基于四点插值细分小波的SAR图像去噪

针对SAR图像去噪过程中存在降低相干斑与保持有效细节这一矛盾,提出了一种基于四点插值细分小波的SAR图像去噪算法,该方法将小波和细分方法相融合,将四点插值细分规则应用到细分小波中,提出了图像去噪的新方法.该算法先用四点插值细分小波对原始图像进行分解,然后用Bayes自适应阈值及阈值函数对图像进行去噪,最后对去噪的小波系数进行重构,并通过等效视数、边缘保持指数等评价指标对去噪结果进行了评价.实验结果表明,算法的等效视数、边缘保持指数都有所提高,去噪效果得到了优化.     

多小波图像插值算法研究

与单小波变换一样,多小波变换同样具有多分辨分析的特性,1次多小波变换可以将图像分解成4个低频子带和12个高频子带,而且原图像的大小是每个子带的4倍.根据多小波变换的这一特点,利用原图像与经过1次多小波变换后的各高频子带的信息,并考虑各子带的分形维数,提出了一种新颖的灰度图像插值算法.实验结果表明,与传统的插值算法相比,例如双线性插值与双三次多项式插值,该算法的插值效果较好,且克服了单小波插值中出现的斑点干扰.     

加权向量中值滤波器的去马赛克算法

本文在深入研究向量中值滤波器基础上,论述了中值向量和均值向量的关系,提出加权算法设计,改进了向量中值滤波器的算法,实现了有效地去马赛克,本算法具有保护了图像边、提高向量中值插值的效果。     

三维加权PFDK重建算法研究

基于滤波反投影的Feldkamp-Davis-Kress(FDK)算法,具有数学形式简单、容易实现和计算速度快等优点,在医疗和工业等领域得到了广泛的应用.平行重排(PF DK)算法是FDK算法的一种推广,针对PFDK算法重建出的图像受锥角的影响加大的问题,给出一种三维加权PFDK图像重建算法,并研究了重排过程中径向插值间隔对重建图像质量的影响,分别采用三种不同插值总数(插值间隔分别是1单位,0.5单位,0.25单位)重排数据.实验结果表明给出的三维加权PFDK算法可有效减少锥角的影响,且当采用2倍插值总数时重建结果较好.     

基于HSI颜色空间和暗原色先验的去雾算法

为了消除雾天对图像采集的影响,提高图像的质量,解决传统去雾技术对图像信息保留不完整,清晰度不好的问题,文章提出一种转换颜色空间的暗原色先验去雾改进算法.首先将图像的RGB颜色空间转换到HSI颜色空间,然后保持色调分量H不变;对亮度分量I进行暗原色先验去雾,并在进行暗原色去雾时,采用更为精确的四叉树算法求取大气光值;对饱和度分量S进行V变换,低频重构出新的饱和度分量,降低纹理、噪声等信息的影响并提高饱和度.对于含有大片天空区域的图像,则通过进一步提高最小透射率,可以有效地去除图像中的雾和霾,同时还避免了图像出现颜色失真的状况.实验结果证明,与经典的去雾算法相比较,文章算法去雾效果明显,图像清晰度高,图像信息保留比较完整,色彩更加真实自然,且时间复杂度较低.     

双立方插值和二元三次样条插值在心磁图像处理中的应用

心磁图是根据人体心脏跳动产生的微弱磁场测量信号计算得到的医学图像,它较心电图诊断心脏疾病具有更高的灵敏度和准确性.为了提高心磁图的成像精度,通常需要对心磁检测数据进行插值处理.提供了双立方插值和二元三次样条插值两种插值方法,应用实例的结果表明,三次样条插值的效果比双立方插值效果好,基本能达到应用的要求.     

