Grating Technology Research Articles

The Martin moving grate technology

The Martin moving grate technology

Ultra-weak FBG sensing for identification and analysis of plastic zone of soil caused by supported excavation

Deformation caused by supported excavation makes significant impact on foundation pit stability. Evaluation of potential plastic zone is crucial for early warning of foundation pit instability. To address the shortcomings of existing evaluation methods, a new identification method based on the ultra-weak fiber Bragg grating (UWFBG) technology was proposed. To validate this approach, a UWFBG monitoring program was implemented in the boreholes as part of the Shanghai Metro Line 18 project. The monitoring results were utilized to determine the range of plastic zone for each borehole. It was noted that there are two plastic deformation zones formed with different mechanisms, one located near the base of the diaphragm wall (DW) and the other is distributed within the range of 6–19 m below the excavation face. Lastly, a criterion of early warning of foundation pit instability was presented. By analyzing the monitoring data, the highest risk level of this project was determined as “Attention”, implying the necessity of taking measures to prevent the local plastic zone from evolving into a full-scale sliding surface.

A deep learning-based method for calculating aircraft wing loads

The purpose of this paper is to propose a novel aircraft wing loads calculation model, called long short-term memory residual network (LSTM-ResNet), which can evaluate the loads based on the strain distribution. To achieve this goal, firstly, the data acquisition experiment is designed and performed with a real aircraft wing. In this experiment, we used the Fiber Bragg Grating (FBG) technology as the measurement method to collect strain-load data from the aircraft wing. Then, we propose the LSTM-ResNet model with the one-dimensional convolutional(1D-CNN) architecture. This model is capable of extracting the temporal and spatial representational information from the strain-load data of the aircraft wing. Experimental results demonstrate that the proposed method effectively evaluate the loads of the aircraft wing. To prove the superiority of LSTM-ResNet model, we compared the proposed model with existing loads calculation methods on our experimental dataset. The results show it has a competitive average relative error (0.08%). Moreover, those promising results may pave the way to use the deep learning algorithm in aircraft wing loads calculation.

Thermal diffusion coupling mechanism and its application of discrete waveguide

For discrete optical systems integrated into optical fibers, the optical fields of the individual waveguides are coupled and correlated with each other. This paper studies how to adjust the refractive index of discrete waveguides by thermal diffusion, so as to enhance the coupling between discrete waveguides, and also constructs the discrete waveguide thermally diffused model and the thermally diffused coupling model of twin-core and three-core fibers. The multicore fiber is heated different times by a hydrogen-oxygen flame, and the outgoing light field at the end face of the optical fiber is monitored at the same time. Then, the three-dimensional refractive index measurement results of the thermally diffused multicore fiber verify the feasibility of thermal diffusion technology to change the refractive index of discrete waveguides for coupling. Thermal diffusion technology can be used to fabricate multicore fiber couplers. By combining multicore fiber and core-by-core inscribed fiber Bragg grating technology and by using thermal diffusion technology, the single-channel sensing measurement can be realized. The method of changing the refractive index of discrete waveguides through thermal diffusion has the advantages of high integration, high stability, and mass fabrication. The research on the thermal diffusion of discrete waveguides can improve the application potential of multicore fiber sensing systems, and promote the broad application of discrete waveguide structure optical fiber in the fields of optical communication, optical sensing, biomedicine, and artificial intelligence.

Ultra-broadband LP01-LP11 mode converter based on superimposed long period grating in PCF

This paper proposes and demonstrates a LP01-LP11 mode converter based on SLPG in PCF. PCF-SLPG is insensitive to temperature and pressure and has a wide wavelength harmonization range, compared with traditional fiber gratings. On the basis of the finite element method and local coupled mode theory, a theoretical model of PCF with SLPG was established and the transmission spectrum of the mode converter was analyzed by simulation. Experimental results show that the conversion efficiency of the PCF-SLPG mode converter is 10 dB approximately and the bandwidth of the 3 dB is about 84 nm, which approaches 1.5 times of the PCF-LPG mode converter. The mode converter is proposed to further expand the bandwidth of PCF-LPG, which lays a theoretical and experimental foundation for the application of PCF gratings technology in optical communication field.

