双光栅监测环氧树脂固化过程及玻璃化温度实验

为了实时监测环氧树脂的固化过程,建立了基于 光纤布拉格光栅(FBG)的固化监测系统。将裸FBG、石英毛细管封装FBG和高精度热 电阻浸入到环氧树脂及其固化剂的混合物中,一 起经历固化过 程。在升降温过程中,用热电阻监测环氧树脂内部温度变化,用波长解调仪实时测量两种FB G的波长变化。 实验结果表明,石英毛细管封装FBG监测到的温度变化趋势与热电阻监测结果相同;两种FBG 的波长差反 映了固化过程中的收缩应变,固化初期变化较大,之后逐渐减小。以玻璃态转变温度为分界 点,直接植入 环氧树脂的FBG温度灵敏度分别为石英毛细管封装FBG的5.3倍和为2.2倍。     

应用FBG应变箍传感器的管道安全监测研究

为了对管道的腐蚀以及泄漏进行长期、实时监测, 研发了一种光纤Bragg光栅(FBG)应变箍传感器,利用研发的传感器测量管道的环向应变,通 过环向应变的测量实现管道腐蚀以及泄漏的监测。为了探讨本文方法的可行性,将研发的FB G应变传感器安装在PVC管道上,进行腐蚀与泄漏的模拟实验,实验结果表明,研发的FBG应 变箍传感器可以测量到管道壁厚变化以及泄漏产生的负压波信号。表明用研发的传感器进行 管道腐蚀以及泄漏的方法是可行的。     

拱桥吊杆的光纤光栅监测与健康诊断

对拱桥吊杆内力监测光纤光栅(FBG)传感器的波长与应变和温度的关系进行了理论分析,通过标定试验,得到了FBG应变与温度灵敏系数.在四川峨边大渡河拱桥关键性吊杆中成功布设了FBG应变和温度传感器,提出并实施了现役拱桥吊杆FBG传感器的布设工艺以及布设后吊杆的修复方法.利用布设好的FBG传感器成功监测了车辆荷载下吊杆应变历程和温度变化过程、同一车辆荷载对不同长度吊杆的影响.监测结果表明:FBG传感器能够准确地监测车辆荷载大小和温度变化以其可能存在的损伤.     

FBG嵌入型光纤Sagnac环的窄道空间微流速和温度测量系统

提出了一种光纤布拉格光栅(FBG)嵌入型光纤Sagna c环的窄道空间微流速和温度测量系统,其由传统光纤Sagnac环和嵌入光纤Sagnac环中的FBG 组成。光纤Sagnac环中的保偏光纤(PMF)受到的侧压 力会随着微流体流速的不同而发生变化,通过监测光纤Sagnac输出干涉峰的漂移实现对微 流速的测量。此外,嵌入光纤Sagnac环中的FBG对温度有较高的响应灵敏度,可以实现环 境温度的监测。实 验过程中,用毛细管模拟窄道空间,将光纤Sagnac环中的PMF置于毛细管内部,用 微流泵获得一定范 围的微流速。实验结果表明,当微流体的微流速在0～450μm/min范 围内变化时,光纤Sagnac环输出的干涉谱 向短波方向漂移;由监测波长1522.47544.64nm处的谐振峰可知,测量的微流速平均灵敏 度分别为 5.59pm/(μm/min);实时监测环境温 度的结果表明,在20～45℃范围内,FBG的温 度灵敏度为9.74pm/℃。本文传感器具有测量范围大、灵敏度高、结 构简单和成本低等优点,特别适用于微通道如生物血管等方面。     

