of peak-overlapping FBGs and the interferometer. [ABSTRACT FROM AUTHOR]

As the main force-bearing component of cable-stayed bridges, cables are often in complex and harsh working environments, and traditional cable force monitoring methods have certain limitations. A fiber grating cable force sensor was developed by encapsulating the fiber grating sensor embedded into the groove on the metal pressure block, and the durability performance of two epoxy resin adhesive encapsulated fiber grating cable force sensors in the acid and alkali corrosion environment was studied, and then the sensor life prediction equation was derived by relying on the inverse power law model and aging kinetic theory. The test results show that the sensor perform well on the linearity and stability, and the main reason for the failure of the sensor in the corrosion solution is the corrosion and peeling of the adhesive in the boundary zone of the package site. The acid and alkali resistance of class A sensors is stronger than that of class B sensors, and the service life of class A sensors in weak acid and weak alkali environments is more than 35 years, which is longer than the average cable change life of cable-stayed bridge cables of 20 years, and can realize the monitoring of the whole life cycle of cables. [ABSTRACT FROM AUTHOR]

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A two-stage decoupling model based on an artificial neural network with polynomial regression is proposed for the six-component force sensor load decoupling problem in the case of multidimensional mixed loading. The six-dimensional load categorization stage model constructed in the first stage combines 63 load category label sets with a deep BP neural network. The six-dimensional load regression stage model was constructed by combining polynomial regression with a BP neural network in the second stage. Meanwhile, the six-component force sensor with a fiber Bragg grating (FBG) sensor as the sensitive element was designed, and the elastomer simulation and calibration experimental dataset was established to realize the validation of the two-stage decoupling model. The results based on the simulation data show that the accuracy of the classification stage is 93.65%. The MAPE for the force channel in the regression stage is 6.29%, and 3.24% for the moment channel. The results based on experimental data show that the accuracy of the classification stage is 87.80%. The MAPE for the force channel in the regression phase is 5.63%, and 4.82% for the moment channel. [ABSTRACT FROM AUTHOR]

A low-velocity impact event can produce undetectable damages inside laminated composite structures. Such damages have been introduced as one of the main causes of catastrophic failure of whole structure, thus impact event detection and localization should be essential for many kinds of composite structures. In this study, low-velocity impact localization method was proposed using six multiplexed fiber Bragg grating (FBG) sensors on the composite wingbox structure. The principle is to find the location which has the most similar set of reference signals from the database. Firstly, the required reference signals were measured to construct the database for the test section which is located on the upper skin of the wingbox. Then, the localization was implemented with the process of detecting the time of arrival (TOA) and finding the impact location. The similarities between the impact-induced signals and reference signals are assessed by calculating the root mean squared (RMS) values. Through the impact localizations on the non-reference locations, this method was validated. Also, this method was applied to the impact localizations when the wingbox structure was under static loads. From the acceptable results of such experiments under static loading conditions, the practicality of this method was successfully verified. [ABSTRACT FROM AUTHOR]

This study proposes the utilization of an optical fiber vibration sensor for detecting the superposition of extremely close frequencies in vibration signals. Integration of deep neural networks (DNN) proves to be meaningful and efficient, eliminating the need for signal analysis methods involving complex mathematical calculations and longer computation times. Simulation results of the proposed model demonstrate the remarkable capability to accurately distinguish frequencies below 1 Hz. This underscores the effectiveness of the proposed image-based vibration signal recognition system embedded in DNN as a streamlined yet highly accurate method for vibration signal detection, applicable across various vibration sensors. Both simulation and experimental evaluations substantiate the practical applicability of this integrated approach, thereby enhancing electric motor vibration monitoring techniques. [ABSTRACT FROM AUTHOR]

The construction of steel pipe piles combined with side grouting is regarded as an effective way to improve the uplift bearing capacity of piles for transmission towers in rugged mountainous areas. This new piling technology involves the injection of grout into the annular space between the steel pipe pile and the side boundary of the pre-dug hole, which aims to improve the properties of soil-pile interface. However, to date, there are few studies on the soil-pile interface property and uplift failure model of this new kind of steel pipe piles with side grouting. In this study, the shear properties of the grouting interface between soil and steel plate were investigated, and then compared with the shear tests of undisturbed plastic clay and gravel clayey soil. It is indicated that the shear strength of the grouting interface between soil and steel plate is less than that of corresponding undisturbed soils. In addition, the uplift loading test about two grouted implantation steel pipe piles (GISPP) instrumented with Fiber Bragg Grating (FBG) sensors in plastic clay and gravel clayey soil was carried out, which demonstrates that the failure surface of GISPP mainly occurs in the interface of soil and grouting body. The grouting body can be well bonded to the steel pipe pile after uplift, but the ground surface around the GISPP presents a conical failure model. Finally, a new method considering the conical failure model was proposed to calculate the ultimate uplift capacity of GISPP, which was validated to be efficient and reliable compared with previous calculation methods.

The use of smart healthcare systems to monitor cardiac parameters has gained widespread popularity globally due to advancements in technology. The Internet of Medical Things (IoMT) has become an integral part of modern healthcare by facilitating the efficient monitoring of vital signs through advanced sensors. Heart Rate variability (HRV) characteristics, which provide valuable insights into a patient's health, have become indispensable in healthcare applications. Fiber Bragg Grating (FBG) based optical sensors have emerged as cutting-edge technology for continuous monitoring of several cardiac parameters among the new alternatives. Recent technical advances have improved the accuracy of these sensors, allowing for the early identification and prognosis of heart illnesses, potentially saving lives. This article delves into the design, construction, and structural analysis of a passive optical FBG sensor capable of real-time acquisition of HRV parameters such as standard Deviation of Normal-to-Normal (SDNN), Root Mean Square of Successive Differences (RMSSD), and Percentage of Successive Normal-to-Normal intervals (PNN50) differing by more than 50 ms, along with Heart Rate (HR). It also provides enhanced signal processing methods as well as an IoT-based architectural architecture. Experimental research in a laboratory including five participants (three males and two females) revealed good performance, with an error rate of less than 10 percent when compared to a typical HR monitor. This intelligent technology detects arrhythmia, coronary heart disease, aortic disorders, and strokes with high accuracy, providing a substantial contribution to healthcare. The combination of Fiber Bragg Grating (FBG) sensors, Internet of Things (IoT) architecture, and cutting-edge technology has enormous potential for improving cardiac monitoring and patient outcomes. [ABSTRACT FROM AUTHOR]

