基于SVD、DCT和RSA加密数字水印算法研究

提出了一种基于SVD、DCT、RSA加密数字水印算法,该方法是将载体文档图像做8＊8块的DCT变换,水印图像进行了Arnold处理,将水印图像嵌入到变换的SVD正定矩阵中,修改中频域频谱系数,同时对文档使用RSA算法进行加密,含有水印的图像经IDCT变换存成嵌入水印的图像。通过提取变换域的SVD,提取数字水印,经过RSA算法加密后解密该文档,在经过猫脸逆变换处理得到数字水印图像,水印图像的提取IDCT实验结果表明,本文算法具有安全性高、鲁棒性强以及嵌入水印较好的视觉隐蔽特性、算法处理速度快等特点。     

Accurate mirror-based camera pose estimation with explicit geometric meanings

An accurate closed form solution is proposed to estimate camera pose by several mirrored reference object images acquired via a planar mirror under different unknown poses. Compared with state-of-the-art methods, our method is more accurate when there are more than three images and has explicit geometric meanings. This method also properly handles cases in which some of the mirror poses are parallel. The central idea is to minimize an error metric based on all reflections of rotation, which enables the camera rotation to be estimated directly by SVD of sum of mirrored camera rotations. After that, the camera translation is computed by solving a large system of linear equations to minimize object space collinearity error. Both synthesized data and real data experiments show the advantages of our approach.     

基于SVD的双线性非负矩阵集分解

非负矩阵分解（non-negative matrix factorization,NMF）是一种常用的非负多元数据描述方法。处理数据矩阵集时,NMF描述力不强、推广性差。基于双线性型的非负矩阵集分解（bilinear form-based non-negative matrix set factorization,BFBNMSF）是对NMF的扩展,处理数据矩阵集时,BFBNMSF比NMF描述力强、推广性好。但BFBNMSF在初始化时使用随机分布,为使BFBNMSF更快收敛,该文提出一种基于奇异值分解（Singular value decomposition,SVD）初始化的BFBNMSF,即SVD-BFBNMSF,对系数矩阵进行初始化,已达到快速收敛的目的。实验结果表明：与传统BFBNMSF比较,该方法在收敛速度确有所改善。     

一种用于密码协议形式化验证的简单逻辑

给出了一个可用于密码协议形式化验证与设计的简单逻辑.该逻辑采用抽象的通道概念表示具有多种安全特性的通信链路,可在比现有认证逻辑的更抽象的层次上对协议进行处理.     

MIMO Systems in Random Uncorrelated,Correlated and Deterministic Radio Channels

The paper discusses the BER and spectral efficiency of different MIMO systems in random uncorrelated, correlated and deterministic environments, and more specifically uncorrelated and correlated Rayleigh and Ricean fading channels. It is known that the so-called MIMO eigenmode transmission assumes channel knowledge at the transmitter for pre-coding, whereas V-BLAST and STC do not assume the channel knowledge at the transmitter, instead they use it at the receiver for recovering the transmitted information. It is shown that for the same spectral efficiency, the BER performance of the MIMO eigenmode transmission outperforms MIMO systems like V-BLAST and STBC. In fully correlated random environment, transmitting through the largest eigenmode exploits the full transmitter-receiver array gain and diversity order, giving the maximal possible performance in terms of reducing the BER. In any of the scenarios, transmitting through the largest eigenmode gives better performance in terms of reducing the BER compared with STBC systems. Spatial multiplexing through the so-called eigensets (sets which consist of transmission modes with significant channel gain) outperforms systems like V-BLAST. In this context, adaptive modulation has been used to minimize the overall BER for a given spectral efficiency.     

Monitoring of black tea fermentation process using electronic nose

Black tea fermentation is essentially an oxidation process. After the plucked tea leaves are treated by series of processes called withering (removal of moisture by air flow), pre-conditioning and CTC (essentially maceration and cutting of leaves), the leaves are subjected to the process of fermentation by exposing them to air by laying the cut tea leaves on floor, trough or moving conveyor under controlled temperature, humidity and air-flow conditions. During this process, the leaves change colour from green to coppery brown and the grassy smell gets transformed to floral smell. It is critical that the leaves be allowed to ferment only up to the desired limit and both under and over fermentation result in deteriorated quality of black tea. Out of the two detectable parameters (colour and smell), smell is very important since a strong, very specific fragrance emanates from the leaves once leaves are optimally fermented. A new electronic nose-based approach for monitoring of tea aroma during fermentation is proposed. Two methods namely the 2-Norm method (2NM) and the Mahalanobis distance method (MDM) were tested and the results were correlated with the results of colorimetric tests and human expert evaluation.     

一种低复杂度LMMSE信道估计算法

针对传统线性最小均方误差(LMMSE)信道估计器矩阵求逆运算复杂度大的问题,提出了一种以相关带宽为准则提取信道自相关矩阵主要信息的子阵分块算法.根据信道相关带宽所计算的分块尺度将信道自相关矩阵分割为若干子块,包括非重叠分块法和重叠分块法.运算求逆过程中仅利用表征信道主要信息量的低频对角子阵,而忽略其他表征信道高频信息的子阵,可有效降低LMMSE算法中大的自相关信道矩阵求逆运算所带来的复杂度.该算法在频率选择性慢衰落信道下,与LMMSE和低秩估计算法进行了相关性能及运算复杂度对比分析,结果表明,该算法能以较微弱的性能代价换取系统复杂度的明显降低.