光纤法布里-珀罗传感器腔长的傅里叶变换解调原理研究

在宽带光源条件下对光纤法布里-珀罗传感器腔长的傅里叶变换解调原理进行了详细的理论推导,在此基础上给出了具体的实现算法和仿真对比实验.仿真结果表明:采用傅里叶变换可以有效地对光纤法布里-珀罗传感器进行腔长解调.     

中国铅污染的调查研究

阐述了中国铅污染的调查结果,包括:历史回顾、群体铅中毒事件、燃油铅污染、燃煤铅污染、铅中毒率统计和防治研究等6个部分。历史回顾从人类对铅污染危害认识的3次飞跃,反映了铅污染由公共卫生问题上升为人类社会问题;中毒事件调查,告诉人们企业的违规排铅,是铅中毒事件的罪魁祸首;燃油污染调查结果表明,汽油无铅化后,燃油大气铅年排放量比从前平均降低了98%左右;燃煤污染的调查结果表明,中国燃煤铅排放量年均增长9.55%,到2010年,中国燃煤铅排放量突破14 000 t,是汽车尾气铅排放量的35倍,且燃烧大气铅排放量与儿童铅中毒率之间存在显著的正相关关系;中毒率的调查结果表明,2003—2007年中国儿童铅中毒率平均为23.61%,比1994—2003年的35.27%有显著降低,但2007年为23.5%,比2006年的17.2%有所反弹;防治研究指出,中国对铅的研究主要是涉及铅毒理和铅污染防治等方面的研究,2006年发表铅文献量接近1 600篇。防治对策是污染源控制和人群监测,发铅与血铅监测同样可靠。     

金属腐蚀监测的光波导传感方法研究

本文提出一种用于金属腐蚀监测的光波导传感方案 ,用金属膜层局部取代光波导的介质包层 ,构成腐蚀敏感膜 ,从而获取金属腐蚀信息 .依据波导理论选用 72 1比色皿上的石英玻璃作为光波导材料 ,利用电化学方法在波导材料内表面上形成Fe C合金腐蚀敏感膜 ,并用XRD、EDX等对膜层结构进行分析 .在电化学腐蚀膜的同时 ,用光学方法记录光波导输出光功率的变化 ,实验结果表明电化学方法与光学方法获取的腐蚀信息同步 ,证实了所提传感方案可行     

页岩气开采中的若干力学前沿问题

页岩气的开采涉及破裂和收集输运两个关键过程.如何实现2000,m以下、复杂地应力作用下、多相复杂介质组分的页岩层内网状裂纹的形成,同时将孔洞、缝隙中的游离、吸附气体进行高效收集,涉及到诸多的核心力学问题.这一工程过程涵盖了力学前沿研究的诸多领域:介质和裂纹从纳米尺度到千米尺度的空间跨越,游离、吸附气体输运过程中微秒以下的时间尺度事件到历经数年开采的时间尺度跨越,不同尺度上流体固体的相互作用,以及压裂过程中通过监测信息反演内部破坏状态等.针对近年来我们国家页岩气勘探开发工作所取得的成就及后续发展中面临的前沿力学问题,在综合介绍页岩气藏的基本特征和开发技术的基础上,以页岩气开采中的若干力学前沿问题为主线,从页岩力学性质及其表征方法、页岩气藏实验模拟技术、页岩气微观流动机制及流固耦合特征、水力压裂过程数值模拟方法、水力压裂过程微地震监测技术、高效环保的无水压裂技术等6个方面的最新研究进展进行了总结和展望,结合页岩气藏开发的工程实践, 深入探究了其中力学关键问题,以期对从事页岩气领域的开发和研究的从业人员提供理论基础, 同时,该方面的内容对力学学科、尤其是岩土力学领域的科研工作也具有重要指导价值.      

High-sensitivity long-period fiber grating sensor with SAN/cryptophane A for coal mine gas detection

A high-sensitivity long-period fiber grating （LPFG） methane sensor that contains a compact and uniform styrene-acrylonitrile （SAN）/cryptophane A nanofilm is presented. The sensor is prepared by using an automatic dip-coater in a solution of cryptophane A, SAN resin dissolved in ortho-dichlorobenzene, a low- volatile solvent. The effect of film thickness on the LPFG＇s resonant wavelength is thoroughly investigated. The optimum sensor among the three LPFGs with different film thicknesses is directly used to detect the methane concentration in a coal mine gas sample. The results indicate that the sensors with film thicknesses of 484 to 564 nm exhibit a redshifted resonant wavelength when the methane concentration is increased from 0% to 3.5% （vol）. The data demonstrates that the sensor with a film thickness of 484 nm has remarkable sensitivity （~0.633 nm%-X）, and its detection limit can reach 0.2%. The methane concentrations determined by our sensor are consistent with those obtained by gas chromatography.     

KrF准分子激光激发掺锗光纤折射率扰动的非线性过程

本文采用了一种简单的功率监测法,观察了KrF准分子激光对掺锗光纤折射率影响的非线性过程。观察到子纤芯折射率扰动过程中非稳定现象、饱和现象和折射率扰动的非线性。     

光纤光栅多传感器复用的成象光谱技术

本文根据光纤光栅多传感器复用时信号的光谱特征,提出了采用成象光谱技术对复用信号进行解调的方案.文章推导分析了该复用方案的有关参量及特性,并进行了验证实验,获得了与计算结果吻合的实验结果.     

Localization theory of distributed fiber vibration sensor

Based on Sagnac interferometer, a simple distributed optical fiber sensing system with sub-loop is presented to monitor the vibration applied on the sensing fiber. By introducing a sub-loop, three output beams of interference with different delay time are gotten. Location of the vibration is analyzed through mathematical-physical equations. The vibration frequency, amplitude, and location are theoretically simulated. The results agree well with the previous experiments.     

X-ray beam hardening correction for measuring density in linear accelerator industrial computed tomography

Due to X-ray attenuation being approximately proportional to material density,it is possible to measure the inner density through Industrial Computed Tomography（ICT） images accurately. In practice,however,a number of factors including the non-linear effects of beam hardening and diffuse scattered radiation complicate the quantitative measurement of density variations in materials. This paper is based on the linearization method of beam hardening correction,and uses polynomial fitting coecient which is obtained by the curvature of iron polychromatic beam data to fit other materials. Through theoretical deduction,the paper proves that the density measure error is less than 2% if using pre-filters to make the spectrum of linear accelerator range mainly 0.3 MeV to 3 MeV. Experiment had been set up at an ICT system with a 9 MeV electron linear accelerator. The result is satisfactory. This technique makes the beam hardening correction easy and simple,and it is valuable for measuring the ICT density and making use of the CT images to recognize materials.     

石墨烯透明导电薄膜电阻的环境稳定性研究

将石墨烯薄膜置于不同环境气氛中,探究其在不同波长和功率密度可见光辐照下的导电特性.结果表明,石墨烯薄膜在不同条件光照下电阻缓慢上升,光照停止后电阻缓慢下降.氮气环境下石墨烯导电性能最稳定,真空下变化最大,在相同功率密度红光辐照下,样品在氮气、大气和真空下相对电阻变化分别为0.09%、0.22%、0.4%.相同环境下,波长越短,光子能量越大,对样品影响越大,在大气环境下,相同功率密度的蓝光、绿光和红光对样品相对电阻的影响分别为20%、3%、0.22%.