Due to attractive application in the medical field, fiber Bragg grating sensor has become increasing attractive from past few decades for various strain sensing applications. FBG sensor has been used in many applications such as different surgical devices, vital sign detection devices, invasive surgery, heart rate, dental applications and biosensing application as wearable sensing devices. This paper reviews the 55 recent research articles published on fiber Bragg grating sensor for biomedical application used the qualitative, quantitative and experimental method to identify the recent advancement and challenges. In this study, particular focus is placed on applications for biomechanical devices, temperature monitors, respiratory monitors, and biosensing applications. Critical things, demands, and emerging trends for these sensing devices are also discussed in order to determine what will be needed for the next generation. [ABSTRACT FROM AUTHOR]

The additive noise in the condition monitoring system using fiber Bragg grating (FBG) sensors, including white Gaussian noise and multifrequency interference, has a significantly negative influence on the fault diagnosis of rotating machinery. Spectral subtraction (SS) is an effective method for handling white Gaussian noise. However, the SS method exhibits poor performance in eliminating multifrequency interference because estimating the noise spectrum accurately is difficult, and it significantly weakens the useful information components in measured signals. In this study, an improved spectral subtraction (ISS) method is proposed to enhance its denoising performance. In the ISS method, a reference noise signal measured by the same sensing system without working loads is considered the estimated noise, the same sliding window is used to divide the power spectrums of the measured and reference noise signals into multiple frequency bands, and the formula of spectral subtraction in the standard SS method is modified. A simulation analysis and an experiment are executed by using simulated signals and establishing a vibration test rig based on the FBG sensor, respectively. The statistical results demonstrate the effectiveness and feasibility of the ISS method in simultaneously eliminating white Gaussian noise and multifrequency interference while well maintaining the useful information components. [ABSTRACT FROM AUTHOR]

The carbonation of concrete greatly affects its service life. In this paper, fiber Bragg grating (FBG) sensors were used to investigate the relationship between concrete carbonation and its mechanical properties. A T130 High Sensitivity Strain Cable Sensor with a good linearity was used to monitor the internal strain in concrete, to investigate the variation in the elastic modulus of concrete with carbonation time. A mathematical model of elastic modulus and carbonation time of concrete based on FBG was established. At the same time, the authors explored the relationship between the carbonation depth and compressive strength of concrete and the carbonation time using a phenolphthalein solution test and a compressive strength test, respectively. The experimental results indicate that the carbonation depth, compressive strength, and elastic modulus of concrete increase with carbonation time. In the early stage of carbonation, these three parameters increase rapidly, while they grow slowly in the later stage of carbonation. The varying trend of the elastic modulus of concrete is consistent with the compressive strength, which shows a binomial relationship. Therefore, the elastic modulus, measured using FBG sensors, is used as an indicator of the characterization of the carbonation resistance of concrete. This work provides a new approach for concrete carbonation detection and assessment. [ABSTRACT FROM AUTHOR]

The temperature response of pavement is not only crucial for assessing the internal stresses within pavement structures but is also an essential parameter in pavement design. Investigating the temperature response of rubberized concrete pavements (RCP) can support the construction of large-scale rubber concrete pavements. This study constructed a pavement monitoring system based on fiber Bragg grating technology to investigate the temperature distribution, temperature strain, temperature effects, and temperature stress of RCP. The results show that the daily temperature–time history curves of concrete pavement exhibit a significant asymmetry, with the heating phase accounting for only one-third of the curve. The temperature at the middle of RCP is 1.8 °C higher than that of ordinary concrete pavement (OCP). The temperature distribution along the thickness of the pavement follows a “spindle-shaped” pattern, with higher temperatures in the center and lower temperatures at the ends. Additionally, the addition of rubber aggregates increases the temperature strain in the pavements, makes the temperature–strain hysteresis effect more pronounced, and increases the curvature of the pavement slab. However, the daily stress range at the bottom of RCP is approximately 0.7 times that of OCP.

Fiber-optic sensors, such as fiber Bragg grating (FBG) sensors and fiber-optic interferometers, have excellent sensing capabilities for industrial, chemical, and biomedical engineering applications. This paper used machine learning to enhance the number of fiber-optic sensing placement points and promote the cost-effectiveness and diversity of fiber-optic sensing applications. In this paper, the framework adopted is the FBG cascading an interferometer, and a deep belief network (DBN) is used to demodulate the wavelength of the sampled complex spectrum. As the capacity of the fiber-optic sensor arrangement is optimized, the peak spectra from FBGs undergoing strain or temperature changes may overlap. In addition, overlapping FBG spectra with interferometer spectra results in periodic modulation of the spectral intensity, making the spectral intensity variation more complex as a function of different strains or temperature levels. Therefore, it may not be possible to analyze the sensed results of FBGs with the naked eye, and it would be ideal to use machine learning to demodulate the sensed results of FBGs and the interferometer. Experimental results show that DBN can successfully interpret the wavelengths of individual FBG peaks, and peaks of the interferometer spectrum, from the overlapping spectrum of peak-overlapping FBGs and the interferometer.

