基于混沌特性的小波数字水印算法研究

为了提高水印信息的隐藏性和安全性,基于混沌序列的优良特性,本文提出了一种用于图像数字水印嵌入和检测的算法。由于混沌序列对初值具有敏感性,攻击者很难从一段有限长度的序列推断出整个混沌序列的初始条件,因此可保证水印信息的安全性。嵌入水印后的图像具有很好的不可见性,并且对常见的信号处理和噪声干扰具有较好的鲁棒性。     

对小波图像去噪方法的探讨

小波图像去噪方法已广泛应用于图像去噪领域．在对日前小波图像去噪文献进行综合的基础上，描述了信号奇异性，并阐述了三种基于小波阈值去噪的方法，最后对小波去噪方法进行了一些展望．     

Optical encryption with cascaded fractional wavelet transforms

INTRODUCTION Recently, with the development of science andtechnology, more and more people become interestedin researching image encryption techniques. Manymethods have been proposed for optical image en-cryption. Random phase encoding methods and digi-tal holography techniques are effectively used inencrypting (Javidi and Nomura, 2000; Unnikrishnanet al., 2000a; Hennelly and Sheridan, 2003; Nishchalet al., 2004). Meantime some important properties oflight are used to realize encryptio…     

Mathematical methods for modelling price fluctuations of financial times series

Statistical and Fourier analysis methods of time series representing fluctuations of stock market in general and Indian stock markets in particular are well known. This work is motivated by a recent paper by Guharay [Operations Research and Financial Engineering, Princeton University, Princeton, NJ, preprint, 2002] where he has studied trends in the S & P 500 for various time periods using wavelet tools. Our paper deals with a few Indian and Saudi stock prices and return fluctuation for a certain period of time. The main objective of the analysis is to understand the dynamics of the Indian and Saudi stock markets. We look for similarities, point of abrupt changes, normalized data, return, volatility, graph, pure and noise part, correlation lengths, and signal-to-noise ratio.     

东北玉米带热量资源的变化规律研究

应用线性回归、非整数波谱和小波分析等方法,分析了东北玉米主产区热量资源的长期演变趋势和变化周期,并对未来10a的情况进行初步预测。要素包括：日平均气温稳定≥7℃、≥10℃的初、终日期,≥10℃积温和5月∽9月平均气温之和。结果表明,近半个世纪内,≥7℃、≥10℃初日有逐渐提前的趋势,农业生产季内热量资源有增加趋势,但近些年这些要素不稳定。界线温度初、终日存在的23a、15a、和9a左右的变化周期,≥10℃积温和5月∽9月气温之和存在60a、35a∽41a、15a∽16a、9a和3a∽4a变化周期。目前所处的长周期内的暖期很可能在2010年前后结束,积温增加的趋势和农作物播期提前的趋势也将缓解,而且在中短周期内,近几年积温可能将减少,冷害和霜冻可能发生,农作物品种和播期都应有相应调整。     

小波变换在信号奇异性检测中的应用

小波变换突破了传统傅里叶变换等信号处理方法的限制,在时域和频域上可同时对信号实现局部化处理,这更符合信号非平稳的变频带结构特征,因而在信号检测奇异性等方面具有广泛的应用价值。本文简要地介绍了小波应用在信号奇异性检测方面变换的基本原理,并通过仿真实验进行了验证。     

利用第二种间断点对球团矿还原曲线进行缺陷分析

利用第二种间断点对设备故障进行检测已经在机电领域有一定的应用,当机电设施存在一定的故障,其产生的信号也存在突变。文章借助MATLAB软件,用小波变换滤波技术,将球团矿还原检测产生的还原曲线的噪声进行分离,将分离后的高频信号进行分析,可以了解在还原试验过程中,是否有突发因素造成曲线异常等缺陷,达到准确完成球团矿还原性试验的要求。     

Feature extraction related to bearing damage in electric motors by wavelet analysis

The purpose of this paper is to extract features from vibration signals measured from motors subjected to accelerated bearing fluting aging and to detect the effects of bearing fluting at each aging cycle of induction motors. This trending of bearing degradation is achieved by monitoring the changes in the vibration signals at various sub-band levels. This is accomplished by the application of wavelet transforms and multi-resolution analysis in order to extract information from selected frequency bands with minimum signal distortion.     

小波域红外能量图人脸识别中小波基的选取

小波域红外能量图人脸识别技术不但可实现全天候人脸识别,而且能够减少人脸识别中的数据复杂度,但是其识别率和时间花费与小波基的选取有关。为此对几种常用的小波基分别进行了实验,并对实验结果进行了分析和总结。实验结果表明,具有正交性和对称性的小波具有较高的红外人脸识别率。     

基于偏微分方程的常用图像去噪方法比较研究

图像去噪在图像处理中极其重要。本文就几种常用的图像去噪方法进行了详细的综述,阐述了各方法的理论原理以及其优缺点,同时也给出了其对同一副测试图像的去噪效果。