VQ-based digital image watermarking method

A vector-quantisation (VQ)-based watermarking method is presented which utilises the codebook expansion technique. This method is efficient, provides enhanced security and the watermarked image is robust against the effects of VQ compression. Moreover, the watermark extraction can be performed without the original image. Experimental results are presented which demonstrate the effectiveness of this algorithm.     

A NOVEL SPACE-COMPRESSED CHINESE WORD DIGRAM BASED ON BI-CHARACTER CO-ARTICULATION FREQUENCY

Chinese Phonetic-Character Conversion(CPCC) is an important issue in Chinese speech recognition and Chinese sentence keyboard input system. The approaches based on large corpus statistic Markov language model (such as bigram, trigram) become more and more popular today. This paper presents an improved Chinese word bigram, space-compressed Chinese word bigram, which stores the bi-word co-articulation frequency in the form of the bi-character co-articulation frequency. The bi-word co-articulation frequency is estimated from the bi-character co-articulation frequency library. The CPCC experiment with the improved Chinese word bigram shows: it can reach a higher correct conversion ratio with less space occupation.     

GaAs IC CAD及其在通信电路中的应用技术

介绍了自主开发的多个完整实用的 Ga As IC CAD软件 ,包括微波无源元件建模、微波有源器件测试建模、微波毫米波 IC CAD、光电集成电路 CAD、 Ga As VHSIC CAD、微波高速 MCM CAD等 ,并简要介绍了针对 Ga As工艺线的建库工作。以上软件和库已用于多个通信电路的设计。     

智能大厦的通信自动化网络系统

章乎先对智能大厦通信自动化交换网络的组成作了论述;然后主要介绍了ＡＴＭ网络系统的相关技术及其应用。     

基于超混沌系统和密文交错扩散的图像加密新算法

该文提出一种基于超混沌系统优化序列并结合密文交错扩散的并行图像加密策略。首先,对超混沌序列进行改造使得改进序列更适合图像加密;然后,利用改进的混沌序列产生与明文相关的最终密钥序列,使得算法对明文敏感。图像被分成两个子块,以并行方式对子块进行两轮像素加密,并引入密文交错扩散技术。对密钥空间和执行效率、像素分布特性、相关系数、抗差分攻击能力以及密钥敏感性进行了测试和分析,证明了方案的安全性和执行效率。结果表明,该算法安全高效,在图像保密通信中具有较大的应用潜力。     

任意波长间隔的光纤光栅梳状滤波器设计与实现

采样啁啾光纤光栅理论是实现超高信道数梳状滤波器的理想方案,但是一个啁啾模板只能实现特定波长间隔的光梳状滤波器。提出一种利用光纤布拉格光栅(FBG)直流相移实现任意波长间隔梳状滤波器方法。该方法只需一个啁啾模板与亚微米精度的位移台,在灵活性、简单性和制作成本方面有明显优势。仿真和实验表明FBG直流折射率调制可以引入任意的相位偏移。利用该方法实现了波长间隔为100,50,40GHz的梳状滤波器。最后分析了直流相移光栅长度与相位误差对滤波器边带抑制度的影响。     

基于偏振合束的相移雅满剪切干涉仪

相移雅满横向剪切干涉仪非常适合于达到衍射极限的光束的波面检测。为了改进现有的在两路剪切光束中直接插入起偏器的相移雅满剪切干涉仪,提出了一种基于偏振合束的相移雅满剪切干涉仪。该剪切干涉仪利用雅满平板前后表面的反射进行分束并形成两路干涉光束,两路干涉光束分别通过剪切平板后偏振合束并进行偏振移相。它保持了常规雅满剪切干涉仪的光路结构,提高了剪切干涉图的对比度,不再存在插入起偏器引入测量误差的问题。构建了改进前、后的两种相移雅满双剪切干涉仪,并进行了相应的对比实验,实验结果很好地验证了基于偏振合束的相移雅满剪切干涉仪的实用性。     

石墨烯的SiC外延生长及应用(续)

正3.3 X射线光电子能谱XPS能谱分析的基本原理:一定能量的X光照射到样品表面和待测物质发生作用,可以使待测物质原子中的电子脱离原子成为自由电子。通过接收并测量这些光电子的能量,得到原子或分子内部各轨道的结合能,从而就可以了解样品中元素的组成。图8所示为样品的XPS能谱图,图中各峰值     

Electrical characteristics of the ITO/HgInTe photodiodes

Photodiodes designed to be sensitive in the region 0.5–1.7 μm and obtained by vacuum magnetron sputtering of the ITO (SnO₂ + In₂O₃) layer on the surface of the Hg₃In₂Te₆ single crystal are studied. The electrical characteristics, measured at 265–333 K, indicate that the mechanism of charge transport in the diodes under study is thermionic. The current-voltage characteristic and its temperature variations are described quantitatively based on the energy diagram and the found parameters of the heterojunction. Original Russian Text ? L.A. Kosyachenko, I.M. Rarenko, E.F. Sklyarchuk, I.I. German, Sun Weiguo, 2006, published in Fizika i Tekhnika Poluprovodnikov, 2006, Vol. 40, No. 5, pp. 568–571.     

快速热处理对重掺As硅单晶中氧沉淀的影响

对重掺As硅片进行快速热处理，发现重掺As硅片中氧沉淀行为与快速热处理温度、保温时间和降温速度有很大的关系. 随着快速热处理温度的升高、降温速度的增大和保温时间的延长，氧沉淀的密度增大. 最后对影响的机理进行了讨论.