Fiber-reinforced plastic (FRP) is prone to invisible damage caused by low-velocity impact (LVI) during service. The structural health monitoring system is of great significance for damage monitoring and maintenance of composite materials. In this study, four fiber Bragg grating sensors were employed to collect the time domain strain signals of composite materials subjected to LVIs. Furthermore, a numerical simulation model was established to rapidly obtain impact signal dataset. The signal arrival time, peak time, and peak amplitude were selected as signal features, and the backpropagation neural network was successfully applied to determine the location and energy of LVIs. To address the issue of peak feature extraction in the strain signal processing, a genetic algorithm-based sliding window peak detection optimization method was proposed, which significantly improved the final prediction accuracy. The experimental results indicated that within a position range of 300 mm × 300 mm, the average positioning error can reach 5.1 mm; and in an energy range of 0.5–1 J, the average energy prediction error can reach 0.030 J. The proposed method achieved accurate identification of the LVI location and energy for FRP.

Weigh-in-motion (WIM) systems are essential for efficient transportation and monitoring parameters such as vehicle number, speed, and weight to ensure regulatory compliance and enhance road safety. Recently, WIM measurements using the Glass Fiber Reinforced Polymer Fiber Bragg Grating (GFRP-FBG) sensors have shown robustness and effectiveness. However, the accuracy of weight evaluation using the WIM systems based on GFRP-FBG sensors can be significantly influenced by the vehicle-wandering effect, which introduces uncertainties in wheel position determination and weight calculations. This paper assessed the impact of vehicle wandering on the accuracy of a WIM measurement system based on GFRP-FBG sensors by utilizing a new hybrid sensor-camera system that integrates roadside cameras and in-pavement GFRP-FBG sensors. The detailed methodology and framework of the developed hybrid system are introduced, followed by field testing on Highway I-94 in the United States. The field testing results indicate that by using the hybrid system, the wheel load detection accuracy of the WIM system based on GFRP-FBG sensors can be controlled to be a Type I or Type III WIM according to the ASTM 1318E-09 standard, with an average accuracy ranging from 87.83% to 94.65%. At the same time, when the wander distance is less than or equal to 9 cm, the developed WIM system proves to be very cost-effective as it only comprises two GFRP-FBG sensors, one temperature FBG sensor, and one camera. These findings indicate the practical potential to enhance the accuracy of WIM systems based on GFRP-FBG sensors designed for highways for low-coast, reliable, and accurate measurements by addressing vehicle wandering effects. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study assesses fault deformation morphology under supercritical CO 2 leakage. • The internal-external strain variation is evaluated in faults under SC-CO 2 leakage. • The viscosity indicates that T 0 = 45 °C is the critical temperature. • The distribution of P - T zones may be used as a criterion for fault leakage. For the long-term safe operation of carbon capture and storage (CCS) projects, the leakage of supercritical carbon dioxide (SC-CO 2) along a fault is an important factor that needs to be monitored. To investigate the phase change and fault deformation associated with SC-CO 2 leakage along a fault, this study carried out five groups of SC-CO 2 leakage experiments at different initial CO 2 temperatures. The volume of the CO 2 storage container (100 mL), CO 2 initial pressure (8.07 MPa) and fault confining pressure (10.5 MPa) were controlled at the same values. The CO 2 phase change and fault internal-external strains response were monitored by high-precision fiber Bragg grating sensors throughout the experiment. The results show that (1) Temperature and strains response times were 1 and 2.5 times longer than pressure, respectively. (2) The viscosity greatly influenced the determination of the critical temperature T 0 = 45 °C. (3) The fault internal strains were more than twice that of the external one; except for the entrance, the fault internal and external strains states were opposite at the beginning of leakage; all other positions on the fault surface showed compressive strains except for the tensile strains at the entrance. (4) The distribution of the inflection point of temperature–pressure curves may be used as a basis for distinguishing CO 2 leakage from faults (near the triple point) or pipes (far from the triple point). This study provides technical and theoretical support for laboratory-scale studies on the mechanism of internal and external strains differences caused by phase transition of SC-CO 2 leakage along faults. [ABSTRACT FROM AUTHOR]

The traditional convergence instrument, 3D laser scanning and other monitoring technologies for the deformation of surrounding rock in the mine roadway can not meet the comprehensive monitoring requirements of complex projects. The technologies have low real-time and automatic monitoring degree, and do not have the capability of long-distance, high-precision and large-area monitoring. The existing optical fiber sensing technology only monitors the single parameter of the surrounding rock in the roadway. It can not comprehensively analyze the stability of the surrounding rock in the roadway. Taking the main adit of a coal mine as the engineering background, the stability of surrounding rock before and after the filling above the adit is studied by numerical simulation. The results show that the filling engineering causes the bearing pressure of surrounding rock on both sides of the adit to rise with asymmetric distribution. The maximum subsidence of the top plate increases from 8.3 mm before filling to 22.1 mm. The maximum floor heave increases from 4.0 mm to 8.5 mm. The maximum increase of the displacement of the two sides is 16.2 mm. The deformation of the surrounding rock corresponds strongly to the bearing pressure, which increases with the thickness of the filling above the adit. The fiber Bragg grating (FBG) sensor is used to construct the adit surrounding rock deformation monitoring system. The FBG sensor is set at the adit section to monitor the opening of the adit arch crown crack, the deformation of the roof, floor and both sides, and the stress and strain of the section. The local deformation of the surrounding rock is analyzed through the real-time spectrum. The results show that the adit roof is obviously under pressure under the influence of the disturbance of the overburden load under the existing condition of stone masonry arch support. The maximum subsidence of the roof is about 30 mm, forming a crack about 2 mm wide. The monitoring results are consistent with the numerical simulation and field observation results. The result verifies the effectiveness of the FBG-based adit surrounding rock stability monitoring method. According to the monitoring results, the reinforcement support scheme of bolt+T-shaped steel plate is proposed for the weak part of the adit support. The support effect is verified by numerical simulation. The results show that after the optimized support scheme, the maximum subsidence of the adit roof under the disturbance of overburden load is 11.3 mm. The maximum displacement of the two sides is 12.04 mm, and the average reduction of the surrounding rock deformation is 48.8%. The scheme improves the stability of the surrounding rock.

