scholarly journals A Novel Monitoring Approach for Train Tracking and Incursion Detection in Underground Structures Based on Ultra-Weak FBG Sensing Array

Sensors ◽  
2019 ◽  
Vol 19 (12) ◽  
pp. 2666 ◽  
Author(s):  
Qiuming Nan ◽  
Sheng Li ◽  
Yiqiang Yao ◽  
Zhengying Li ◽  
Honghai Wang ◽  
...  
Keyword(s):  
Safety Management ◽  
High Sensitivity ◽  
Underground Structures ◽  
Long Distance ◽  
Sensing Technology ◽  
Frequency Domains ◽  
Envelope Processing ◽  
Critical Issues ◽  
Vibration Responses ◽  
Subway System

Tracking operating trains and identifying illegal intruders are two important and critical issues in subway safety management. One challenge is to find a reliable methodology that would enable these two needs to be addressed with high sensitivity and spatial resolution over a long-distance range. This paper proposes a novel monitoring approach based on distributed vibration, which is suitable for both train tracking and incursion detection. For an actual subway system, ultra-weak fiber Bragg grating (FBG) sensing technology was applied to collect the distributed vibration responses from moving trains and intruders. The monitoring data from the subway operation stage were directly utilized to evaluate the feasibility of the proposed method for tracking trains. Moreover, a field simulation experiment was performed to validate the possibility of detecting human intrusion. The results showed that the diagonal signal pattern in the distributed vibration response can be used to reveal the location and speed of the moving loads (e.g., train and intruders). Other train parameters, such as length and the number of compartments, can also be obtained from the vibration responses through cross-correlation and envelope processing. Experimental results in the time and frequency domains within the selected intrusion range indicated that the proposed method can distinguish designed intrusion cases in terms of strength and mode.

scholarly journals Combining SDAE Network with Improved DTW Algorithm for Similarity Measure of Ultra-Weak FBG Vibration Responses in Underground Structures

Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2179
Author(s):  
Sheng Li ◽  
Xiang Zuo ◽  
Zhengying Li ◽  
Honghai Wang ◽  
Lizhi Sun
Keyword(s):  
Similarity Measure ◽  
Nearest Neighbor ◽  
Distance Measure ◽  
Integrated Approach ◽  
Structural Vibration ◽  
Distributed Monitoring ◽  
Underground Structures ◽  
Long Distance ◽  
Vibration Responses ◽  
Weak Fbg

Quantifying structural status and locating structural anomalies are critical to tracking and safeguarding the safety of long-distance underground structures. Given the dynamic and distributed monitoring capabilities of an ultra-weak fiber Bragg grating (FBG) array, this paper proposes a method combining the stacked denoising autoencoder (SDAE) network and the improved dynamic time wrapping (DTW) algorithm to quantify the similarity of vibration responses. To obtain the dimensionality reduction features that were conducive to distance measurement, the silhouette coefficient was adopted to evaluate the training efficacy of the SDAE network under different hyperparameter settings. To measure the distance based on the improved DTW algorithm, the one nearest neighbor (1-NN) classifier was utilized to search the best constraint bandwidth. Moreover, the study proposed that the performance of different distance metrics used to quantify similarity can be evaluated through the 1-NN classifier. Based on two one-dimensional time-series datasets from the University of California, Riverside (UCR) archives, the detailed implementation process for similarity measure was illustrated. In terms of feature extraction and distance measure of UCR datasets, the proposed integrated approach of similarity measure showed improved performance over other existing algorithms. Finally, the field-vibration responses of the track bed in the subway detected by the ultra-weak FBG array were collected to determine the similarity characteristics of structural vibration among different monitoring zones. The quantitative results indicated that the proposed method can effectively quantify and distinguish the vibration similarity related to the physical location of structures.

scholarly journals Identification of Ground Intrusion in Underground Structures Based on Distributed Structural Vibration Detected by Ultra-Weak FBG Sensing Technology

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 2160 ◽  
Author(s):  
Weibing Gan ◽  
Sheng Li ◽  
Zhengying Li ◽  
Lizhi Sun
Keyword(s):  
Fiber Optic ◽  
Structural Vibration ◽  
Underground Structures ◽  
Subway Tunnel ◽  
Tunnel Wall ◽  
Sensing Technology ◽  
Detection Approach ◽  
Vibration Responses ◽  
Subway Tunnels ◽  
Weak Fbg