一种新的图像插值算法

在没有先验信息的条件下，本基于图像数据所蕴含的二维空间梯度信息和统计特征，提出了一种新的图像插值算法。这种算法主要包括聚类分析、模式识别和图像插值三个步骤。通过仿真实验，取得了令人满意的结果。     

一种基于脉冲噪声的新型迭代滤波算法

在局部极值噪声检测和迭代中值滤波的基础上,基于图像结构和脉冲噪声的特征分析,有效结合局部极值检测和幅度差阈值、梯度差阈值的检测方法,提出了一种基于噪声检测的迭代脉冲噪声滤除算法.并通过仿真实验和算法评价,验证了该算法不仅能够达到很好的去噪效果,而且在保留图像细节信息方面也取得了一定的成效.     

二元对角向量值有理插值的算法

首先提出了二元对角向量值有理插值问题,它包括主对角和副对角两种向量值有理插值,并分别给出了主对角线和副对角线上向量值有理插值的两种算法,即直接求系数bi,j的算法和基于Samelson广义逆所定义的特殊初等变换的矩阵算法.然后构造了在预给极点情况下求主对角线和副对角线上向量值有理插值的矩阵算法.最后给出多个数值例子说明上述算法的有效性.     

平面图形的几何变换

为了对畸变的图象进行纠正,我们建立了畸变过程的数学模型,并由此推导出了它的逆变换模型,再根据此模型进一步设计了它的算法.算法的核心内容是位置坐标的插值和灰度值的插值.位置坐标的插值用于变换后图象象素点的定位,而灰度值插值用于确定象素点的灰度值.经过这两步插值,便可得到变换后的新图象.本文将给出两种算法,它们在位置坐标的插值方法上有所不同,适用的范围也不同.该方法的主要数学工具是双线性插值.     

基于模糊中值滤波的椒盐噪声去除方法

研究基于模糊中值滤波的椒盐噪声去除方法。通过比较图像各像素点的灰度值,定义基于图像梯度信息的各点被判别为噪声点的模糊隶属函数。利用此模糊隶属函数对中值滤波方法进行加权,得到了一种加权中值滤波器,可实现边缘处椒盐噪声的有效滤除。讨论这种模糊加权方法与其它先进滤波方法的结合途径,指出了其推广应用价值。最后利用数值实验验证本文方法的有效性,结果表明,相比于自适应中值滤波方法,本文方法得到的滤波图像在峰值信噪比及结构相似度方面均有明显提高。     

High‐order partial differential equation de‐noising method for vibration signal

A novel approach for 1D vibration signal de‐noising filter using partial differential equation (PDE) is presented. In particular, the numerical solution of higher‐order PDE is generated, and we show that it enables the amplitude‐frequency characteristic in filter to be estimated more accurately, which results in better de‐noising performance in comparison with the low‐order PDE. The de‐noising tests on different degree of artificial noise are conducted. Experimental tests have been rigorously compared with different de‐noising methods to verify the efficacy of the proposed high‐order PDE filter method. Copyright © 2014 John Wiley & Sons, Ltd.     

WAVELET TECHNIQUE RECOVERING IMAGE BLURRED BY MIXED GAUSSIAN AND SALT-PEPPER NOISE

In this paper, we propose a new method to removing the mixed Gaussian and salt-popper noise based on wavelet. To estimate outlier, A scheme called max-min method is adopted after DWT. Experimental results show that this method is more effective than common image restoration methods, such as Median filter,comter weighted median filter.     

Sinc Sum Function and Its Application on FIR Filter Design

A new function is found and is defined as sinc sum function by the author. It has outstanding properties of stairs shape, global symmetry, local symmetry, derivative formula simplicity, local extreme certainty, oscillation regularity, extreme value stability, etc. These properties are proved. Geometry meaning is explained. As an application of the function, the author has developed a new method to design FIR digital filters with adjustable weights. Filter formula in time domain is the weighted sum of sub-filters. A novel form of frequency response expression is deduced which is the sum of sinc sum functions. One of the remarkable characteristics of the form is that weights of sub-filters can be directly calculated according to the expression. Completing the calculation of the weights means finishing the design of a filter. The weights can be either adjustable or fixed. A method to determine the weights are given. Three examples using the method are selected for the consideration that the new method can be easily compared with some famous window methods. Three new filter formulas are produced. Much better performances can be obtained using these formulas compared with using Hanning window and Blackman window respectively. And the performance designing with the new method is slightly better than that with Hamming window. For fixed weights it is almost as easy as using fixed window to calculate filter coefficients.     