A two-stage decoupling model based on an artificial neural network with polynomial regression is proposed for the six-component force sensor load decoupling problem in the case of multidimensional mixed loading. The six-dimensional load categorization stage model constructed in the first stage combines 63 load category label sets with a deep BP neural network. The six-dimensional load regression stage model was constructed by combining polynomial regression with a BP neural network in the second stage. Meanwhile, the six-component force sensor with a fiber Bragg grating (FBG) sensor as the sensitive element was designed, and the elastomer simulation and calibration experimental dataset was established to realize the validation of the two-stage decoupling model. The results based on the simulation data show that the accuracy of the classification stage is 93.65%. The MAPE for the force channel in the regression stage is 6.29%, and 3.24% for the moment channel. The results based on experimental data show that the accuracy of the classification stage is 87.80%. The MAPE for the force channel in the regression phase is 5.63%, and 4.82% for the moment channel.

This study proposes the utilization of an optical fiber vibration sensor for detecting the superposition of extremely close frequencies in vibration signals. Integration of deep neural networks (DNN) proves to be meaningful and efficient, eliminating the need for signal analysis methods involving complex mathematical calculations and longer computation times. Simulation results of the proposed model demonstrate the remarkable capability to accurately distinguish frequencies below 1 Hz. This underscores the effectiveness of the proposed image-based vibration signal recognition system embedded in DNN as a streamlined yet highly accurate method for vibration signal detection, applicable across various vibration sensors. Both simulation and experimental evaluations substantiate the practical applicability of this integrated approach, thereby enhancing electric motor vibration monitoring techniques.

Lumbar puncture is a minimally invasive procedure that utilizes a spinal needle to puncture the lumbar epidural space to take a sample from the cerebrospinal fluid or inject drugs for diagnostic and therapeutic purposes. Physicians rely on their expertise to localize epidural space. Due to its critical procedure, the failure rate can reach up to 28%. Hence, a high level of experience and caution is required to correctly insert the needle without puncturing the dura mater, which is a fibrous layer protecting the spinal cord. Failure of spinal anesthesia is, in some cases, related to faulty needle placement techniques since it is blindly inserted. Therefore, advanced techniques for localization of the epidural space are essential to avoid any possible side effects. As for epidural space localization, various ideas were carried out over recent years to provide accurate identification of the epidural space. Subsequently, several methodologies based on mechanical and optical schemes have been proposed. Several research groups worked from different aspects of the problem, namely, the clinical and engineering sides. Hence, the main goal of this paper is to review this research with the aim of remedying the gap between the clinical side of the problem and the engineering side by examining the main techniques in building sensors for such purposes. This manuscript provides an understanding of the clinical needs of spinal needles from an anatomical point of view. Most importantly, it discusses the mechanical and optical approaches in designing and building sensors to guide spinal needles. Finally, the standards that must be followed in building smart spinal needles for approval procedures are also presented, along with some insight into future directions. [ABSTRACT FROM AUTHOR]

In view of the frequent occurrence of pavement diseases in arid areas with large temperature difference, the central and western regions of Inner Mongolia was taken as an example, and the characteristics of environment and pavement diseases were deeply investigated. Fiber grating sensors were embedded in the composite base asphalt pavement structure of the new expressway. The strain response of different directions and depths of the pavement structure were investigated through field loading tests. The fatigue life of the pavement structure was calculated according to the measured results to verify the practical application effect of the composite base structure. Results show that the daily temperature difference and annual difference in the central and western regions of Inner Mongolia exceed 84% of the whole country, and the annual rainfall is lower than 87. 4% of the whole country. The primary pavement disease is reflective cracking, and the crack spacing is only 10 ~20 m. The strain changes of the bottom surface layer and the upper base layer of the composite base pavement structure under traffic load are obvious, and the lateral strain fluctuates more and recovers slower than the longitudinal strain, thus the dominant disease of the pavement structure under the combined effects of load and temperature is lateral cracking. After adding the ATB-25 upper base layer, the strain under the standard axial load is reduced by 40% ~50%, and the peak strain is 39 με. The calculated fatigue life of the pavement structure is 24 368 × 10 6 times, which can control the construction cost and avoid the risk of fatigue cracking in the operation period. [ABSTRACT FROM AUTHOR]

This article investigated the structure and packaging features of Bi–B–Zn sealing glass with Bi 2 O 3 concentrations ranging from 38 to 63 (wt %). The results indicate that when Bi 2 O 3 and the Bi/B ratio grow, the glass transition temperature (Tg) and the glass softening temperature changes correspondingly, with the lowest values occurring when the Bi/B ratio is 4. Both the infrared and Raman spectra demonstrate that the [BiO] units and [BO] units in the glass network structure increase or decrease when the Bi/B ratio increases. This modification will lower the number of broken bonds during the transition and crystallization process, hence increasing the stability of the oxide glass. The polyimide optical fiber etched with Fiber Bragg Grating (FBG) was encapsulated on 65-manganese steel, an elastic material. The results indicate that the residual pre-stress before and after encapsulation reaches 1.4 nm when the Bi/B ratio is 4 and that the encapsulation performance is commensurate with the material structure analysis results. A good glass penetration distance helps the bonding effect of the sealing glass, as seen by the microstructure of the bonding interface. At ambient temperature, the average tensile force of a G04 sample bonded with optical fiber was 2.72 N. The samples were then placed in a tube furnace replicating a high-temperature subterranean environment for an extended duration. According to the findings, the FBG sensor is capable of stable sensing. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a submersible permanent magnet synchronous motor (SPMSM) must function in downhole high temperature crude oil for long periods of time, the accurate prediction of its temperature rise is crucial to improve the stability of the motor. However, the analysis of its temperature field involves multiple physical fields, such as the electric field, the magnetic field, the fluid field and so on, and it is difficult to calculate accurately. Motor loss is usually loaded as a fixed value when calculating the temperature field, while in reality, the loss always changes with temperature. Therefore, the calculation of temperature is inaccurate using this one-way coupled method. In this paper, the relationship between loss and temperature is investigated and an electromagnetic-thermal fluid multi-physics two-way coupled analysis method suitable for SPMSM is proposed. The loss can be loaded as a variable by this new two-way coupled method, which significantly improves the temperature calculation accuracy. In order to prove the feasibility of the two-way coupled method, experiments based of a prototype of high torque and low speed SPMSM and cavity pump are conducted with the fiber Bragg grating (FBG) sensor measuring SPMSM temperature. Finally, the multi-physics two-way coupled method proposed in this paper is proven to be rational and feasible in the analysis of the SPMSM temperature rise. [ABSTRACT FROM AUTHOR]

