EPON技术在烟草企业视频监控系统中的应用与研究

EPON(以太网无源光网络)是一种新型的光纤接入技术,其采用点到多点的拓扑结构、无源光传输方式,在以太网基础上承载多业务。EPON网络相对其他光纤接入网来说具有较高性价比,技术比较成熟,能够为终端用户提供可靠的数据、语音和视频业务。本文在描述了EPON网络结构和原理的基础上,探讨了将EPON技术应用于烟草工业企业的视频监控系统中的实践,提出了一种系统结构,为烟草工业企业的安防系统以及生产监控系统建设提出新的思路和建议。     

简单液体CS2多波段非线性光学性质研究

采用双4f相位成像技术,在皮秒时域内分别测量了CS2在532nm和745nm两个波长光学非线性系数的变化。通过数值模拟确定了CS2在这两个波长的光物理参数。实验结果表明,在非共振区内,随着波长的增加,CS2没有双光子吸收,三阶非线性折射率保持不变。     

数字音乐图书馆与计算机光学乐谱识别技术

首先叙述了数字音乐图书馆的基本概念,然后针对数字音乐图书馆实施中面临的大量纸介质乐谱的数字化难题,介绍一种新的乐谱数字化技术———计算机光学乐谱识别技术,并对其实现原理和流程进行了简要阐述。     

分形康托多层结构的光学传输特性

在分形理论的基础上,将分形康托序列引入到一维光子晶体的设计中来,得到了一维准分形康托多层结构,采用传输矩阵法研究了分形康托多层结构的光学传输特性,讨论了该结构的分形维数以及光学传输谱的Scalability和Sequential Splitting特性.这种结构可用于超窄带光子晶体滤波器,在光学精密测量和光通信超密集波分复用等领域中有一定的应用价值.     

Analysis on spectral gain characteristics of PPMgLN based quasi-phase-matching optical parametric amplification

A deep understanding of the spectral gain characteristics of optical parametric oscillators （OPOs） and optical parametric amplifiers （OPAs） is important for a highly efficient optical parametric conversion. We numerically calculated the spectral gain characteristics of a quasi-phase-matching （QPM） parametric conversion process using the periodically poled 6% （mol/mol） MgO doped LiNbO3 （PPMgLN） as the nonlinear crystal. In the simulation we utilized the approach of a transformative matrix of the periodically poled nonlinear medium, which results from the small-signal approximation of three-wave mixed nonlinear equations. Numerical simulation results show that： （1） The full width at half maximum （FWHM） of the spectral gain of the parametric process becomes wider with the increase of parametric wavelength and reaches the maximum at degeneration; （2） The gain coefficient decreases gradually with the increase of parametric wavelength; （3） The spectral gain bandwidth decreases correspondingly with the increase of the nonlinear material length; （4） There exists an optimal parametric wavelength band, which is most suitable for the high gain parametric conversion when pumped by a laser source with a wide wavelength band, such as the high power fiber laser.     

中小型图书馆共享光盘网络的构建与设备的选择

光盘技术的发展及电子资源的日益丰富，推动着我国中、小型图书馆共享光盘物建设进程。本文首先对目前存在的共享光盘网络设备进行了介绍和比较，然后说明了共享光盘资源存储、访问的要求，最后提出了建设一个现代中、小型图书馆共享光盘网络的策略。     

Quantifying and visualizing change: Strain monitoring of tapestries with digital image correlation

A three-year research project at the University of Southampton (2007–2010) investigated whether monitoring techniques commonly used by engineers to assess the strength and durability of materials could be usefully applied to inform the condition assessment of historic tapestries. To date it has not been possible to obtain an objective picture of the overall condition of a tapestry; the study investigated whether it is possible to identify precursors of structural damage. The two techniques, digital image correlation (DIC) and optical fibre sensors, were used to monitor a representative wool fabric, specially woven tapestry samples, a newly woven tapestry, and historic tapestries, both in the laboratory and in situ in a historic house. This study first sets out to answer the question: can DIC be used to monitor and visualize strain in historic tapestries? It is shown that DIC can be used successfully. Secondly, it discusses the map function, a novel development which allowed the monitoring equipment to be moved, so that it could be used in situ in a historic house. Thirdly, it provides further details of the experimental work using optical fibre sensors to confirm the accuracy of the DIC technique.     

正交CaTiO3电子结构及光学性质的第一性原理研究

基于密度泛函理论,采用第一性原理投影缀加波方法(PAW),应用广义梯度近似(GGA)处理交换关联能,计算了正交CaTiO3块体材料的晶格参数、电子能带结构、态密度和光学性质。几何优化结果获得的晶格参数和原子坐标与已有的理论和实验数据很吻合。研究表明,正交CaTiO3是带隙为2.43 eV,价带顶和导带底都在Γ点的直接带隙半导体,价带顶和导带底主要由Ti-3d,O-2p态杂化而成。另外,计算了正交CaTiO3的吸收光谱,发现在波长较短的紫外光波段有一强烈吸收峰,基于能带和态密度分析了吸收光谱与电子跃迁间的关系,为正交CaTiO3的应用提供了理论依据。     

视觉传达设计中的格式塔原理

以格式塔心理学为理论依据,以大量的作品实例,阐释视觉传达设计中的图-底关系、完形原理、错视原理和异质同构原理,对视觉传达设计中图形的结构、张力的形成、及其心理机制进行分析探讨,以提高作品的视觉冲击力和审美效应,并对视觉传达设计运用格式塔原理需要注意的问题做了简要的论述。