一种基于分块DCT变换和水印置乱的嵌入算法

本文提出一种以图像为水印的DCT变换的数字水印算法,为实现数字水印的嵌入后原始图像不会出现块效应,首先我们对水印图像进行了置乱,为使分块后每块水印图像能完整的嵌入到原图像每块的直流和低频分量部分,我们对水印和原始图像分别进行了4×4和8×8分块DCT变换,为了增加水印嵌入的鲁棒性,我们把水印的每个子块都同时嵌入到多个原图像的子块中。试验结果证明该算法具有较好的不可见性,鲁棒性和抗攻击性。     

基于m序列采样性质的并行扰码方法

为了解决目前SDH通信中并行拢码方法存在的不足，提出了一种新的并行扰码方法。将并行扰码处理过程归结为对m序列的采样过程。当采样间隔为2的幂次时，m序列的采样子序列与原序列具有相同的生成多项式，只是起始状态不同。利用这一性质，并行扰码处理器可分解为数个并行位宽更小的并行扰码器，从而提高了运行速率。该处理器结构简单，不占用硬件寄存器资源，能更好地满足高速传输系统中的时序要求。用FPGA实现了该方法并在实际中得到了验证。     

中国教育电视台的卫星远程教育传输平台

论述了中国教育电视台远程教育传输平台前端系统的基本结构,并着重从MPEG-2应用的角度分析了其中的"数字电视编码系统"和"再复用系统",并指出利用此传输平台可开发出更多的广播电视和远程教育应用.     

基于复合混沌的自适应图像加密算法

复合混沌迭代系统保持了所有迭代子系统的混沌特性，比单个子系统的动力学行为复杂得多，其生成的密钥串按二进制位独立同分布。为了更好地进行图像加密，提出了一种基于复合混沌的自适应图像加密算法。该算法是利用密钥串的值，结合图像像素值确定的置乱顺序对图像进行加密。实验表明，用该算法可以达到很好的自适应加密效果。当总密钥长度大于128bits时，该系统是很难破解的。     

Social dominance in preschool classrooms.

The authors examined preschoolers' aggressive and cooperative behaviors and their associations with social dominance. First and as predicted, directly observed aggressive interactions decreased across the school year, and same-sex aggression occurred more frequently than cross-sex aggression. Next, the authors examined the relation between aggression and reconciliation, cooperation, and social display variables. Teacher ratings of children's aggression related to observed aggression but not to observed "wins" of aggressive bouts. Instead, wins were related to cooperation and display variables. Finally, they examined the relative power of wins and cooperation in predicting 2 measures of social dominance. After age was controlled, wins alone predicted teacher-rated social dominance. Results are discussed in terms of different forms of competition and how school ethos affects these forms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

中国海外留学人员和"海归派"的状况调研报告

八十一万留学生中归国创业者近二十万人,“留学热”和“回国潮”是当代人才流动的一道风景线。上海十一位首席科学家青一色是“海归派”人士。在全球人才争夺战中,我国海外留学生成了发达国家猎取的目标。留在海外的近千名“尖子人才”、五万多名“优秀人才”和数量可观的“特殊人才”有待于我们吸引、招聘和充分利用。     

基于混沌加密的彩色图像盲数字水印算法

针对单一混沌加密算法安全性较差的问题,提出一种基于扰动的二维混沌加密算法,利用二维Chebyshev映射和m-序列扰动作为混沌发生器,用于加密水印图像.将彩色载体图像绿色分量进行3级小波变换,提取其低频部分作为嵌入区域.将加密后的水印嵌入绿色分量的低频部分.实验结果表明,该算法计算速度较快,可以抵抗JPEG压缩、噪声、...     

STM-1解扰系统的并行化技术研究与ASIC设计

依据ITU-TG.707/Y.1322建议中给出的串行扰码算法推导出并行扰码算法,并由此算法设计出SDH8路并行扰码/解扰器。采用FPGA对该设计加以验证,证明设计方案是可行的。在此基础上,采用ASIC设计方法设计实现了STM-1解扰系统。     

Low-Temperature Growing Anatase TiO2/SnO2 Multi-dimensional Heterojunctions at MXene Conductive Network for High-Efficient Perovskite Solar Cells

A multi-dimensional conductive heterojunction structure,composited by TiO2,SnO2,and Ti3C2TX MXene,is facilely designed and applied as electron transport layer in efficient and stable planar perovskite solar cells.Based on an oxygen vacancy scramble effect,the zero-dimensional anatase TiO2 quantum dots,surrounding on two-dimensional conductive Ti3C2TX sheets,are in situ rooted on three-dimensional SnO2 nanoparticles,constructing nanoscale TiO2/SnO2 heterojunctions.The fabrication is implemented in a controlled lowtemperature anneal method in air and then in N2 atmospheres.With the optimal MXene content,the optical property,the crystallinity of perovskite layer,and internal interfaces are all facilitated,contributing more amount of carrier with effective and rapid transferring in device.The champion power conversion efficiency of resultant perovskite solar cells achieves 19.14%,yet that of counterpart is just 16.83%.In addition,it can also maintain almost 85%of its initial performance for more than 45 days in 30–40%humidity air;comparatively,the counterpart declines to just below 75%of its initial performance.     

一种DCT变换域的鲁棒数字水印

提出一种以二值图像为水印的离散余弦变换(DCT)域数字水印算法,对水印图像进行Arnold置乱,用置乱次数作为提取时的密钥,将置乱后的水印图像和载体图像分别进行分块DCT。为了使嵌入的水印具有较强的鲁棒性,把水印的每个子块同时嵌入到多个载体图像的子块中,按照奇数块和偶数块分别将水印嵌入到直流分量和交流分量的中频系数中,实现水印的完全嵌入。实验结果证明,该算法具有良好的鲁棒性和不可见性,能够抵抗有损压缩、剪切、随机涂改和白噪声等攻击。