The additive noise in the condition monitoring system using fiber Bragg grating (FBG) sensors, including white Gaussian noise and multifrequency interference, has a significantly negative influence on the fault diagnosis of rotating machinery. Spectral subtraction (SS) is an effective method for handling white Gaussian noise. However, the SS method exhibits poor performance in eliminating multifrequency interference because estimating the noise spectrum accurately is difficult, and it significantly weakens the useful information components in measured signals. In this study, an improved spectral subtraction (ISS) method is proposed to enhance its denoising performance. In the ISS method, a reference noise signal measured by the same sensing system without working loads is considered the estimated noise, the same sliding window is used to divide the power spectrums of the measured and reference noise signals into multiple frequency bands, and the formula of spectral subtraction in the standard SS method is modified. A simulation analysis and an experiment are executed by using simulated signals and establishing a vibration test rig based on the FBG sensor, respectively. The statistical results demonstrate the effectiveness and feasibility of the ISS method in simultaneously eliminating white Gaussian noise and multifrequency interference while well maintaining the useful information components.

The carbonation of concrete greatly affects its service life. In this paper, fiber Bragg grating (FBG) sensors were used to investigate the relationship between concrete carbonation and its mechanical properties. A T130 High Sensitivity Strain Cable Sensor with a good linearity was used to monitor the internal strain in concrete, to investigate the variation in the elastic modulus of concrete with carbonation time. A mathematical model of elastic modulus and carbonation time of concrete based on FBG was established. At the same time, the authors explored the relationship between the carbonation depth and compressive strength of concrete and the carbonation time using a phenolphthalein solution test and a compressive strength test, respectively. The experimental results indicate that the carbonation depth, compressive strength, and elastic modulus of concrete increase with carbonation time. In the early stage of carbonation, these three parameters increase rapidly, while they grow slowly in the later stage of carbonation. The varying trend of the elastic modulus of concrete is consistent with the compressive strength, which shows a binomial relationship. Therefore, the elastic modulus, measured using FBG sensors, is used as an indicator of the characterization of the carbonation resistance of concrete. This work provides a new approach for concrete carbonation detection and assessment.

The airborne distributed Position and Orientation System (POS) is a key piece of equipment for providing high-precision motion parameters for aerial remote sensing systems. However, wing deformation degrades the performance of distributed POS, thus, it is urgent to obtain high-precision deformation information to assist distributed POS. In this study, a modeling and calibrating method of fiber Bragg grating (FBG) sensors for wing deformation displacement measurement is proposed. First, based on the cantilever beam theory and piecewise superposition, a modeling and calibrating method for wing deformation displacement measurement is established. The wing is then placed under different deformation conditions, and the changes in the wing deformation displacement and corresponding wavelength variations of the pasted FBG sensors are obtained using theodolite coordinate measurement system and FBG demodulator, respectively. Subsequently, linear least square fitting is deployed to develop the relationship model between the wavelength variations of the FBG sensors and wing deformation displacement. Finally, the wing deformation displacement at the measuring point in the temporal and spatial dimensions is obtained by fitting and interpolation. An experiment is conducted, and the results show that the accuracy of the proposed method can reach 0.721 mm with a wing length of 3 m, which can be used in the motion compensation of an airborne distributed POS.

The morphing wing trailing edge is an attractive aviation structure due to its shape-adaptive ability, which can effectively improve the aerodynamic performance of an aircraft throughout the whole flight. In this paper, a mechanical solution for a variable camber trailing edge (VCTE) based on a multi-block rotating rib is proposed. Parametric optimizations are conducted to achieve the smooth and continuous deformation of the morphing rib. A prototype is designed according to the optimized results. In addition, the deformations of the trailing edge are monitored via an indirect method using a fiber Bragg grating (FBG) sensor beam. Finally, ground tests are performed to investigate the morphing capacity of the VCTE and the shape monitoring ability of the proposed method. Our results indicate that a maximum deflection range from 5° upward to 15° downward can be obtained for the VCTE and the indirect sensing system can satisfactorily monitor the deformation of the trailing edge. [ABSTRACT FROM AUTHOR]

Weigh-in-motion (WIM) systems are essential for efficient transportation and monitoring parameters such as vehicle number, speed, and weight to ensure regulatory compliance and enhance road safety. Recently, WIM measurements using the Glass Fiber Reinforced Polymer Fiber Bragg Grating (GFRP-FBG) sensors have shown robustness and effectiveness. However, the accuracy of weight evaluation using the WIM systems based on GFRP-FBG sensors can be significantly influenced by the vehicle-wandering effect, which introduces uncertainties in wheel position determination and weight calculations. This paper assessed the impact of vehicle wandering on the accuracy of a WIM measurement system based on GFRP-FBG sensors by utilizing a new hybrid sensor-camera system that integrates roadside cameras and in-pavement GFRP-FBG sensors. The detailed methodology and framework of the developed hybrid system are introduced, followed by field testing on Highway I-94 in the United States. The field testing results indicate that by using the hybrid system, the wheel load detection accuracy of the WIM system based on GFRP-FBG sensors can be controlled to be a Type I or Type III WIM according to the ASTM 1318E-09 standard, with an average accuracy ranging from 87.83% to 94.65%. At the same time, when the wander distance is less than or equal to 9 cm, the developed WIM system proves to be very cost-effective as it only comprises two GFRP-FBG sensors, one temperature FBG sensor, and one camera. These findings indicate the practical potential to enhance the accuracy of WIM systems based on GFRP-FBG sensors designed for highways for low-coast, reliable, and accurate measurements by addressing vehicle wandering effects.

