滑坡光纤神经感测系统:技术与应用

滑坡灾害在我国分布广泛,实施有效的监测预警和风险管理措施是该领域防灾减灾的关键。近几十年来,分布式光纤传感技术(distributed fiber optic sensing,简称DFOS)在滑坡监测领域取得了显著进展,相较于常规监测方法具有分布式、长距离、大量程和多参量监测的优势。首先介绍了几种有代表性的光纤传感技术,提出滑坡光纤神经感测系统的概念,并详细阐述了各类光纤传感器的工作原理及其布设工法。在此基础上,介绍了2个利用超弱反射光纤布拉格光栅(ultra-weak fiber Bragg grating,简称UWFBG)监测技术的典型滑坡案例,并进一步讨论了当前存在的技术瓶颈。案例分析结果表明,光纤神经感测系统能实现远程、实时、高精度的地下多参量数据采集,可准确探测潜在滑面及其他关键界面位置,界面处的多物理量变化为揭示滑坡地下演化过程提供了重要的数据支持,为滑坡预测预警提供了新的思路。

采动覆岩变形多场光纤神经感知与安全保障体系构建研究

地下煤层开采引起煤层上覆岩体的变形、破坏与垮落,若采动覆岩变形破坏监测预警和应急处置不当,往往会导致工作面发生冒顶、突水、瓦斯突出和冲击地压等开采灾害事故。为保障开采工作面的本质安全,需要对煤层采动覆岩变形进行全实时动态感知与全过程智能预警。大量的现场监测试验研究结果表明,煤层上覆岩土体的变形破坏存在不连续和非线性变化特点,因此,如何突破覆岩变形的时空不连续观测瓶颈,实时准确地获取煤层上覆岩土体的多场数据,已成为采动覆岩变形破坏机理研究的关键一环。基于分布式光纤感测技术,对煤层采动过程上覆岩土体的变形场、温度场、渗流场和地电场进行了系统性研究,详细介绍了各物理场的作用机理、观测技术、研究现状以及发展趋势,并分析了基于DAS技术的矿山工程微震研究方向,以期为实现矿山地下空间的“透明化”探测提供理论支撑;通过构建井上井下一体化协同的光纤感知神经网络,建立一套集感知–传输–处理–预警–决策–应急于一体的煤层采动覆岩安全保障体系,该体系由实时感知、可靠传输、智能处理、即时预警和应急决策五大模块构成,可实现采动覆岩变形破坏全过程的动态感知和多场实时数据的关联分析与评价,进而为保障煤层开采全周期安全提供技术支撑,研究成果同时可为开采矿区范围内的地质环境监测评价与修复治理提供参考依据。

边坡多场光纤神经感知与安全保障体系

人类工程活动往往易引发边坡灾害,进而对施工人员安全与工程进度产生重要影响。为获取边坡实时状态信息,基于光电联合监测技术,开展边坡变形、温度、渗流及地电等多场光纤神经感知研究,精准掌握边坡时空连续状态。通过引用物联网、大数据、人工智能等技术,对多场信息进行数据清洗、关联挖掘、聚类分析,挖掘出影响边坡稳定性的控制因素,分析各控制因素的叠加效应,在此基础上建立集异常感知、信息传输、数据处理、决策预警为一体的边坡多场安全保障体系,对边坡潜在风险进行识别、评估及预警,进而作出科学决策并实施应急预案,为保障边坡工程安全与防灾减灾提供参考依据。

Optical Fiber Type Slide Tactile Sensor Used for Underwater Robot

Because of the special underwater environment, many sensors used well in robots working in space or on the land can not be used in the underwater. So an optical fiber type slide tactile sensor is designed by the inner modulation mechanism of the intensity type optical fiber. The principle and structure of the sensor are introduced in detail. The static and dynamic characteristics are analyzed theoretically and experimentally. The dynamic characteristic model is built and the simulation is made by using genetic algorithm based on neural network. In order to use the sensor perfectly, the recognition model of the sensor is built on the basis of the principle of “inverse solution” using neural networks. The control precision and sensitivity of the manipulator are improved.

Structural Damage Assessment by an Embedded Fiberoptic Sensor Array and Its ANN Signal Processor

A novel type of two-dimensional damage assessment system for real time monitoring the structural health of composite structure is described. The configuration of the embedded fiberoptic sensor array and the model of the artificial neural network (ANN) are discussed. The experimental system and results show that the system can monitor a damage of structures with potential application in areas such as space aeronautics, civil engineering, etc.

Artificial Neural Network Model for Optical Fiber Direction Coupler Design

A new approach to the design of the optical fiber direction coupler by using neural network is proposed. To train the artificial neural network,the coupling length is defined as the input sample, and the coupling ratio is defined as the output sample. Compared with the numerical value calculation of the theoretical formula, the error of the neural network model output is 1% less.Then, through the model, to design a broadband or a single wavelength optical fiber direction coupler becomes easy. The method is proved to be reliable, accurate and time saving. So it is promising in the field of both investigation and application.

