Exact stationary-wave solutions in the standard model of the Kerr-Nonlinear optical fiber with the Bragg grating

By using dynamical system method to the standard model of the Kerr-Nonlinear optical fiber with the Bragg grating, under fixed parameter conditions, all possible exact parametric representations of the bounded stationary wave solutions are obtained from the double sine-Gordon equation.     

自仿Sierpinski地毯中集合的维数

研究广义Sierpinski地毯的两类子集,它们的编码分别具有线性制约的部分数字频率和水平纤维频率.计算这两类集合的Hausdorff维数,并给出相应的Hausdorff测度为正无穷的充分条件.     

一种碳纤维织物增强复合材料应变率相关的各向异性强度准则

为了获得一种碳纤维二维正交平纹机织布增强树脂基复合材料在一维应变状态下的强度准则,在已完成的准静态和动态压缩实验的基础上,拟合出了单轴压缩下三个主方向上的计及应变率的应力-应变关系式,进而得到初始屈服应力和压缩破坏强度与应变率相关性表达式。依据该表达式,得到了该复合材料在一维应变下考虑应变率效应的Tsai-Hill屈服强度和破坏强度准则方程。通过计算,考察了Tsai-Hill屈服强度和破坏强度准则随应变率的变化规律。结果表明,本文中研究的复合材料的强度性能,不但存在应变率效应,而且这种效应是各向异性的。     

Effects of Viscosity Ratio on Morphological,Rheological and Mechanical Properties of PP/PBT Melt Spun Alloy Fibers

Phase morphology formation plays an important role in the mechanical properties of polymer alloy fibers. The development of the blend morphology depends not only on the intrinsic properties of the component polymers but also on extrinsic factors such as viscosity ratio, λ, in the melt spinning process. The effects of blend component viscosity ratio on the morphological, rheological, and mechanical properties of polypropylene/poly(butylene terephthalate) (PP/PBT) melt spun alloy fibers were investigated. Accordingly, two kinds of PP as matrix phase and two kinds of PBT as dispersed phase, with various melt viscosity, were physically mixed and then blended during the extrusion step of melt spinning. SEM micrographs and rheological and mechanical properties evaluations showed that the morphology of PP/PBT alloy fibers strongly depend on the viscosity ratio, λ. Finer diameter PBT fibrils were observed for Viscosity ratios less than 1 (λ < 1) compared to samples with λ > 1. The best mechanical properties in alloy fiber samples were obtained for the viscosity ratio closest to unity (sample with λ = 0.9). The lowest differences among measured complex viscosities at various shear rates (0.1, 10, and 100 s^?1) were also observed in samples with λ = 0.9. The results showed that the mechanical properties of alloy fiber samples are affected not only by morphological properties observed at different viscosity ratios but also by the properties of the individual polymer components.     

基于Bitaper-LPFG-Bitaper结构的全光纤Mach-Zehnder干涉仪的温度传感特性

提出并制作出一种基于锥体光纤-长周期光纤光栅-锥体光纤结构的全光纤Mach-Zehnder(M-Z)干涉仪传感器,并对其温度传感特性进行了研究.实验结果表明,固定光纤锥体和长周期光纤光栅的结构,仅改变两个光纤锥体之间的距离,对应不同的M-Z干涉谐振峰呈现出不同的温度传感特性:随着两个光纤锥体之间的距离增加,位于短波长处的谐振峰,传感器的温度灵敏度减小,而位于长波长处的谐振峰,传感器的温度灵敏度增加.当传感器长度为16.5 cm时,在1 680 nm附近的温度灵敏度达到0.102 06 nm/℃.实验结果对于锥体光纤-长周期光纤光栅组合型温度传感器的优化设计具有重要参考价值.     