The long-term application of Fiber Bragg Grating strain sensors is seriously affected by the severe airborne environmental conditions in the structure state monitoring of civil aircraft. To evaluate the airborne environmental adaptability of sensors, the airborne environmental conditions are analyzed, and the sensing characteristics are proposed as the evaluation index. The sensing characteristics evaluation index includes the sensitivity coefficient, linearity, zero drift and the temperature coefficient. And then a sensor effectiveness test method based on the equal strength beam was designed before and after the environmental test. Two types of Fiber Bragg Grating sensor, with coating and non-metallic substrate encapsulation, were used respectively. After 14 environmental tests, the problems of the sensors were exposed and the environmental adaptability of the sensors was analyzed. The experiment results show that the proposed index system can effectively evaluate the failure status of sensors, and all of these prove that the environmental adaptability analysis method is feasible. [ABSTRACT FROM AUTHOR]

For subway safety, it is important to monitor the convergence deformation of shield tunnels in the long term. However, traditional monitoring methods are constrained by high cost and technical difficulties. Herein, improvements achieved through use of a new type of optical fiber (OF) sensor are reported. The new type of optical fiber sensor, namely, the flexible long-gauge Fiber Bragg Grating (FBG) sensor, is proposed with descriptions of design, preparation and strain sensing performance. Then, a method of assessing convergence deformation is proposed based on distributed long-gauge strain measurements. Finally, the proposed method is validated with measurements made on two full size specimens of shield segments. It is also concluded that the seam change shows a strong influence on convergence deformation. From static experiments, convergence deformation can be accurately evaluated to satisfy the demands of tunnel management. Considering the additional advantages of distributed sensing, such as sensing distance, stability and durability, the proposed method exhibits broad application prospects. [ABSTRACT FROM AUTHOR]

Lumbar puncture is a minimally invasive procedure that utilizes a spinal needle to puncture the lumbar epidural space to take a sample from the cerebrospinal fluid or inject drugs for diagnostic and therapeutic purposes. Physicians rely on their expertise to localize epidural space. Due to its critical procedure, the failure rate can reach up to 28%. Hence, a high level of experience and caution is required to correctly insert the needle without puncturing the dura mater, which is a fibrous layer protecting the spinal cord. Failure of spinal anesthesia is, in some cases, related to faulty needle placement techniques since it is blindly inserted. Therefore, advanced techniques for localization of the epidural space are essential to avoid any possible side effects. As for epidural space localization, various ideas were carried out over recent years to provide accurate identification of the epidural space. Subsequently, several methodologies based on mechanical and optical schemes have been proposed. Several research groups worked from different aspects of the problem, namely, the clinical and engineering sides. Hence, the main goal of this paper is to review this research with the aim of remedying the gap between the clinical side of the problem and the engineering side by examining the main techniques in building sensors for such purposes. This manuscript provides an understanding of the clinical needs of spinal needles from an anatomical point of view. Most importantly, it discusses the mechanical and optical approaches in designing and building sensors to guide spinal needles. Finally, the standards that must be followed in building smart spinal needles for approval procedures are also presented, along with some insight into future directions.

To realize continuous real-time monitoring of the large-scale internal strain field of coal and rock mass, a bidirectional strain sensor based on FBGs encapsulated using a hollow cylindrical steel tube was designed. The sensor's structural parameters were optimized through unidirectional loading, and the strain change laws of the sensor were analyzed under unidirectional and bidirectional loading conditions, in which the stress-strain fitting curves of the sensor and the relationships of the strain in the vertical and horizontal directions were obtained under different lateral pressure loading conditions. A similar theoretical model was established to verify the accuracy of the linear relationship between the surrounding rock stress and the strain measured by the sensor system. [ABSTRACT FROM AUTHOR]

Fiber Bragg grating sensors (FBGs) are considered a valid sensing solution for a variety of medical applications. The last decade witnessed the exploitation of these sensors in applications ranging from minimally invasive surgery to biomechanics and monitoring physiological parameters. Recently, preliminary studies investigated the potential impact of FBGs in the management of epidural procedures by detecting when the needle reaches the epidural space with the loss of resistance (LOR) technique. In this article, we propose a soft and flexible FBG-based system capable of detecting the LOR, we optimized the solution by considering different designs and materials, and we assessed the feasibility of the optimized soft sensor (SS) in clinical settings. The proposed SS addresses some of the open challenges in the use of a sensing solution during epidural punctures: it has high sensitivity, it is non-invasive, the sensing element does not need to be inserted within the needle, and the clinician can follow the standard clinical practice. Our analysis highlights how the material and the design impact the system response, and thus its performance in this scenario. We also demonstrated the system's feasibility of detecting the LOR during epidural procedures. [ABSTRACT FROM AUTHOR]

Background: To develop wearable healthcare sensors that use fiber Bragg grating (FBG) sensors, a stretch textile product with an embedded FBG sensor is required.Objective: The FBG sensor, which is an optical fiber, was embedded into a textile product following a wavy pattern by using a warp knitting machine.Methods: When an optical fiber is embedded in a textile product, the effect of the cycle length of wavy pattern and the number of cycles on the optical loss is verified. The shorter the cycle length of the wavy pattern of the optical fiber, and more increase in the number of cycles, the longer the textile product in which the optical fiber is embedded can expand and contract. However, when the cycle length of the wave pattern is 30 mm (shortest), large in optical loss, the pulse wave signal cannot be measured. If the cycle length of the wavy pattern is 50 mm or more, small in optical loss, the pulse wave signal is measured.Results: Compared with a straight pattern embedding FBG sensor, the amplitude value of the pulse wave signal measured with a cycle length of 50 mm is large, therefore the sensor sensitivity in this state is greater. This result is consistent with the measurement sensitivity depending on the angle of installation with respect to the direction of the artery.Conclusion: With a cycle length of wavy pattern of 50 mm and 4 cycles, a stretch textile product with an embedded FBG sensor can be fabricated. Pulse wave signals are measured with this textile product, and the development of wearable healthcare sensors is expected. [ABSTRACT FROM AUTHOR]

