大型工程长期健康监测用FBG应变传感器的研究

为研究适于大型工程长期健康监测的耐久性光纤光栅(FBG)应变传感器,提出并实现了传感光纤无机-聚合物-金属的耐久性组合式封装。对传感元件应变传递的理论计算结果表明,光纤的应变传递机制主要依赖于封装结构的无机内核,金属外套用于工程安装初期对无机内核的保护,聚合物主要起这两者间的连接作用,其应变传递机制被抑制,故即使其力学或材料性能发生转异或劣变,亦不对传感器的耐久性产生显著影响;应变测试的理论分析及模型实验结果均表明,相对于普通聚合物封装的FBG传感器,组合式封装传感器的检测精度有明显提高,验证了理论分析结果的可靠性。     

基于OTDR的油气管道监测及定位方案应用

针对油气管道监测方面的应用,提出一种基于光时域反射仪(OTDR)技术的光缆监测方案,该光缆断缆故障定位告警系统可对油气管道的伴行光缆进行实时监测,并通过对比标准测试曲线和实时测量曲线的差别,自动分析出整条光缆线路是否存在异常,若存在异常则确定异常位置并向监测中心发出短信告警.     

基于OTDR的无源光网络在线监测系统研究

从无源光网络(PON)着手,首先简单介绍了PON的主要特点及其发展现状.在强调了PON网络全光在线监控系统的必要性及重要性后,着重描述了四种基于光时域反射仪(OTDR)的PON全光在线监测系统并分别概括了它们的特性,最后还列举了这四种监测系统的性能对比情况.     

用于光缆线路监测的多通路OTDR模块设计

设计实现了一种多通路OTDR模块,主要由4、8、16和32等数目的子模块组合而成。根据不同的应用场合,用户可自由选配不同的测试波长、动态范围和子模块数量,可工作在备纤/离线/在线等模式,主要用于光缆线路监测领域,具有实时性好、可靠性高和灵活性好等特点。     

Employing the ForWaRD Method to Improve Resolution of Conventional OTDR for Application in SHM

As a fiber sensor,optical time domain reflectometer becomes more and more popular to measure parameters,such as strain and temperature in structural health monitoring(SHM) simultaneously.Since the accuracy of range resolution in optical time domain reflectometer(OTDR) is determined by the pulse width of laser,the range resolution in order of centimeter is achieved by employing of picoseconds lasers which are not commercial.In this paper,to achieve this accuracy with conventional OTDR,Fourier wavelet regular...     

OTDR波形分析及在光纤测量中的应用

根据瑞利散射原理分析了脉冲信号和方波信号的回波波形,并利用数值模拟得到了其理论波形.据此自主搭建了一光纤光时域反射仪(OTDR),对样品光纤进行了实际测量,得到了与理论模拟几乎一致的实测波形.通过对实测波形进行降噪处理得到了高精度的长度测量值(相对误差仅为0.0085%)和损耗测量值(相对误差为0.086%).     

基于无线传感器网络的飞行器结构健康监测系统的关键技术研究与应用

通过建立数据聚合器、时序引擎同步、无线同步信标和温度补偿机制,减小了无线节点之间的时序漂移量;通过利用智能开关、压电悬臂梁结构、电化薄膜可充电电池,从而实现了无线节点的能量收集与储存;通过实施ZigBee协议中所规定的安全服务方法,并且开启基于冲突检测的载波侦听多路存取信道访问方法和采用自适应跳频技术,从而提高了无线通信的安全性与可靠性;通过设置无线节点工作模式的自动调节算法,优化了节点的能效。     

Wireless actuation of piezo-elements for the structural health monitoring of carbon-fiber-reinforced-polymers

The goal of this research is to evaluate wireless actuation of Piezo-Wafer-Active-Sensors (PWAS) to generate Lamb-waves on Carbon-Fiber-Reinforced-Polymers (CFRP). Transmission is done by implementing inductive coupled coils. However, CFRP behaves as an electrical conductor, shielding radio waves with increasing worse effects at higher frequencies. Thus, there is a great interest to evaluate the kilohertz ranges. The actuator node is prepared by combining the PWAS bonded to the surface with an inductive coil and tuning all in resonance by adding passive components. In this way, the actuator receives a windowed-signal at the frequency provided by the coil system. An actuator node is prepared in order to evaluate the power transmission; while three sensors are used to measure the responses from the material. The measurements demonstrate that it is possible to wireless excite Lamb-waves. Finally, preliminary results show the feasibility to determine the presence of structural failure.     

面向楼宇结构健康的光纤传感网络监测系统研究

楼宇健康监测中对主体结构的整体应力场分布及其状态参数分析是在线状态评估技术的瓶颈性问题。为了全面地、连贯地反映建筑物的整体状态信息,搭建了一种面向建筑物主体结构的光纤传感网络,提出了一种将结构中应力场信息与整体位置偏移数据相对应的映射算法。算法根据材料力学和挠度理论将弯度矩阵用于应力场与位移场的换算。仿真分析了主结构体中水平梁与垂直梁在受到外部载荷时,其应力场的分布规律,从而为传感单元的铺设提供了量化依据。实验采用方形钢与工形钢模拟主结构,加载外部应力范围为200~1000 N,传感单元选用光纤光栅应变传感器,并采用同类型温度传感器进行温漂补偿。测试结果显示,水平梁与垂直梁的交叉位置处最敏感,波长偏移总量约25 nm,梯度距离0.5 m处波长偏移总量为16 nm,波长偏移量可以很好地反映应力场分布。根据波长偏移数据解算的主体结构位置偏移量平均误差7.46%和6.34%。方形钢和工型钢对应的应力与位置偏移量的平均比率分别为1.99×10?7 m和2.79×10?7 m。可见,该系统可以测试计算结构体的整体健康状态。     

On Development of MySignals based prototype for application in health vitals monitoring

Wireless Personal Communications - India's health infrastructure is under pressure since the daily COVID-19 cases have crossed the milestone of 4 Lakhs cases per day which surpass the previous...     