FBG应变传感系统在巷道涌水模型试验中的研究

针对传统的电类应变传感器防水性能差、测量精度低和不能满足巷道涌水模型试验的需要等问题,基于模型相似材料研制了一种新型光纤光栅(FBG)应变传感器。采用波分复用(WDM)技术和Fabry-Perot(F-P)腔解调技术组成FBG应变传感网络,并编写了具有实时显示和自动预警功能的系统软件。将该系统用在巷道涌水模型试验中,在巷道周围布置了14个FBG应变传感器,对巷道推进过程以及模型加载和巷道扩挖过程中围岩应变进行实时监测。试验结果表明,设计的FBG应变监测系统测量精度高,防水性能强,并且提前4 206 s成功捕获了巷道涌水前兆信息,为预测煤矿矿等涌水事故提供了一种新的有效手段。     

遥感卫星结构在轨热应变光纤光栅监测方法

遥感卫星结构在轨服役期间易受空间极端温度变化与微重力环境影响容易产生热应变,严重影响探测精度,而现有方法难以实现热应变在轨监测。针对这一问题,提出具有温度解耦功能的热应变光纤光栅监测方法。采用数值模拟方法开展结构热应变计算分析,得到结构整体和局部热加载下温度场和应变场分布特征及变化规律。设计构建热应变光纤监测试验系统,对卫星天线结构模拟试件进行热加载光纤测量试验,测试分析热应变光纤监测精度,验证了方法的有效性。研究结果表明,在?120~120 ℃温度变化范围,利用光纤布拉格光栅传感器和温度解耦方法监测温度和热应变的相对误差分别为1.02%和2.45%;在30~100 ℃局部热加载作用下,结构温度场和应变场的重构误差分别为3.24%和6.61%。该方法在卫星结构在轨监测领域中具有良好的应用价值与前景。     

三向光纤布拉格光栅应变传感器的设计及应变特性

针对多向应变测量问题,采用凸台和圆环状基片结构设计了一种三向光纤布拉格光栅（FBG）应变传感器,实现了对结构三个方向应变的同步测量。通过振动试验台和不锈钢板进行了同电阻应变片的静态对比实验和振动监测实验。结果表明,FBG应变传感器和应变片在三个方向的静态应变曲线基本一致,相关系数分别为0.98、0.98和0.99。振动功率谱分析结果表明,FBG应变传感器和应变片均观察到了一次谐波和二次谐波,频率误差分别为2.77%和0.97%,且应变片还监测到了高次谐波信号。该传感器具有结构简单、尺寸小、测量精度高、定位准确等优点,在多向应变监测领域具有良好的应用前景。     

基于参考光栅的光纤光栅应变传感器温度补偿

为解决光纤布拉格光栅（FBG）应变测量时的应变、温度交叉敏感问题，利用FBG便于构成传感网络的优点，将温度补偿参考FBG与应变测量FBG串联在一路光纤上，根据2只FBG布拉格波长相对漂移获得被测结构应变。双FBG波长相对漂移对温度的灵敏度仅为0．12pm／℃，较好地实现FBG应变测量的温度补偿。参考FBG法原理简单，可操作性强，为FBG应变传感器的实际工程应用奠定了基础。     

基于EFPI和FBG传感器的光纤智能夹层系统研究

以光纤自诊断系统为研究对象,围绕光纤智能夹层(FOSL)制作和标定中的相关理论及技术展开较深入的研究。采用聚酰亚胺薄膜制作了基于非本征法布里-珀罗干涉型(EFPI)传感器和光纤布拉格光栅(FBG)传感器的FOSL。制作过程中,光纤传感器性能完好,FOSL的埋入对复合材料强度影响较小。在此基础上,对FOSL试件中的EFPI和FBG传感器进行了四点弯曲试验。试验表明,FOSL中,EFPI传感器的应变与载荷、FBG波长偏移与应变之间均具有良好的线性关系;在FOSL的制作中,可以选用EFPI和FBG传感器同时监测结构应变和温度。利用FOSL中的光纤传感器网络和先进信息处理技术,可以建立结构损伤主动、在线和实时监测系统。     