Enhancing FBG Sensing in the Industrial Application by Optimizing the Grating Parameters Based on NSGA-II.

Fiber Bragg grating (FBG) technology has shown a mutation in developing fiber optic-based sensors because of their tiny size, high dielectric strength, distributed sensing, and immunity to high voltage and magnetic field interference. Therefore, FBG sensors significantly improve performance and accuracy in the world of measurements. The reflectivity and bandwidth are the main parameters that can dramatically affect the sensing performance and accuracy. Each industrial application has its requirements regarding the reflectivity and bandwidth of the reflected wavelength. Optimizing such problems with multi-objective functions that might t with each other based on applications' needs is a big challenge. Therefore, this paper presents an optimization method based on the nondominated sorting genetic algorithm II (NSGA-II), aiming at determining the optimum grating parameters to suit applications' needs. To sum up, the optimization process aims to convert industrial applications' requirements, including bandwidth and reflectivity, into the manufacturing setting of FBG sensors, including grating length and modulation refractive index. The method has been implemented using MATLAB and validated with other research work in the literature. Results proved the capability of the new way to determine the optimum grating parameters for fulfilling application requirements.

Waste-to-Energy Generation: Complex Efficiency Analysis of Modern Technologies

Recycling of Municipal Solid Waste (MSW) is a significant challenge all over the world. Waste-to-Energy generation solves the problem of MSW recycling and produces power for urban territories. In this study, the researchers implemented complex economic and ecological efficiency analyses of modern Waste-to-Energy technologies. The fundamental challenge of modern Waste-to-Energy generations is finding the balance between economics, ecology, and productivity. Thus, to assess the effectiveness of various thermal technologies, statistics from enterprises were used. The Balanced Scorecard (BSC) method was implemented to calculate an integral effectiveness of a particular Waste-to-Energy technological approach. Environmental and economic analysess of thermal MSW disposal technologies was carried out by selecting the data from at least 146 functioning plants in Canada, China, Finland, France, Germany, Italy, Japan, the Netherlands, Sweden, and Thailand. The research results confirm that gasification technology was the most promising and the most environmentally and cost effective. Incineration Moving Grate technology was the least effective and attractive Waste-to-Energy technology according to the results of the environmental and economic efficiency assessments. The research results can be used for urban planning in waste recycling projects and the new energy national and municipal agenda. The research results can also be useful for municipal strategic energy and sustainable plans and programs.

Leveraging internal curing effect of fly ash cenosphere for alleviating autogenous shrinkage in 3D printing

• Perforated fly ash cenospheres (PFACs) were used as an internal curing agent for developing printable cement-based materials. • Internal curing effect of PFACs can alleviates autogenous shrinkage strain by 81% in 3D printing component. • Effect of PFACs on the rheology of limestone calcined clay cement (LC3) was evaluated. • Fiber Bragg Grating technology was adopted to study autogenous shrinkage by monitoring the interlayer strain. • Incorporating 15 vol% PFAC to replace sand gives LC3 exceptional resistance to autogenous shrinkage and printability. The development of three-dimensional (3D) printing technology in the construction industry has coincided with growing attention on the investigation of printable cement-based composite. Meanwhile, the exploitation of high-performance and environmentally friendly printable cement-based composite is an inevitable path for the sustainable development of 3D printing in the construction industry. This study proposes the use of perforated fly ash cenospheres (PFACs) as internal curing (IC) agent into limestone calcined clay cement (LC3) mortar to develop a novel green printable cement-based composite. Rheological behavior of LC3 mortar containing PFACs has been shown to meet the requirements of 3D printing. The internal curing effect on autogenous shrinkage of mortar was studied by employing Fiber Bragg Grating (FBG) technology. Compressive and flexural strengths of LC3 mortar containing PFACs were evaluated. Additionally, microstructural investigation was analyzed through SEM, and the hydration products were studied by XRD and TG tests. Results suggest that shrinkage strain of LC3 mortar containing 15% PFAC was approximately 80% lower than that of mortar without PFAC, which indicates that PFAC in LC3 mortar can be effective in holding the mixing water for IC that can reduce the autogenous shrinkage. Furthermore, additional mechanical strength of mortar containing PFAC was generated through IC effect and the pozzolanic activity of PFAC, which can effectively compensate the strength loss caused by the PFAC. However, microstructural investigation indicated that the pozzolanic activity of PFAC has limited effect on cement hydration compared with the introduction of additional IC water. Consequently, this study reveals that it is effective to adopt PFAC as IC agent into LC3 mortar to develop high-performance and sustainable printable cement-based composite.