新型光时域反射计在无源光网络中的应用

提出并实验验证了一种利用自主研制的OTDR来有效定位PON的支路断点或异常损耗事件的方法,讨论了在PON的测量中OTDR面临的新问题和新要求.     

Resolution enhancement in time domain reflectometry systems

The resolution enhancement of time domain images obtained from electromagnetic and acoustic TDR systems is reported.     

The long pulse effect in FEL's

The paper, by means of Green's function and Fourier spectral theory, investigates spontaneous radiation of a single pulse electron bean in free electron lasers with a helically periodical magnetic field. It is found that there are fast and slow electroagnetic waves as well as normal in the interaction region, and that the energy spectrum of spontaneous emission is not only dependent on the imposed helical field, but also modulated sensitively by the electron beam pulse. Under some conditions, the spectrum may have main peaks more than one, showing oscillations, that is, the long pulse effect.     

A fault-tolerant structural health monitoring protocol using wireless sensor networks

In wireless sensor network-based event detection approaches, when the decision is taken based on the measurements of sensors, sensor-fault and noise-related measurement error should be taken into account. Using Bayesian approach to form a judgment is problematic without additional information or assumptions (for example, the difficulty of knowing prior probabilities in practice). In making the final decision using the majority decision rule (as well as the k-out-of-n rule), measurement of every sensor is considered as fully reliable. However, due to sensor fault and environmental noise, the preciseness of all measurements may not be guaranteed in real-life applications. This paper presents a Dempster–Shafer theory of evidence-based structural health monitoring protocol using wireless sensor networks that overcome these limitations. Our proposal effectively discounts the unreliable observer’s (sensor’s) measurements. Extensive simulations show significant improvement in terms of detection accuracy as compared to other well-known approaches.     

Exploitation of the ambient noise for the structural health monitoring of bars and tubes

Image processing is a very vast field that includes both IT and applied mathematics. It is a discipline that studies the improvement and transformations of digital images hence permitting the improvement of the quality of these images and the extraction of information. The comparison of digital images is a paramount issue that has been discussed in several researches because of its various applications especially in the field of control and surveillance such as the Structural Health Monitoring using acoustic waves. In this study we will present an experimental study conducted on a bar and a tube in order to show the constant possibility of performing a structural health monitoring in a medium by studying the ambient noise present therein. Finally, a comparison algorithm described in a previous work (Hourany et al. in Leban Sci J 17(2):177–192, 2016) will be validated in order to show the influence of the presence of a defect in the structure on the cross-correlation.     

Method for PMD vector monitoring in picosecond pulse transmissionsystems

A method and a device are proposed that allow measurement of the polarization mode dispersion (PMD) in a transmission line without data traffic interruption. The PMD vector information is extracted from the optical data signal spectrum. The method is experimentally verified by measuring of first-order PMD     

机电设备运行状态健康监测系统应用研究

随着我国科学技术的进步与发展,企业中机电设备逐渐向高精度、多功能的方向发展,对于机电设备运行过程中的健康监测问题始终受到人们关注.本文通过了解机电设备相关故障机理,阐述了健康监测系统的主要功能,通过实例分析,充分的证明了监测系统在使用中的优越性,存在一定的生产价值及推广价值.     

THE LONG PULSE EFFECT IN FREE ELECTRON LASERS

The spontaneous radiation from a single pulse electron beam in Free Electron Lasers is dealt withby solving one-dimensional wave equations.The obtained results show that there is the long pulse effect aswell as the well-known short pulse effect.     

High efficiency long pulse FIR Raman conversion in ammonia

Generally the quantum efficiency of FIR Raman generation in molecular gases is below the theoretical value. This disagreement is particularly evident in Raman scattering from pulsed sources with short pulse length, when the vibrational saturation limits the power conversion. Other nonlinear processes can overcome this saturation, but they require a very intense pump power for too short a time to use the FIR radiation in high sensitive experiments with heterodyne detection. This is the case, for instance, of RFWM. In this work we describe the experimental conditions to achieve a high efficiency 90 micron Raman conversion in ammonia, with both short and long pulses.     

大能量长脉冲激光能量计吸收体温度特性

以大能量长脉冲激光能量的准确测量需求为牵引,针对激光能量计吸收体温度特性进行了数值分析研究。结果表明:吸收体内壁温度随脉冲结构呈周期性振荡,随着壁深的增加,震荡幅度迅速地降低,吸收体外壁温度周期性消失。单脉冲能量相同时,脉宽越短,吸收体内壁温升越高;重复频率越高,吸收体内壁温升越高。而总能量相同时,重复频率越高,内壁温升越低。通过对吸收体结构的优化设计,不仅能够获得序列长脉冲激光的总能量,而且可以获得低重频（一般不大于10 Hz）序列脉冲激光的每个脉冲能量,从而为长脉冲激光能量计的设计及应用等提供参考依据。