Low Temperature Preparation of Titania Coated PAN Fiber and Its Photocatalytical Property

Titania thin film was deposited successfully on polyacrylonitrile (PAN) fiber by the sol‐gel process with the assistance of tetraethyl silicate (TEOS) at low temperature. It was found that the densification and crystallization of the film was a result of the post‐treatment in boiling water because of the hydrolysis of the Si‐O‐Ti bonds and dissolution of the silica component formed in the film. XRD patterns revealed the existence of anatase phase in the continuous titania layer. The product, titania coated polyacrylonitrile fiber (TiO₂/PAN), showed a high photocatalytic property and good repetition on the photodegradation of methylene blue (MB). The proposed method is expected to be used for the preparation of novel photo‐catalysts based on thermally sensitive substrates.     

1313nm脉冲泵浦下掺Er3+光纤中多波长可见光的产生

本文报道了以1313nmNd:YLF激光脉冲泵浦掺饵(Er³⁺)单模GeO₂/SiO₂光纤而产生多波长可见光的实验,在该光纤中观察到(463～510)nm间的多波长放大自发辐射过程,此过程对应于Er³⁺离子的²G_7/2等几个激发态到⁴I_13/2亚稳态的跃迁.其激发过程是分步的四光子吸收过程,同时,掺饵光纤的红外发射峰1530nm(⁴I_13/2-⁴I_15/2)与1313nm泵浦光之间的三波混频过程也对这一区间的连续多峰的光谱结构有贡献.实验中还观察到540nm附近的绿光辐射.     

Effect of size on the strength of polymeric fibers

Using a molecular model introduced previously, we study the effects of chain-end segregation on the relationship between strength (σ) and diameter (d) in polymeric fibers. For segregated structures with a monodisperse molecular weight distribution, our results show a scaling law σ ～ d^?α, with α in the range [0.4–0.5], in agreement with experimental observation. A weaker dependence is found for polydisperse systems. Further investigation also reveals that macroscopic cracks have little influence on the fiber strength/diameter relationship, unless the crack width shows a faster than linear increase with fiber diameter. Finally, our model results also indicate a very weak dependence of fiber strength on its length, in good agreement with experimental observation. ©1995 John Wiley & Sons, Inc.     

Cytoskeletal involvement in cotton fiber growth and development

The organization of cellulose microfibrils in plant cell walls influences physical properties of the wall and thus cell expansion characteristics. Developing cotton fiber represents an excellent model system for the analysis of the biological regulation of cell wall patterns. Current research indicates that the cytoskeleton has a major role in directing the deposition and organization of cellulose microfibrils in the cell walls of many plant systems, including developing cotton fibers. Both microtubules and microfilaments appear to be involved in regulating changes observed in microfibril patterns during fiber development. The polylamellate architecture of the fiber wall can be attributed to changes in the orientation of cytoplasmic microtubules which appear to direct the orientation of microfibril deposition in each successive layer of the fiber wall. In the drug-induced absence of microtubules, cellulose is deposited in the fiber wall in a swirled pattern of bundled microfibrils. Interaction between adjacent microfibrils may influence cell wall organization on a localized level. In contrast to the direct involvement of microtubules on wall organization, microfilaments appear to be indirectly involved in the deposition of cellulose microfibrils. Current evidence indicates that microfilaments influence wall organization by controlling changes in microtubules patterns. Although a greater understanding of the relationship between the cytoskeleton and the fiber wall is needed, there is sufficient evidence to indicate that genetic manipulation of cytoskeletal components is one path toward future direct manipulation of cell expansion characteristic in many plant systems and may lead to improvements in the textile qualities of cotton fibers.     

单模光纤偏振特性的测试

叙述测量单模光纤偏振特性的基本原理，介绍了单模光纤的偏振度P，位相差δ及保偏光纤的拍长Lp的测量方法。     

光纤连接器

介绍了光纤连接器的结构、端面形状、技术指标要求以及近几年发展起来的新型光纤连接器。对光纤连接器的关键技术———氧化锆陶瓷 (PSZ)插针体的制造进行了详细的分析。结果表明 ,生产陶瓷插针的设备和工艺相对比较复杂 ,一次性的固定投入较多 ,只有达到一定的生产规模才能产生效益     

Efficient second, third, fourth, and fifth harmonic generation of a Yb-doped fiber amplifier

We report generation of the second, third, fourth, and fifth harmonics of the output of a Yb-doped fiber amplifier seeded by a passively Q-switched Nd:YAG microchip laser. We obtained high conversion efficiencies using a simple optical arrangement and critically phase-matched nonlinear crystals. Starting with 320 mW of average power at 1064 nm (86 μJ per pulse at a 3.7 kHz repetition rate), we generated 160 mW at 532 nm, 38 mW at 355 nm, 69 mW at 266 nm, and 18 mW at 213 nm. The experimental results are in excellent agreement with calculations.     

基于道格拉斯格式的宽角有限差分光束传播法分析大角度交叉波导

交叉波导是集成光学中的一种重要的器件单元，针对大角度交叉波导的结构及折射率分布，运用基于广义道格拉斯算子的宽角多步有限差分光束传播法模拟大角度交叉波导的传输特性，数值计算出波导中的光场的分布。与Crank-Nicholson格式的有限差分光束传播法相比，该算法在几乎不增加计算时间和计算机内存资源的情况下，结合了广义道格拉斯格式的有限差分光束传播法截断误差小[只有o(△x)^4]和宽角多步法所具有较高精度的优点，是光波导器件理想的数值模拟工具。在此基础上计算分析了大角度交叉波导的输出分支波导的能量与交叉角度的关系，以及交叉角度对波导间能量耦合的影响。这为实际的设计制作光器件的工作提供了极好的基础。     

An isomorphism theorem for Teichmüller curves

It is proved that for any Fuchsian group Γ such that ℍ/Γ is a hyperbolic Riemann surface, the Teichmüller curve V(Γ) has a unique complex manifold structure so that the natural projection of the Bers fiber space F(Γ) onto V(Γ) is holomorphic with local holomorphic sections. An isomorphism theorem for Teichmüller curves is deduced, which generalizes a classical result that the Teichmüller curve V(Γ) depends only on the type of Γ and not on the orders of the elliptic elements of Γ when ℍ/Γ is a compact hyperbolic Riemann surface.     

A full-field approach for the elastic characterization of anisotropic materials

In the paper a procedure is described whereby the characterization of isotropic and anisotropic laminae is carried out by full-field measurement of the surface rotations under proper flexural loads. The analytic formulation does not necessarily imply a numerical calibration and the elastic constants are determined by integrating the whole experimental data on the surface of the specimen. Measurements were carried out by phase-stepped speckle interferometry using a shearometer based on Michelson design. The experimental instrumentation, including the loading device, and the procedures for the manipulation of experimental data are detailedly described; experimental results obtained on a steel specimen and a composite laminate are also reported.