Unscented Kalman filter for time varying spectral analysis of earthquake ground motions

A novel parametric time-domain method for time varying spectral analysis of earthquake ground motions is presented. Based upon time varying autoregressive moving average (ARMA) modeling of earthquake ground motion, unscented Kalman filter (UKF) is used to estimate the time varying ARMA coefficients. Then, time varying spectrum is yielded according to the time varying ARMA coefficients. Analysis of the ground motion record El Centro (1940, N–S) shows that compared to Kalman filter (KF) based method, short-time Fourier transform (STFT) and wavelet transform (WT), UKF based method can more reasonably represent the distribution of the seismic energy in time–frequency plane, which ensures its better ability to track the local properties of earthquake ground motions and to identify the systems with nonlinearity. Analysis of the seismic response of a building during the 1994 Northridge earthquake shows that UKF based method can be potentially a useful tool for structural damage detection and health monitoring. Lastly, it is found that the theoretical frequency resolving power of ARMA models usually neglected in some studies has considerable effect on time varying spectrum and it is one of the key factors for ARMA modeling of earthquake ground motion.     

On the fractional-order extended Kalman filter and its application to chaotic cryptography in noisy environment

In this paper via a novel method of discretized continuous-time Kalman filter, the problem of synchronization and cryptography in fractional-order systems has been investigated in presence of noisy environment for process and output signals. The fractional-order Kalman filter equation, applicable for linear systems, and its extension called the extended Kalman filter, which can be used for nonlinear systems, are derived. The result is utilized for chaos synchronization with the aim of cryptography while the transmitter system is fractional-order, and both the transmitter and transmission channel are noisy. The fractional-order stochastic chaotic Chen system is then presented to apply the proposed method for chaotic signal cryptography. The results show the effectiveness of the proposed method.     

主动约束阻尼开口柱壳的NLMS反馈减振控制

为缩减开口柱壳结构的振动,给出了一种局部主动约束阻尼（ALCD）敷设结构,并结合Lagrange方程和Sanders薄壳理论构建了压电耦合开口柱壳的动力学模型,根据推得的系统状态空间形式,应用归一化最小均方差自适应滤波算法（NLMS）和线性二次规划算法（LQR）设计了一种自适应反馈控制器,通过数值仿真研究了控制参数对开口柱壳中点动态特性和控制电压的影响.结果表明:NLMS反馈控制方法能在不同控制电压频率、滤波阶数和自适应步长下保证对开口柱壳减振的有效性;增加自适应步长和滤波阶数能进一步提高减振控制的响应速率,但会导致控制电压超调量增加,而取较大的滤波阶数和较高频率控制电压可以减小噪声扰动,增加控制系统的可靠性.     

三状态样条滤波与平滑

本基于样条滤波理论，给出了三状态样条滤波与平滑方法。仿真计算与实例数据计算表明，该滤波与平滑方法具有较高的精度和稳定性。     

并行准高斯高阶递归滤波算法研究

三维变分同化系统中一个重要的问题是背景误差协方差矩阵B及其逆的求解.背景误差协方差矩阵的水平变换部分采用递归滤波运算,可以简化矩阵的求解,解决了背景误差协方差矩阵B及其逆难以求解的问题.本文对准高斯高阶递归滤波的算法原理和过程进行了深入研究.因为递归滤波并行的低可扩展性制约了高阶递归滤波算法在三维变分同化系统中的应用,所以本文提出了阶段二维区域剖分并行化方法,实现了并行准高斯高阶递归滤波算法库.数值试验表明,四阶递归滤波1次的效果明显优于一阶4次的滤波效果;并且高阶递归滤波并行算法64核时能达到大约50倍的加速,并行效率高达78%,具有良好的加速效果和较强的可扩展性.