A template-free alcoholthermal route to Ti(Sn)-doped ZnO nanorods

Ti(Sn)-doped single-crystalline ZnO nanorods with an average diameter of 20 nm and length up to nearly 1 μm were synthesized by a facile ultrasonic irradiation-assisted alcoholthermal method without involving any templates. Photoluminescence spectra of the Ti-doped ZnO nanorods were measured at room temperature and three emitting bands, being a violet emission at 400-415 nm, a blue band at 450-470 nm and a green band at around 550 nm, were detected. The emission intensities of the Ti-doped ZnO nanorods enhance gradually with increasing the doping concentrations. As to the Sn-doped ZnO nanorods, the green emission shifts to 540 nm and the emission intensities increase first but decrease later with increasing the doping concentrations.     

Synthesis and characterization of bismuth doped barium sulphide nanoparticles

We have synthesized BaS:Bi nanocrystalline powder of average grain size 35 nm by solid-state diffusion method using sodium thiosulphate as a flux. During this work we have optimized the nature and amount of flux, amount of the dopant and temperature of firing for maximum yield of photoluminescence. The samples were characterized by X-ray powder diffraction (XRD) method, transmission electron microscopy (TEM), photoluminescence (PL) and UV-visible techniques. On excitation by 425 nm, these nanophosphors give one emission peak at 575 nm which corresponds to green color. In the excitation spectra of these particles there are two peaks at 350 nm and 425 nm. The effect of dopant concentration on the photoluminescence of BaS:Bi nanocrystallites has been studied which is in agreement with the principle of concentration quenching. The energy band gap of bismuth doped BaS nanopowder has been calculated to be 4.25 eV and is blue shifted in comparison to their bulk counterparts. The blue shift may be due to the quantum confinement in the particles.     

Preparation and optical properties of organic/inorganic nanocomposite materials by UV curing process

In this study, photo-polymerized poly(acrylic)/silica hybrid thin films were prepared from various acrylic monomers and monodispersed colloidal silica with the coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MSMA). The silica content in the hybrid thin films varied from 0 to 50 wt.%. The experimental results show that the particle size of silica in hybrid films could be effectively controlled at 15–20 nm as the weight ratio of MSMA to colloidal silica is higher than 0.68 and 0.60 for the poly(methyl methacrylate)/silica (US) and poly(ethylene glycol dimethacrylate-trimethylolpropane trimethacrylate)/silica (UDT) hybrid materials, respectively. The polymerization conversion for US and UDT hybrid materials could reach to 100% and 94.5%, respectively. The comparison of surface roughness with the film thickness is less than 0.10%, indicating the excellent surface planarity of the prepared hybrid thin films. Besides, the prepared hybrid films from the crosslinked acrylic polymer moiety show much better film uniformity, thermal stability and mechanical properties than those obtained from poly(methyl methacrylate). The refractive index decreases with increasing the silica content in the hybrid films. Excellent optical transparency is obtained in the prepared hybrid films. These results show that the prepared hybrid thin films have potential applications as passive films for optical devices.     

Experimentally based strategy for damage analysis of textile-reinforced composites under static loading

For a reliable design of components made of textile composites, a deep knowledge of their failure behaviour and of realistic damage models is necessary. Such models require the onset of damage and the evolution of different damage phenomena to be determined experimentally. In this context, an experimental damage analysis strategy is proposed here that combines crack density measurements, acoustic emission analysis and optical microscopy with the recording of stiffness degradation by ultrasonic wave speed measurements. The correlation between the results of quasi-static tests is discussed for two selected examples of textile composites: multi-layered flat bed weft-knitted glass fibre–epoxy composites and woven glass fibre–polypropylene composites made of hybrid fabrics.     

基于光学小波变换的机器人视觉传感器设计

针对视觉系统处理速度慢的问题,利用光电信息技术设计出基于光学小波变换的机器人视觉传感器。该传感器用4 f光学处理系统实现光学小波变换滤波,以计算机编程加载滤波器,因此兼有光学信息处理的二维、高速、并行和大容量的优点,以及计算机控制灵活的优点。图像特征提取仿真实验结果表明:效果理想,处理速度快,方案可行。     

复合材料层间应变测试实验

复合材料受到应力作用层间会产生变形,应力过大层间会出现撕裂的现象。针对这一问题, 利用光纤法珀应变传感器与复合材料层间间隙尺寸相当的特点,将该传感器置入复合材料层间,在万能拉伸仪上进行复合材料应变测试实验。实验表明:利用光纤法珀应变传感器检测复合材料层间应变的方法是完全可行的。     

一种监控非规整膜系的新方法

由透过率和波长的函数关系可知,膜系中每一层都可能存在若干波长的光信号会出现极值偏转。利用这些波长作为每层膜的监控波长,满足光电极值法的监控条件,由此提出了一种监控非规整膜系的新方法。这些波长可以通过波长搜索的方法而得出。从监控模拟和随机误差曲线可知,该方法继承了光电极值法简单易行以及自动补偿等优点,其反射率在 0.1%范围内变化,与理论曲线基本吻合。     

用打靶法求解双向泵浦的拉曼放大器传输方程

提出了用打靶法计算双向泵浦的拉曼放大器传输方程的算法。该算法不仅可以求解前向泵浦、背向泵浦的拉曼放大器传输方程,也可以计算双向泵浦的拉曼放大器传输方程。该算法利用了先猜测,再修正的逐渐逼近的方法来求解传输方程。利用该算法,对用三波长拉曼光纤激光器泵浦的拉曼放大器进行了优化设计,在波长分别为 1427nm,1445nm 和 1466nm,功率分别为500mW,120mW,400mW 时,获得了 1dB 带宽约为 40nm 的结果,并用试验进行了验证。     

FBG编解码器在W-OCDMA系统中的应用

针对大容量二维组合码,提出一种可调光纤布拉格光栅(FBG)编解码器的设计方法,该设计方法利用了光纤布拉格光栅的反射和可调谐特性,所得编解码器结构简单、容易集成、变址容易。在 OOK调制输出速率为 1Gbit/s,输出功率为 1mW的 W-OCDMA 系统仿真实验中,该 FBG编解码器结构实现了正确的编解码,时间延迟 1ns,功率损耗约 1dB,并且具有良好的匹配滤波特性。该 FBG 编解码器将是适用于 W-OCDMA 系统较为理想的器件。     

Second harmonic generation in self-assembled ZnO microcrystallite thin films

The second-order non-linear susceptibility components were measured using 1.064 μm incident light for ZnO thin films of various thicknesses from 24.4 to 283 nm self-assembled on sapphire substrates by laser molecular beam epitaxy. It was found that the values of the non-linear susceptibility for the films are almost the same as those of bulk material, except the samples with thicknesses ranging from 35 to 64.8 nm, which show a large enhancement effect. For the sample with a thickness of 44.4 nm, the second-order non-linear susceptibility components were found to be approximately 14.7 pm/v for d₃₁, 15.2 pm/v for d₁₅, and −83.7 pm/v, a value approximately 14 times that of the bulk material, for d₃₃. The second-order non-linear coefficient enhancement in the thin films may be resulted from the microcrystallite structures.