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A typical method for measuring the radial thermal conductivity of cylindrical objects is the pipe method. This method introduces a heating wire in combination with standard thermocouples and optical Fiber Bragg grating temperature sensors into the core of a cell. This experimental method can lead to high uncertainties due to the slightly varying setup for each measurement and the non-homogenous structure of the cell. Due to the lack of equipment on the market, researchers have to resort to such experimental methods. To verify the measurement uncertainties and to show the possible range of results, an additional method is introduced. In this second method the cell is disassembled, and the thermal conductivity of each cell component is calculated based on measurements with the laser flash method and differential scanning calorimetry. Those results are used to numerically calculate thermal conductivity and to parameterize a finite element model. With this model, the uncertainties and problems inherent in the pipe method for cylindrical cells were shown. The surprising result was that uncertainties of up to 25% arise, just from incorrect assumption about the sensor position. Furthermore, the change in radial thermal conductivity at different states of charge (SOC) was measured with fully functional cells using the pipe method. [ABSTRACT FROM AUTHOR]

To reliably characterize fast dynamic heat transfer mechanisms, fast-response temperature sensors are crucial, including knowledge about the temporal response. In this paper, the dynamic behavior of a Fiber Bragg Grating temperature sensor is investigated and compared to different types of fast-response thermocouples using two different experimental dynamic characterization methods. A temperature step is generated by either plunging the sensor into a fluid or exposing it to a fluid droplet at different temperatures. The step response is evaluated to determine the sensor response time. Calibration runs are performed for a silica-based 0.125 mm FBG sensor, as well as for 0.16 mm and 0.8 mm exposed tip and 0.25 mm sheathed tip type K thermocouples. Water, glycerin, oil and GaInSn were used to cover a broad range of applications regarding different thermal diffusivities and viscosities. The FBG sensor showed the shortest response times compared to the thermocouples, ranging from 60 ms in oil down to 3 ms in liquid metal, which is 20 % up to 70 % faster compared to a 0.25 mm sheathed tip type K thermocouple. Additional plunging calibration runs of the FBG sensor were performed in a ternary nitrate molten salt mixture (HITEC) to determine its overall and dynamic behavior in corrosive fluids at elevated temperatures. It turns out that the FBG sensor is not affected by the molten salt and shows similar response times to those measured in water. Regarding the characterization methods, both techniques show reproducible results, even though the droplet method is inapplicable for sensors with higher heat capacity or lower thermal conductivity than the calibration fluid. Furthermore, splashing effects for fluids with low viscosity reduce the reliability of the droplet method. The results also show that a dynamic characterization is indispensable for temperature measurements with high temporal resolution because the response time depends on the sensor size and the heat transfer coefficient between sensor and surrounding, which in turn depends on the sensor type, fluid properties and the flow parameters. • FBG sensors are suitable for temperature measurements with high temporal resolution. • Plunging method provides reliable response time measurements in various liquids. • Droplet method is only suitable for specific sensor-liquid-combinations. • Sensor response time strongly depends on application conditions. • FBG sensor provides reliable measurements in molten salts and liquid metals. [ABSTRACT FROM AUTHOR]

• Facilitates advanced Weigh-In-Motion (WIM) techniques for pavement management plan. • Hybrid system with GFRP-FBG sensors with computer vision for WIM measurements. • Addresses wander effect challenge in vehicle weight monitoring. • Provides novel insights into vehicle–road interaction dynamics. The paper addressed the challenges of the two main weigh-in-motion (WIM) systems through a hybrid WIM system, which combines embedded in-pavement sensor systems and computer vision to enhance accuracy while minimizing human intervention. To establish a cost-effective system, this study employed a standard camera integrated with computer vision technique to improve the precision of identifying wheel location and automatically adjust distance calibration, particularly in response to variations in camera angle. In addition, the system achieved real-time vehicle weight detection efficiently by addressing the vehicle wander effect concerns of the in-pavement sensors through camera using computer vision. The system can achieve weight accuracy notably exceeding ASTM 1318E-09 standards, with over 90% accuracy for distances below 0.1 m, demonstrating its potential value in assisting traffic analysis and pavement maintenance by offering real-time, accurate WIM measurements at a low cost for instrumentation. [ABSTRACT FROM AUTHOR]

The construction of steel pipe piles combined with side grouting is regarded as an effective way to improve the uplift bearing capacity of piles for transmission towers in rugged mountainous areas. This new piling technology involves the injection of grout into the annular space between the steel pipe pile and the side boundary of the pre-dug hole, which aims to improve the properties of soil-pile interface. However, to date, there are few studies on the soil-pile interface property and uplift failure model of this new kind of steel pipe piles with side grouting. In this study, the shear properties of the grouting interface between soil and steel plate were investigated, and then compared with the shear tests of undisturbed plastic clay and gravel clayey soil. It is indicated that the shear strength of the grouting interface between soil and steel plate is less than that of corresponding undisturbed soils. In addition, the uplift loading test about two grouted implantation steel pipe piles (GISPP) instrumented with Fiber Bragg Grating (FBG) sensors in plastic clay and gravel clayey soil was carried out, which demonstrates that the failure surface of GISPP mainly occurs in the interface of soil and grouting body. The grouting body can be well bonded to the steel pipe pile after uplift, but the ground surface around the GISPP presents a conical failure model. Finally, a new method considering the conical failure model was proposed to calculate the ultimate uplift capacity of GISPP, which was validated to be efficient and reliable compared with previous calculation methods. [ABSTRACT FROM AUTHOR]