New shapemeter roll technology based on Fiber Bragg Grating technology for on-line flatness monitoring of thin cold rolled metal sheets

The shape of laminated products is a crucial parameter in high-speed and high-volume finishing lines where they must fulfill tight tolerances. Latent defects are detected by flatness rolls (or shapemeter rolls) inserted in the manufacturing line for online flatness control. A prototype of flatness roll has been developed with high spatial resolution (5 mm) and measurement capability over a thickness range of 0.1–1 mm to evaluate flatness and residual stresses of flat metal strip products manufactured by continuous cold rolling (ultra-thin sheets for packaging and automotive markets). The flatness roll prototype relies on pressure-induced strain sensing on segmented blades using Fiber Bragg Grating technology. Synchronous measurement of the flatness profile across strip width rejects disturbances of strip tension during rolling. We provide a proof-of-concept on pilot lines in both static and dynamic conditions (e.g., roll in rotation and in contact with a strip under tension) and the sensing mechanism shows a capability above 3. This combination of performances remains unique up to now. Interblade crosstalk appears to be an important issue. We propose a crosstalk model that agrees with experimental coupling coefficients. A crosstalk matrix inversion yields the distribution in contact pressure from strain data measured on the reverse side. Additional work will be required to use the flatness roll in industrial conditions.

Twelve-TE mode (de)multiplexer using cascaded subwavelength grating waveguides

This paper presents a low loss, ultra-broadband, and high-order mode (de)multiplexer utilizing subwavelength grating (SWG) technology supporting 12-TE polarized modes (TE0-to-TE11) based on waveguides cascading structure. The proposed device comprises a main SWG bus divided into 6 sections and 11 channel waveguides attached to it through SWG joints. Simulation results obtained using the Rsoft photonics CAD suit show that the designed device has low insertion loss > −1 dB, crosstalk better than − 15 (at the operating wavelength of 1550 nm), ultra-broad bandwidth > 180 nm, and an overall length of 300 µm.

Study of Nonlinear Viscoelastic Mechanical Properties of Degenerated Intervertebral Discs

Biomechanical factors are important factors in inducing intervertebral disc degeneration, in this paper, the nonlinear viscoelastic mechanical properties of degenerated intervertebral discs were analyzed experimentally. Firstly, the loading and unloading curves of intervertebral discs before and after degeneration at different strain rates were compared to analyze the changes of their apparent viscoelastic mechanical properties; The internal stress/strain distribution of the disc before and after degeneration was then tested by combining digital image technology and fiber grating technology. The results show that the intervertebral disc is strain-rate- dependent whether before or after degeneration; The modulus of elasticity and peak stress of the degenerated disc are significantly reduced, with the modulus of elasticity dropping to 50 % of the normal value and the peak stress decreasing by about 55 %; Degeneration will not change the distribution of the overall internal displacement of the intervertebral disc, but has a greater impact on the superficial and middle AF; The stress in the center of the nucleus pulposus decreases, and the stress in the outer AF increases after degeneration. Degeneration has a great impact on the nonlinear viscoelastic mechanical properties of intervertebral disc, which has reference value for the mechanism, treatment and prevention of clinical degenerative diseases.