利用低相干光纤动态光散射法测量浓悬浮液中多分散颗粒粒径分布

本文针对高浓度散射介质,用低相干光纤动态光散射技术测量浓悬浮液中多分散颗粒系的粒径及其粒径分布。利用迭代CONTIN算法对实验数据进行反演运算,得到多分散颗粒系的粒径分布结果。结果表明,浓悬浮液中多分散颗粒系的峰值粒径测量值与给定的两种标准粒径值相吻合,其误差在4%之内,粒径分布曲线中各散射颗粒所反映的散射体光强分布与根据Mie散射计算得到的理论值相吻合。实验结果证明低相干光纤动态光散射实验系统能准确测量浓悬浮液中多分散颗粒粒径及粒径分布。     

Study on Phase‐Change Characteristics of PET‐PEG Copolymers

Polyethylene glycol (PEG) was selected as a phase‐change material (PCM) and the phase‐change fibers of its copolymers with polyethylene terephalate (PET), PET‐PEG, were successfully prepared by melt spinning. The PET‐PEG copolymers have solid‐solid phase change characteristics at 10–60°C without obvious liquid substance appearing, while PET/PEG blends will lose their phase‐change characteristics since the PEG of the blends may melt and leak under high temperature. By controlling the molecular weight and relavent proportion of PEG added, the phase‐change temperature range and the enthalpy can be adjusted.     

Thermal Decomposition Behavior of a Heterocyclic Aramid Fiber

Heterocyclic aramid fibers are one of the high-performance fibers with excellent mechanical and thermal properties. In this article, the thermal decomposition behaviors of a type of the fibers were studied in nitrogen and air by pyrolysis/gas chromatography–mass spectrometry (Py/GC-MS), thermal gravimetric analysis–differential thermal analysis/Fourier transform infrared spectroscopy (TGA-DTA/FTIR), and thermal gravimetric analysis–differential thermal analysis/mass spectrometry (TGA-DTA/MS). The results showed that under nitrogen atmosphere, the thermal decomposition mainly happened between 520°C and 580°C, the temperature of the maximum weight loss rate was 550°C, and the weight remaining at 800°C was 58%. HCN, NH₃, NO₂, NO, CO₂, CO, H₂O, and some other compounds containing benzene rings were detected by the TGA-DTA/FTIR. Among these released chemicals, the intensity of the absorption peak assigned to CO₂ was the strongest. These chemicals were also identified by the TGA-DTA/MS. The Py-GC/MS analysis revealed that the number of chromatographic peaks increased with the increase of temperature. Most of the pyrolysis products were produced between 550°C and 600°C, which represented the major pyrolysis process. Moreover, the detection of benzene ring containing compound fragments reflected the process of the molecular chain scission. In air atmosphere, the thermal decomposition mainly happened between 500°C and 680°C. The maximum weight loss rate was observed at 600°C, and almost 100% weight was lost at 900°C. NH₃, NO₂, CO₂, and H₂O were detected by the TGA-DTA/MS, and the ion current intensity of CO₂ was again the strongest with a strong oxidation reaction at around 670°C. It was speculated that the thermal decomposition began with the breaking of the bonds between PPTA (poly-p-phenylene terephthalamide) blocks and heterocyclic blocks at high temperature. Then, with the increase of temperature, the chemical bonds inside the PPTA blocks and heterocyclic blocks were broken. In this process, free radicals that led to restructuring and new breakages to produce micromolecular products were introduced.     

2 kW半导体激光加工光源

针对激光加工在金属材料焊接、熔覆、表面硬化等工业领域的应用,考虑到半导体激光器体积和重量小、效率高、免维护、成本低以及波长较短等特点,设计了功率达2 kW的半导体激光加工光源。在大通道工业水冷条件下,采用48只出射波长分别为808,880,938,976 nm的传导冷却半导体激光阵列作为发光单元,最终研制出了2 218 W高亮度光纤耦合模块。此高亮度模块可以实现柔性加工,直接应用于金属材料焊接、熔覆、表面合金化等工业领域,对于半导体激光器在工业领域的应用具有重要意义。     

新型单模大模场红外硫系玻璃光子晶体光纤设计研究

大模场光子晶体光纤在高功率激光传输、光纤放大器、光纤激光器中的广泛应用, 使其受到研究者的广泛关注.硫系玻璃在红外波段(1–20μm)具有优良透过性能, 且具有折射率高(2.0–3.5)、声子能量低(小于350 cm^-1)、 组分可调等特性, 成为制备红外光纤的理想材料. 本文设计一种基于Ge₂₀Sb₁₅Se₆₅硫系玻璃基质的新型单模传输、低损耗、超大模场面积光子晶体光纤结构, 经理论验证其在λ =10.6 μm处基模限制损耗远低于0.1 dB/m, 高阶限制模损耗大于2 dB/m, 模场面积约为13333 μm². 关键词： 硫系玻璃 大模场面积 红外光子晶体光纤 结构设计