It is challenging for engineers to timely identify illegal ground intrusions in underground systems such as subways. In order to prevent the catastrophic collapse of subway tunnels from intrusion events, this paper investigated the capability of detecting the ground intrusion of underground structures based on dynamic measurement of distributed fiber optic sensing. For an actual subway tunnel monitored by the ultra-weak fiber optic Bragg grating (FBG) sensing fiber with a spatial resolution of five meters, a simulated experiment of the ground intrusion along the selected path was designed and implemented, in which a hydraulic excavator was chosen to exert intrusion perturbations with different strengths and modes at five selected intrusion sites. For each intrusion place, the distributed vibration responses of sensing fibers mounted on the tunnel wall and the track bed were detected to identify the occurrence and characteristics of the intrusion event simulated by the discrete and continuous pulses of the excavator under two loading postures. By checking the on-site records of critical moments in the intrusion process, the proposed detection approach based on distributed structural vibration responses for the ground intrusion can detect the occurrence of intrusion events, locate the intrusion ground area, and distinguish intrusion strength and typical perturbation modes.

scholarly journals Application of Multiscale Fiber Optical Sensing Network Based on Brillouin and Fiber Bragg Grating Sensing Techniques on Concrete Structures

2012 ◽  
Vol 8 (10) ◽  
pp. 310797 ◽  
Author(s):  
Xuefeng Zhao ◽  
Jie Lu ◽  
Ruicong Han ◽  
Xianglong Kong ◽  
Yanhong Wang ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Fiber Bragg Grating ◽  
High Sensitivity ◽  
Bragg Grating ◽  
Accurate Information ◽  
Long Distance ◽  
Fiber Sensing ◽  
Sensing Technology ◽  
Optical Fiber Sensing ◽  
Distributed Optical Fiber

The paper reports the application of the distributed optical fiber sensing technology and the FBG sensing technology in bridge strain monitoring; the overall changeable characteristics of the whole structure can be obtained through the distributed optical fiber sensing technology (BOTDA), meanwhile the accurate information of local important parts of the structure can be obtained through the optical fiber Bragg grating sensor (FBG), which can improve the accuracy of the monitoring. FBG sensor has a high sensitivity, but it can only realize the measurement of local discrete points for the quasidistributed sensing. BOTDA can realize the long distance and distributed measurement, but its spatial resolution is not high. FBG and BOTDA were applied together in bridge monitoring in this test, taking full advantage of the distributed BOTDA on the overall strain measurements of the structure, as well as monitoring the key parts by the arrangement of FBG. The combined application of BOTDA and FBG can achieve the overall monitoring from point to line and then to the surface and, therefore, obtain more comprehensive information on the strain of the test structure.

scholarly journals Nanopore Technology for the Application of Protein Detection

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1942
Author(s):  
Xiaoqing Zeng ◽  
Yang Xiang ◽  
Qianshan Liu ◽  
Liang Wang ◽  
Qianyun Ma ◽  
...  
Keyword(s):  
Single Molecule ◽  
Protein Detection ◽  
High Sensitivity ◽  
Single Molecule Detection ◽  
Sequence Detection ◽  
Fast Detection ◽  
Material Basis ◽  
Sensing Technology ◽  
Detection Technology ◽  
Structure Recognition

Protein is an important component of all the cells and tissues of the human body and is the material basis of life. Its content, sequence, and spatial structure have a great impact on proteomics and human biology. It can reflect the important information of normal or pathophysiological processes and promote the development of new diagnoses and treatment methods. However, the current techniques of proteomics for protein analysis are limited by chemical modifications, large sample sizes, or cumbersome operations. Solving this problem requires overcoming huge challenges. Nanopore single molecule detection technology overcomes this shortcoming. As a new sensing technology, it has the advantages of no labeling, high sensitivity, fast detection speed, real-time monitoring, and simple operation. It is widely used in gene sequencing, detection of peptides and proteins, markers and microorganisms, and other biomolecules and metal ions. Therefore, based on the advantages of novel nanopore single-molecule detection technology, its application to protein sequence detection and structure recognition has also been proposed and developed. In this paper, the application of nanopore single-molecule detection technology in protein detection in recent years is reviewed, and its development prospect is investigated.

scholarly journals Monitoring of a Highly Flexible Aircraft Model Wing Using Time-Expanded Phase-Sensitive OTDR

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3766
Author(s):  
Miguel Soriano-Amat ◽  
David Fragas-Sánchez ◽  
Hugo F. Martins ◽  
David Vallespín-Fontcuberta ◽  
Javier Preciado-Garbayo ◽  
...  
Keyword(s):  
Optical Fibers ◽  
Fuel Efficiency ◽  
Optical Fiber Sensor ◽  
High Sensitivity ◽  
Time Domain Reflectometry ◽  
Structural Deformation ◽  
Flexible Wings ◽  
Sensing Technology ◽  
Distributed Optical Fiber Sensor ◽  
Phase Sensitive