Smart Manufacturing in Rolling Process Based on Thermal Safety Monitoring by Fiber Optics Sensors Equipping Mill Bearings

The steel rolling process is critical for safety and maintenance because of loading and thermal operating conditions. Machinery condition monitoring (MCM) increases the system’s safety, preventing the risk of fire, failure, and rupture. Equipping the mill bearings with sensors allows monitoring of the system in service and controls the heating of mill components. Fiber optic sensors detect loading condition, vibration, and irregular heating. In several systems, access to machinery is rather limited. Therefore, this paper preliminarily investigates how fiber optics can be effectively embedded within the mill cage to set up a smart manufacturing system. The fiber Bragg gratings (FBG) technology allows embedding sensors inside the pins of backup bearings and performing some prognosis and diagnosis activities. The study starts from the rolling mill layout and defines its accessibility, considering some real industrial cases. Testing of an FBG sensor prototype checks thermal monitoring capability inside a closed cavity, obtained on the surface of either the fixed pin of the backup bearing or the stator surrounding the outer ring. Results encourage the development of the whole prototype of the MCM system to be tested on a real mill cage in full operation.

Adaptive design of dual excitation ultra‐low wavenumber Raman spectroscopy system

AbstractUltra‐low wavenumber or ultra‐low frequency (ULF) Raman spectroscopy using holographic optics is an emerging technique to obtain spectral signatures of chemicals in low energy corresponding to their phases, crystallinity, isomerism, and environmental conditions such as temperature. Commercial turn‐key systems employ mechanical turrets and other such optomechanical moving elements to accommodate multiple laser excitations, which are incident normally on the sample, and the Raman signal is collected in a 180° backscattering configuration. Here, we have developed a system consisting of two single‐longitudinal mode (SLM) lasers and a single‐stage spectrometer. Selected notch filters were based on the volume holographic grating technology providing output beam at a certain angle, which facilitates the possibility of different angles of incidence of the excitation laser on the sample. This adaptive ULF Raman system, therefore, is not only able to acquire high‐quality low‐wavenumber spectral fingerprints of various chemicals but can also be easily reconfigured for differential spectral studies.

Respiratory and heart rate monitoring using an FBG 3D-printed wearable system.

This work proposes a 3D-printed sensor based on fiber Bragg grating (FBG) technology for respiratory rate (RR) and heart rate (HR) monitoring. Each sensor is composed of a single FBG fully encapsulated into a 3D-printable Flexible, during the printing process. Sensors with different material thicknesses and infill densities were tested. The sensor with the best metrological properties was selected and preliminary assessed in terms of capability of monitoring RR and HR on three users. Preliminary results proved that the developed sensor can be a valuable easy-to-fabricate solution, with high reproducibility and high strain sensitivity to chest wall deformations due to breathing and heart beating.

Structure optimization of electrical penetration assemblies: Experimental facts and stress field analysis by the finite element method

Thermal-mechanical induced stress in glass is critical for the performance of glass-to-metal-type electrical penetration assemblies (EPAs) used in nuclear reactors and is mainly determined by the thermal expansion mismatch between glass and metal and the structural design of the EPAs. Here, from the perspective of structural design, a new strategy for optimizing thermal stress in EPA glass is proposed. A flexible structure is designed to act as a stress buffer layer between glass and metal. The stress field of the EPA is analysed in detail using an improved finite element (FE) model, and the fidelity is verified by stress measurements based on fibre Bragg grating (FBG) technology. The results show that the designed buffer structure can effectively reduce the concentration of von Mises stress and tangential stress in glass. Moreover, the effect of the geometric dimension on the stress field of the EPA is limited. In addition, compression tests and thermal shock tests are employed to evaluate the mechanical strength and service performance, respectively. The flexible structure can enhance the mechanical properties and accident-tolerant capability of EPAs. The findings of this study have important technical implications for the optimization of seal configurations in EPAs.

A Wearable System Composed of FBG-Based Soft Sensors for Trunk Compensatory Movements Detection in Post-Stroke Hemiplegic Patients.