Nowadays, variable preparation, forming and processing methods of fiber metal laminates are constantly developing to meet the requirements of different application fields, hence the characteristics and evolution of residual stresses under different manufacturing conditions deserve more attention. In this work, the evolution behaviors of curing residual stresses in GLARE under a hot-pressing condition were studied, and the residual stress reduction mechanism was also explained. Results suggested the FE prediction models of the entire cure process, verified by the fiber Bragg grating (FBG) sensors, were more precise than the traditional elastic model. Moreover, the stress evolution during the cure process mainly occurred in the cooling stage, in which the different coefficient of thermal expansion (CTE) of aluminum and GFRP played a major role. Meanwhile, curing shrinkage stress in the GFRP layer during the holding stage at curing temperature obviously influenced the final stress level. The residual stresses in GFRP layers differed by 9.6 MPa under a hot-pressing and autoclave condition, in which the convection heat transfer condition played a major role as it caused lower thermal stress in the holding stage and a smaller temperature gradient in the cooling stage. Considering this, a lower cooling rate could be a feasible way to obtain GLARE with lower residual stress under a hot-pressing condition. [ABSTRACT FROM AUTHOR]

The safety and durability of the short suspender, the core bearing member of the middle and lower-bearing concrete-filled steel tube concrete arch bridge, seriously affect the service life of the bridge. In order to better monitor the mechanical performance of the short suspender of arch bridge, two cable force measurement methods, fiber grating sensor method and elastomagnetic sensor method, were adopted to conduct experiment on the cable force measurement of the steel rod type short suspender, with material of 35CrMo, length of 5. 0 m and diameter of 85 mm. The results show that the linear sensing performance and repeatability of the short suspender measured by the two sensors are good, and the cable force measurement error of the fiber Bragg grating sensor is about ±6%. The maximum cable force error of elastomagnetic sensor is 1. 31%, and the measurement error is within ±2%. It is concluded that the two measurement methods won􀆳t be affected by short derrick boundary conditions, such as length, bending rigidity, and are more suitable for arch bridge completed short boom of long-term monitoring. The precision of elastomagnetic sensor completed short boom is more ideal. [ABSTRACT FROM AUTHOR]

This paper demonstrates the fabrication of radiation-resistant fiber Bragg grating (FBG) sensors using infrared femtosecond laser irradiation. FBG sensors were written inside acrylate-coated fluorine-doped single-mode specialty optical fibers. We detected the Bragg resonance at 1542 nm. By controlling the irradiation conditions, we improved the signal strength coming out from the FBG sensors. A significant reduction in the Bragg wavelength shift was detected in the fabricated FBG sensors for a radiation dose up to 105 gray, indicating excellent radiation resistance capabilities. We also characterized the temperature sensitivity of the radiation-resistant FBG sensors and detected outstanding performance. [ABSTRACT FROM AUTHOR]

This study proposed an analytical model to investigate strain transfer mechanism between FBG sensor and measured geogrid. Both geometric and mechanical parameters (bonding length, bonding thickness, bonding width, and Young's modulus) of interaction interface can be taken into account in this model. Both laboratory tensile tests of geogrid and experimental data in published literatures were used to verify the developed model. Validation study shows that the maximum relative error between experimental values and theoretical values is 8.2%, indicating that this theoretical model can be used to reflect geogrid deformation. Parametric study indicates that bonding length, bonding thickness, bonding width, Young's modulus of adhesive layer, and substrate layer have significant influence on strain transfer coefficient. Grey Relational Analysis (GRA) method was used to analyze influencing sensitivity of different parameters. GRA parameter values of bonding width and length are higher than 0.72, indicating that bonding width and bonding length are relatively dominant factors affecting average strain transfer coefficient in comparison with bonding thickness, Young's moduli of substrate and adhesive layers (their related GRA values are all lower than 0.692). • An analytical model to quantitatively evaluate strain transfer between FBG sensor and measured geogrids was proposed. • Influence of different parameters on strain transfer mechanism was quantitatively investigated. • Grey Relational Analysis method was used to analyzed the sensitivity of different parameters. [ABSTRACT FROM AUTHOR]

The standard support vector machine (SVM) performs poorly on the identification problem of low velocity impact areas due to its lower accuracy rate. Improving SVM's performance using the bat algorithm (BA) is feasible, but BA has the premature convergence problem. In this study, a hybrid bat algorithm with double mutation operations (DMBA), in which the Cauchy mutation operator and the extremal optimization mutation operator are integrated into BA, is proposed to enhance BA's ability to jump out of the local optima. Then, a novel SVM based on this hybrid BA, which is called SVM_DMBA, is developed to address the identification problem. Compared with the standard SVM and twelve improved SVM methods which are combined with the standard algorithms, advanced algorithms, and bat variants, the significant performance of SVM_DMBA is validated using UCI datasets. Moreover, to identify low velocity impact areas, SVM_DMBA is applied to the low velocity impact localization system based on fiber Bragg grating (FBG) sensors. The statistical results indicate that SVM_DMBA is a significantly effective method for identifying the low velocity impact areas and generates higher identification accuracy than comparative methods. For 64 low velocity impact areas of 30 mm × 30 mm on an aluminium plate, the average identification error obtained by SVM_DMBA is 1.615%.

The morphing wing trailing edge is an attractive aviation structure due to its shape-adaptive ability, which can effectively improve the aerodynamic performance of an aircraft throughout the whole flight. In this paper, a mechanical solution for a variable camber trailing edge (VCTE) based on a multi-block rotating rib is proposed. Parametric optimizations are conducted to achieve the smooth and continuous deformation of the morphing rib. A prototype is designed according to the optimized results. In addition, the deformations of the trailing edge are monitored via an indirect method using a fiber Bragg grating (FBG) sensor beam. Finally, ground tests are performed to investigate the morphing capacity of the VCTE and the shape monitoring ability of the proposed method. Our results indicate that a maximum deflection range from 5° upward to 15° downward can be obtained for the VCTE and the indirect sensing system can satisfactorily monitor the deformation of the trailing edge.