In recent years, the use of highly flexible wings in aerial vehicles (e.g., aircraft or drones) has been attracting increasing interest, as they are lightweight, which can improve fuel-efficiency and distinct flight performances. Continuous wing monitoring can provide valuable information to prevent fatal failures and optimize aircraft control. In this paper, we demonstrate the capabilities of a distributed optical fiber sensor based on time-expanded phase-sensitive optical time-domain reflectometry (TE-ΦOTDR) technology for structural health monitoring of highly flexible wings, including static (i.e., bend and torsion), and dynamic (e.g., vibration) structural deformation. This distributed sensing technology provides a remarkable spatial resolution of 2 cm, with detection and processing bandwidths well under the MHz, arising as a novel, highly efficient monitoring methodology for this kind of structure. Conventional optical fibers were embedded in two highly flexible specimens that represented an aircraft wing, and different bending and twisting movements were detected and quantified with high sensitivity and minimal intrusiveness.

scholarly journals Overview of Anti-Seismic Researches of Underground Structures

2018 ◽  
Vol 38 ◽  
pp. 03038
Author(s):  
Ran Liao
Keyword(s):  
Research Methods ◽  
Underground Structure ◽  
Seismic Damage ◽  
Urban Rail Transit ◽  
Rail Transit ◽  
Underground Structures ◽  
Transit System ◽  
Urban Rail ◽  
Subway System ◽  
Metro System

With the vigorous development of urban rail transit system, especially the construction of subway system, the safety of subway system draws more and more attention. The study of anti-seismic for underground structures has also become an important problem to be solved in the construction of Metro system. Based on the typical underground structure seismic damage phenomenon, this paper summarizes the seismic characteristics, research methods and design methods of underground structures to offer a guide for engineers.

scholarly journals Carbon Allotrope-Based Optical Fibers for Environmental and Biological Sensing: A Review

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2046 ◽  
Author(s):  
Stephanie Hui Kit Yap ◽  
Kok Ken Chan ◽  
Swee Chuan Tjin ◽  
Ken-Tye Yong
Keyword(s):  
Optical Fiber ◽  
Optical Fibers ◽  
High Sensitivity ◽  
Optical Fiber Sensors ◽  
Functional Coating ◽  
Fiber Sensors ◽  
Carbon Allotrope ◽  
Carbon Allotropes ◽  
Sensing Technology ◽  
Wide Range

Recently, carbon allotropes have received tremendous research interest and paved a new avenue for optical fiber sensing technology. Carbon allotropes exhibit unique sensing properties such as large surface to volume ratios, biocompatibility, and they can serve as molecule enrichers. Meanwhile, optical fibers possess a high degree of surface modification versatility that enables the incorporation of carbon allotropes as the functional coating for a wide range of detection tasks. Moreover, the combination of carbon allotropes and optical fibers also yields high sensitivity and specificity to monitor target molecules in the vicinity of the nanocoating surface. In this review, the development of carbon allotropes-based optical fiber sensors is studied. The first section provides an overview of four different types of carbon allotropes, including carbon nanotubes, carbon dots, graphene, and nanodiamonds. The second section discusses the synthesis approaches used to prepare these carbon allotropes, followed by some deposition techniques to functionalize the surface of the optical fiber, and the associated sensing mechanisms. Numerous applications that have benefitted from carbon allotrope-based optical fiber sensors such as temperature, strain, volatile organic compounds and biosensing applications are reviewed and summarized. Finally, a concluding section highlighting the technological deficiencies, challenges, and suggestions to overcome them is presented.

Photodetection Technology Based on Laser Coding Emission

2011 ◽  
Vol 189-193 ◽  
pp. 3745-3749 ◽  
Author(s):  
Jing Guo ◽  
He Zhang ◽  
Xiang Jin Zhang ◽  
Xiao Feng Wang
Keyword(s):  
High Sensitivity ◽  
Avalanche Photodiode ◽  
High Gain ◽  
Low Noise ◽  
High Signal ◽  
Weak Signal ◽  
Echo Signal ◽  
Long Distance ◽  
The Poor ◽  
Theory And Experiment

For the extremely weak echo signal and the poor anti-interference ability of the long-distance laser fuze, the high signal noise ratio (SNR) receiving system based on laser coding mode was designed. In order to improve the weak signal receiving ability, the avalanche photodiode (APD) with high sensitivity, low noise and high gain was adopted. And the optimum multiplication factor of APD when the system obtains the highest SNR was analyzed and calculated. Then, the amplifying circuit optimum matching with APD and the decoding circuit were designed, and validated by the experiments. The theory and experiment results indicate that the design is efficiency and capable to the long distance laser fuze, the system can exactly decode the weak laser coding signals received and export the ignition signal.

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