光纤光栅传感网络对桥桩结构的健康检测

基于对实验桥墩应变点分布的有限元法分析,设计了相适应的光纤Bragg光栅(FBG)传感网络。传感网络根据土层结构分10层布置,每层包括8个FBG应变传感器和1个温度补偿器。对桥墩进行自平衡静载荷实验,分12次完成,每次加载2350kN并持续2h,FBG传感网络实时监测不同载荷下桥墩桩结构的应变分布。监测结果表明:与传统的载荷-位移(Q-S)曲线方法相比,FBG传感网络在桥墩承载实验中能全程反映整体桩结构的变化,实现对桥梁的健康安全检测。     

Acrylate‐Based Photopolymer for Two‐Photon Microfabrication and Photonic Applications

This paper provides a photopolymerizing material suitable for stereolithography of complex submicrometer‐sized three‐dimensional (3D) structural elements to a broad scientific public. Here, we present the formulation of a polymer (LN1 resin) that allows further research in the field of nanofabrication and ‐technology as it surpasses current material limitations. The polymer consists of multifunctional acrylate oligomers as binder, polyfunctional monomers, and a photoinitiator (PI). The chemistry to form 3D structures is based on photopolymerization of the acrylate system initiated by free‐radical species that are triggered by two‐photon absorption of a PI. Important parameters of photocuring, such as the effects of PI concentration, temperature, and light intensity, were studied using photocalorimetry. The thermal stability of the material was tested using thermal gravimetric analysis, providing key information for electronic and photonic applications. Photonic‐crystal structures generated from this resin exhibiting photonic stop gaps in near‐infrared‐ and telecommunication‐wavelength regions are presented.     

Controlling resist thickness and etch depth for fabrication of 3D structures in electron-beam grayscale lithography

In many applications such as optoelectronic devices, three-dimensional (3D) structures are required. Examples include photonic band gap (PBG) crystals, diffractive optical elements, blazed gratings, MEMS, NEMS, etc. It is known that the performance characteristics of such structures are highly sensitive to their dimensional fidelity. Therefore, it is essential to have a fabrication process by which such 3D structures can be realized with high dimensional accuracy. In this paper, practical methods to control thickness of the remaining resist and etch depth, which may be employed for fabrication of such 3D structures using grayscale electron-beam lithography, are described. Through experiments, explicit control of the remaining resist thickness and etch depth at the resolution of 20 nm for the feature sizes of 0.5 μm and 1 μm has been successfully demonstrated. Also, the 1:1 ratio of silicon to resist etching rates was achieved for transferring the remaining resist profile onto the silicon substrate.     

2D Boron Sheets: Structure,Growth, and Electronic and Thermal Transport Properties

The structures of boron clusters, such as flat clusters and fullerenes, resemble those of carbon. Various two‐dimensional (2D) borophenes have been proposed since the production of graphene. The recent successful fabrication of borophene sheets has prompted extensive researches, and some unique properties are revealed. In this review, the recent theoretical and experimental progress on the structure, growth, and electronic and thermal transport properties of borophene sheets is summarized. The history of prediction of boron sheet structures is introduced. Existing with a mixture of triangle lattice and hexagonal lattice, the structures of boron sheets have peculiar characteristics of polymorphism and show significant dependence on the substrate. Due to the unique structure and complex B? B bonds, borophene sheets have many interesting electronic and thermal transport properties, such as strong nonlinear effect, strong thermal transport anisotropy, high thermal conductance in the ballistic transport and low thermal conductivity in the diffusive transport. The growth mechanism and synthesis of borophene sheets on different metal substrates are also presented. The successful prediction and synthesis will shed light on the exploration of new novel materials. Besides, the outstanding and peculiar properties of borophene make them tempting platform for exploring novel physical phenomena and extensive applications.     

THERMAL RADIATION PROPERTY OF A THREE DIMENSIONAL PHOTONIC CRYSTAL BASED ON MULTIPLE SCATTERING METHOD

We have studied absorption and thermal radiation for a three dimensional lossy photonic crystal of dielectric spheres by using a multiple scattering method. It is shown that such simple structures have excellent selective thermal radiative characteristics in different photonic bands. There is stronger thermal radiation at high frequency than that at low frequency. In comparison with the uniform slab without photonic crystal structure, in the photonic band gap, the thermal emission intensity is greatly suppressed and very weak, but not zero due to the penetration depth. Under the same lattice structure, the thermal emission of photonic crystal varies with the change of the radius of the spheres.     