Novel Fiberoptic Sensing Array and Fundamental Experiments

A suitable fiberoptic sensing array embedded in the smart structure to monitor quasi-distributed forces on the structure is presented in this paper.Artificial nearal networks are used in processing of fiberoptic sensing array signals.Fundamental experiments have been done and the results are also given.

Optical coherence tomography in measuring retinal nerve fiber layer thickness in normal subjects and patients with open-angle glaucoma

Objectives To investigate image characteristics and thickness of the retinal nerve fiber layer (RNFL) in normal and glaucomatous eyes using optical coherence tomography (OCT), and analyze the relationship between RNFL thickness and visual field index.Methods Eighty-three normal persons (150 eyes) and 83 patients with primary open angle glaucoma (POAG, 149 eyes) underwent OCT examinations with 3.4 mm diameter circle scan to calculate the RNFL thickness. Statistical analysis was used to compare differences in RNFL thickness in quadrants and means between the normal and glaucomatous groups and the different stages of POAG. Linear correlation and regression analysis were used to show the correlation between RNFL thickness and visual field index of 115 eyes in glaucomatous patients. Reproducibility, sensitivity and specificity of RNFL measurements using OCT were evaluated.Results RNFL thickness measured by OCT in normal subjects was thicker in superior and inferior, less in temporal, and thinnest in nasal quadrants. The curve showed double peaks. RNFL of glaucomatous patients showed local thinning or defect, diffuse thinning, or both. The mean RNFL thicknesses of the normal group in the temporal, superior, nasal and infeior quadrants were 90.1 ± 10.8 lμm, 140.4 ± 10.5μm, 85.2 ± 14.0 μm, and 140.4 + 9.7 μm, respectively with a mean of 114.2 ± 6.0 μm. The numbers for the glaucomatous group were respectively 56.0 ± 31.0 μm, 81.0 ± 36.3 μm, 47.1 ± 27.5 μm, and 73.4 ±38.4 μm for the four quadrants, with a mean of 64.6 ± 28.8 μm. There was a significant difference in RNFL thickness between the normal and glaucomatous groups (P ＜ 0.000), and the three stages (early,developing and late) of glaucornatous groups (P ＜ 0.000). There was a close negative relationship between RNFL thickness and visual field index ( r = - 0.796, P ＜ 0.0001 ). The sensitivity and specificity of RNFL thickness in POAG measured using OCT were 93.3％ and 92.0％, respectively.Conclusions OCT can quantitatively measure RNFL thickness differences between normal persons and glaucomatous patients. RNFL thickness gradually decreases while visual field defect increases with the development of POAG.

Distributed Discrimination of Strain and Temperature Based on Brillouin Dynamic Grating in an Optical Fiber

This paper reviews distributed discrimination of strain and temperature by use of an optical fiber based on fiber optic nerve systems. The preliminary method based on multiple resonance peaks of the Brillouin gain spectrum in a specially-designed fiber is firstly introduced. The complete discrimination of strain and temperature based on the Brillouin dynamic grating in a polarization maintaining fiber is extensively presented. The basic principle and two experimental schemes of distributed discrimination based on fiber optic nerve systems are demonstrated. The performance of the high discriminative accuracy （0.1 ~C-0.3 ~C and 5 kte-12~te） and high spatial resolution （-10 cm） with the effective measurement points of about 50 for a standard system configuration or about 1000 for a modified one will be highly expected in real industry applications.

Diagnostic value of optic disc retinal nerve fiber layer thickness for diabetic peripheral neuropathy

Objective:To investigate the value of optic disc retinal nerve fiber layer(RNFL)thickness in the diagnosis of diabetic peripheral neuropathy(DPN).Methods:Ninety patients with type 2 diabetes,including 60 patients without DPN(NDPN group)and 30 patients with DPN(DPN group),and 30 healthy participants(normal group)were enrolled.Optical coherence tomography(OCT)was used to measure the four quadrants and the overall average RNFL thickness of the optic disc.The receiver operator characteristic curve was drawn and the area under the curve(AUC)was calculated to evaluate the diagnostic value of RNFL thickness in the optic disc area for DPN.Results:The RNFL thickness of the DPN group was thinner than those of the normal and NDPN groups in the overall average((101.07±12.40)μm vs.(111.07±6.99)μm and(109.25±6.90)μm),superior quadrant((123.00±19.04)μm vs.(138.93±14.16)μm and(134.47±14.34)μm),and inferior quadrant((129.37±17.50)μm vs.(143.60±12.22)μm and(144.48±14.10)μm),and the differences were statistically significant.The diagnostic efficiencies of the overall average,superior quadrant,and inferior quadrant RNFL thicknesses,and a combined index of superior and inferior quadrant RNFL thicknesses were similar,and the AUCs were 0.739(95%confidence interval(CI)0.635–0.826),0.683(95%CI 0.576–0.778),0.755(95%CI 0.652–0.840),and 0.773(95%CI 0.672–0.854),respectively.The diagnostic sensitivity of RNFL thickness in the superior quadrant reached 93.33%.Conclusions:The thickness of the RNFL in the optic disc can be used as a diagnostic method for DPN.