Coating of TiO2 nanoparticles with PbS thin films and preparation of PbS nanoparticles using a one-pot sonochemical reaction under the multibubble sonoluminescence conditions

Preparations of PbS-coated titanium dioxide (TiO₂) and lead sulfide (PbS) nanoparticles under ultrasonic field at the multibubble sonoluminescence (MBSL) conditions were tested in water solutions. Under the optimal MBSL conditions (20 kHz and 220 W power input), PbS nanoparticles (diameter = 40-50 nm) were prepared by treating lead nitrate and thioacetamide for 20 min in water solutions. The size of PbS nanoparticles was found to be easily increased to about 90 nm in diameter by increasing the reactant concentration twice. A similar sonochemical reaction with TiO₂ nanoparticles (about 20-30 nm in diameter) gave rise to PbS-coated TiO₂ nanoparticles with a core/shell structure. The PbS thin film coating was quite uniform and the average coating depth of PbS on the TiO₂ nanoparticles was about 2-3 nm under the described conditions. It is interesting to note that the coating depth was found to be controlled to 2-10 nm range by increasing the amounts of reactants for Pb and S twice with a sonication time of 30 min.     

基于复小波的彩色光流估计

利用色彩恒常性假设,将RGB色彩分量光流基本方程映射至小波域,通过复小波构建的过定线性方程组进行多分辨率光流估计,避免实小波相位震荡带来的光流求解误差,并利用各颜色分量组成的线性方程组的系数矩阵条件数判断求解的可靠性,选择各颜色分量中最可靠的解最为该点最终的光流解。数值实验结果证明了该算法的有效性。     

基于石墨烯的布洛赫表面波调控特性研究

布洛赫表面波(Bloch surface wave,BSW) 具有传输损耗低、显著表面局域场增强、环境敏感等特性,因而被视为研究近场光和物质相互作用的关键技术。其主要在截断的一维光子晶体与外界介质的界面激发并沿此界面传播,通过传播界面微纳结构的设计,可在纳米尺度实现对BSW的有效调控。本文从BSW的模式特性出发,提出了石墨烯加载的一维光子晶体BSW传感器件结构。通过改变石墨烯层的结构参数,调节激发模式在光子带隙中的位置,研究激发模式的光场传输特性,实现对BSW激发波长、振幅和相位的调控。进一步利用其对外界介质折射率变化非常敏感的特性,对其传感检测能力进行研究。结果表明,该器件有望实现高灵敏度的生化传感检测应用。该研究为新型BSW集成光子器件的设计与发展提供了新思路。     

微流控光脉冲调制器

为了解决常见光调制器偏振依赖或结构复杂的问题,本文基于微流控光学提出一种可控光脉冲调制器。利用基于T形结产生的离散液滴和全反射原理的微流控光开关,将连续光变换成数字脉冲信号,并通过调节液滴的长度和生成速率调制光脉冲的宽度和频率。所提微流控光脉冲调制器具有结构简单、插入损耗低、消光比高、易集成的优点。微流控光脉冲调制器的流场与光场特性被分析,结构被优化。研究结果显示：该光脉冲调制器的消光比为17.74 dB,插入损耗为0.49 dB。     

The Role of the Choroid in Stargardt Disease

Stargardt disease is the commonest juvenile macular dystrophy. It is caused by genetic mutations in the ABCA4 gene. Diagnosis is not always straightforward, and various phenocopies exist. Late-onset disease can be misdiagnosed with age-related macular disease. A correct diagnosis is particularly critical because of emergent gene therapies. Stargardt disease is known to affect retinal pigment epithelium and photoreceptors. Many studies have also highlighted the importance of the choroid in the diagnosis, pathophysiology, and progression of the disease. The choroid is in an integral relationship with the retinal pigment epithelium and photoreceptors, and its possible involvement during the disease should be considered. The purpose of this review is to analyze the current diagnostic tools for choroidal evaluation and the extrapolation of useful data for ophthalmologists and researchers studying the disease.     

局部与全局结合的彩色图像序列光流场模型

针对彩色图像序列光流场计算问题并结合现有光流场计算模型,提出3种将局部彩色光流计算模型与全局彩色光流计算模型相结合的混合光流估计模型,从而有效利用局部光流模型计算精度高及全局光流模型可得到致密光流场的优点,并将3种模型进行比较,给出数值实验结果。     

用于空间的三反射镜光学系统设计

现代空间光学的发展需要很大的线视场、像质接近衍射极限或很大相对口径的无中心遮拦反射系统。能满足这些要求的非三反射系统莫属,虽然现在已有功能十分齐全的光学系统自动优化软件,但求出一个合理的初始结构尺寸还是十分重要的。文章主要探讨了用于空间的三反射镜光学系统设计方法。     

基于梯度增强的新闻字幕分割算法

新闻字幕的分割在基于语义的新闻视频检索系统中具有重要的意义,为此提出一种基于梯度增强的新闻字幕分割箅法.该算法使用图像多方向梯度的加权和代替图像的标准方差,通过各方向权值的调节加强某些方向的边缘信息,以提高分割效果.与一些经典的自适应阈值分割算法相比,该算法不仅能够保留大部分笔画,也能有效地减少断笔问题.基于光学文字识别的实验结果证明了文中算法的有效性.     

Set up of a Screen-Printing Procedure for the Production of a β Alumina-Based Gas Sensor*

A gas sensor based on a -alumina thick film was recently developed on a laboratory scale. This sensor can be successfully used for selective detection of CO and NO_x, resulting from an appropriate choice of the working temperature of the sensing element. This paper deals with the approach of the industrial transfer of the sensor prototype, mainly concerning the scale-up of the screen-printing procedure from a hand-operated apparatus to an industrial production machine. Many parameters were already investigated during the laboratory development, namely the ink composition in terms of organic/inorganic component ratio, the type and amount of the liquid dispersant and rheological agent, the composition and softening temperature of the binder, the -alumina/binder weight ratio. During the industrial transfer, some other parameters must be considered, such as the particle size distribution of the ceramic components of the ink, the influence of the mesh number of the screen fabric on the surface texture of the -alumina film, the viscosity performances of the ink as a function of the applied shear rate and ageing. A common commercial metallic paste was also used as reference for optimizing the characteristics of the -alumina based ink.     

基于分布式光纤温度传感器的高压电力电缆温度在线监测系统

根据分布式光纤温度传感器被测信号的特殊性,在常规微弱信号检测的基础上,提出了一种专门的、针对分布式光纤温度传感器系统的微弱信号检测方案,采用软、硬件结合的方案,能够在强噪声下有效地提取微弱信号,以求得尽可能大的信号噪声比,而所需的器件与设备极为通用,相对成本较低,检测整个过程完成的时间也较短,具有较高的实用性。