聚酰亚胺层压工艺的研究

本文首先讨论了聚酰亚胺材料和环氧材料半固化片性能上的差异,并研究了黑氧化、棕氧化对铜表面的形貌和抗剥强度的影响,以及温度、压力、升温速率等层压工艺参数,对聚酰亚胺材料抗剥强度和尺寸稳定性的影响,得出了适合于聚酰亚胺材料的层压工艺。最后,比较了聚酰亚胺层压板和环氧板在耐温性、热冲击、玻璃转化温度等方面的优异性能。     

基于不同器件结构的多指HBT热电稳定性研究

本文基于不同的器件结构同时对多指HBT器件的热稳定性和电稳定性进行了分析和讨论。通过直流测试、热阻计算以及基于S参数的稳定性因子K的计算,评估了两个不同版图结构的HBT器件的热稳定和电稳定特性,实验结果表明高热稳定性的器件具有低电学稳定性。引入一个基于小信号等效电路模型的K稳定因子公式对实验结果进行了合理解释。同时基于该公式,具有热镇流电阻结构的器件稳定性也进行了讨论。     

Behaviors of polymeric materials and their effects on high densityPWB

In this study, properties of some selected, representative high density interconnect (HDI) materials (dielectric and solder mask), including dimensional stability (thermal and chemical), tensile behaviors, and fracture toughness have been investigated. Experimental results show that glass transition temperature of materials cured with the manufacturer recommended schedule did not reach their ultimate, alleged published values, indicating that further curing is needed. Most HDI materials are brittle at room temperature with a low strength and low elongation at failure. It has been found that the resistance to crack propagation of HDI materials is much lower than that of polymer thin films, such as Kapton, widely used in electronic products, it has also been observed that stress-strain behaviors of partially cured materials and fully cured materials are very close at room temperature but very different at higher temperatures. Finite element analyses, however, indicate that low fracture toughness of HDI materials will not be major cause if cracks are observed in the thermal cycling of HDI boards. Rather, it would be due to combined contribution from low strain-at-failure, strong viscoelasticity, and low fracture toughness     

新型掺铒离子氧氟碲酸盐玻璃的光谱性质

探求新的具有优良的热学和光学性能的基质玻璃系统，是获得具有宽带宽和增益平坦的掺Er^3＋光纤放大器（EDFA）的一种有效途径。制备了一种新型氧氟碲酸盐玻璃TeO2-BaF2-LaF3，并对其热学性能和光学性质进行了测试。应用乍得-奥菲尔特（Judd-Ofelt）理论计算了Er^3＋离子的J-O理论参量和荧光寿命r。探讨了氟化物的引入对碲酸盐玻璃结构的改变的影响，并分析了其对玻璃的热学性质和光学性质的影响。实验发现，获得的氧氟碲酸盐玻璃具有优良的热学稳定性（△T=156.6C），宽的荧光半峰全宽（72nm），长的荧光寿命（r=4．9ms）以及良好的平坦增益特性。该玻璃系统有望成为新的宽带光纤放大器用基质玻璃材料。     

刻纹光纤传感器的原理及灵敏度分析

介绍了一种新型的光纤传感器，采用热刻-酸蚀法在光纤上形成一些周期性刻纹结构，使得感受应变量的部分成为光纤本身的固有结构。这种光纤传感器具有线性、可重复的输入、输出响应且没有滞后效应，与其它传感器相比其最大的优点是灵敏度高、外形尺寸小。     

一种高功率白光LED灯具的封装热设计研究

建立了一种大功率白光LED照明灯具的封装结构,采用ANSYS有限元软件对其进行热分析,根据热分析的结果逐步改进封装结构,在考虑成本和尺寸限制的条件下,对LED的封装散热结构进行了优化.