In this study, a novel wearable system for the identification of compensatory trunk movements (CTMs) in post-stroke hemiplegic patients is presented. The device is composed of seven soft sensing elements (SSEs) based on fiber Bragg grating (FBG) technology. Each SSE consists of a single FBG encapsulated into a flexible matrix to enhance the sensor’s robustness and improve its compliance with the human body. The FBG’s small size, light weight, multiplexing capability, and biocompatibility make the proposed wearable system suitable for multi-point measurements without any movement restriction. Firstly, its manufacturing process is presented, together with the SSEs’ mechanical characterization to strain. Results of the metrological characterization showed a linear response of each SSE in the operating range. Then, the feasibility assessment of the proposed system is described. In particular, the device’s capability of detecting CTMs was assessed on 10 healthy volunteers and eight hemiplegic patients while performing three tasks which are representative of typical everyday life actions. The wearable system showed good potential in detecting CTMs. This promising result may foster the use of the proposed device on post-stroke patients, aiming at assessing the proper course of the rehabilitation process both in clinical and domestic settings. Moreover, its use may aid in defining tailored strategies to improve post-stoke patients’ motor recovery and quality of life.

Strain Sensor Based on Embedded Fiber Bragg Grating in Thermoplastic Polyurethane Using the 3D Printing Technology for Improved Sensitivity

A new and easy-to-fabricate strain sensor has been developed, based on fiber Bragg grating (FBG) technology embedded into a thermoplastic polyurethane filament using a 3-dimensional (3D) printer. Taking advantage of the flexibility and elastic properties of the thermoplastic polyurethane material, the embedding of the FBG provides durable protection with enhanced flexibility and sensitivity, as compared to the use of a bare FBG. Results of an evaluation of its performance have shown that the FBG sensors embedded in this way can be applied effectively in the measurement of strain, with an average wavelength responsivity of 0.013 5 nm/cm of displacement for tensile strain and −0.014 2 nm/cm for compressive strain, both showing a linearity value of up to 99%. Furthermore, such an embedded FBG-based strain sensor has a sensitivity of ∼1.74 times greater than that of a bare FBG used for strain measurement and is well protected and suitable for in-the-field use. It is also observed that the thermoplastic polyurethane based (TPU-based) FBG strain sensor carries a sensitivity value of ∼2.05 times higher than that of the polylactic acid based (PLA-based) FBG strain sensor proving that TPU material can be made as the material of choice as a “sensing” pad for the FBG.

Development and Application of Fiber-Optic Sensing Technology for Monitoring Soil Moisture Field

Accurate acquisition of the moisture field distribution in in situ soil is of great significance to prevent geological disasters and protect the soil ecological environment. In recent years, rapidly developed fiber-optic sensing technology has shown outstanding advantages, such as distributed measurement, long-distance monitoring, and good durability, which provides a new technical means for soil moisture field monitoring. After several years of technical research, the authors’ group has made a number of new achievements in the development of fiber-optic sensing technology for the soil moisture field, that is, two new fiber-optic sensing technologies for soil moisture content, including the actively heated fiber Bragg grating (AH-FBG) technology and the actively heated distributed temperature sensing (AH-DTS) technology, and a new fiber-optic sensing technology for soil pore gas humidity are developed. This paper systematically summarizes the three fiber-optic sensing technologies for soil moisture field, including sensing principle, sensor development and calibration test. Moreover, the practical application cases of three fiber-optic sensing technologies are introduced. Finally, the development trend of fiber-optic sensing technology for soil moisture field in the future is summarized and prospected.

Stress Monitoring of Roadway with Bolt Sensor Based on Fiber Bragg Grating Technology

Stress Monitoring of Roadway with Bolt Sensor Based on Fiber Bragg Grating Technology

Stress Monitoring of Roadway with Bolt Sensor Based on Fiber Bragg Grating Technology

Stress Monitoring of Roadway with Bolt Sensor Based on Fiber Bragg Grating Technology