Estimation of 1/f noise

Several models have emerged for describing 1/f^γ noise processes. Based on these, various techniques for estimating the properties of such processes have been developed. This paper provides theoretical analysis of a new wavelet-based approach which has the advantages of having low computational complexity and being able to handle the case where the 1/f^γ noise might be embedded in a further white-noise process. However, the analysis conducted here shows that these advantages are balanced by the fact that the wavelet-based scheme is only consistent for spectral exponents γ in the range γ∈(0, 1). This is in contradiction to the results suggested in previous empirical studies. When γ∈(0, 1) this paper also establishes that wavelet-based maximum-likelihood methods are asymptotically Gaussian and efficient. Finally, the asymptotic rate of mean-square convergence of the parameter estimates is established and is shown to slow as γ approaches one. Combined with a survey of non-wavelet-based methods, these new results give a perspective on the various tradeoffs to be considered when modeling and estimating 1/f^γ noise processes     

Detection of known signals in 1/f fractal noise

Based on the whitening property of wavelet transformation for 1/f noise, this paper addresses the problem of detecting deterministic signals in the presence of 1/f fractal noise. The transfer function of whitening filter is provided as well as the condition for whitening. The receiver structure based on Karhunen-Loeve expansion and the decision rule are also given. Finally performance of the detector is analyzed.     

基于曲线拟合的SINS/GPS紧密组合导航系统

在工程实际应用中,由于GPS、北斗等卫星导航系统的卫星信号传输、导航计算等均需要耗费一定的时间,当用户接收机输出导航信息时已经产生了延时。尤其对于高动态用户,这一输出延时现象将会导致严重的位置误差和速度误差。针对此,提出了基于曲线拟合的SINS/GPS紧密组合导航系统,解决了高动态时GPS延时问题对导航系统的影响,从而通过曲线拟合的方法保证了时间同步的精度。最后对改进后的系统进行了仿真验证,结果表明该系统的水平位置精度、速度精度均得到显著提高,验证了该方法的有效性。     

基于DM6437的压缩感知1/f噪声估计

基于压缩感知及稀疏分解的数据估计,将采集到的含高斯白噪声的1/f噪声数据信号传输至数字信号处理器TMS320DM6437系统,利用其自带小波函数进行小波分解稀疏化,通过压缩感知重构估计1/f分型信号,并尝试改变迭代次数优化估计效果,计算参数γ值并输出。仿真表明,DM6437系统可以很好地利用压缩感知及稀疏分解技术估计出1/f分型信号,大大优化了硬件检测1/f噪声的方法。     

基于多尺度Wiener滤波器的分形噪声滤波

针对淹没在1/f噪声中的有用信号恢复问题,本文提出了一套基于双正交小波变换与Wiener滤波的多尺度滤波算法,并设计出多尺度Wiener滤波器.首先,利用双正交小波变换将带有1/f噪声的信号分解成多尺度的子带信号,通过小波变换对1/f噪声的白化作用,消除了1/f噪声的非平稳性、自相似性和长程相关性.其次,在小波域内,利用Wiener滤波,实现了噪声和有用信号的分离,估计出了各子带中的有用信号.最后,利用双正交小波的精确重构性,较好地恢复出淹没在1/f噪声中的有用信号.仿真实验表明,该滤波器能有效的抑制分形噪声,显著地提高信噪比.     

Modelling 1-D signals using Hermite basis functions

The paper discusses a method for estimating the Hermite coefficients of a discrete-time one-dimensional signal. To estimate the Hermite coefficients a solution based on Gaussian quadratures is used. The paper also looks at various least mean squared (LMS) estimation methods to estimate two further parameters which are incorporated into the orthonormal Hermite basis function; a spread term and a shift term. In addition, the effects of scaling, dilation and translates of a signal on its Hermite coefficients, spread and shift terms are presented. The paper concludes with a brief discussion on the potential application of the Hermite parameters as features for use in problems requiring shape discrimination within a one-dimensional signal. It also mentions those applications where this was found to be appropriate     

基于曲线拟合的投弃式剖面仪电感量算法

本文研究的结果,为深海走航投弃式剖面仪在大深度测量的信道分析过程中电感量的计算提供了一种可行的计算方法,对于深海投弃式剖面仪信道分析的研究具有一定的意义.     

Model for the excitation of 1/f noise by high-frequency a.c. signals

A model is presented for the excitation of 1/f noise in carbon and semiconductor resistors by high-frequency a.c. signals. The model does not require special theories on 1/f noise; the observed 1/f noise is attributed, as usual, to resistance fluctuations.     

船体外板曲线曲面拟合研究

在船体外板的制造业中,由于各种船体的外表面大都是由复杂的不可展空间曲面构成,把钢板加工成符合船体制造的外板曲面非常复杂。在此基于NURBS样条曲面的特点,采用NURBS三次样条插值函数方法,经过对曲线曲面拟合方法建立相应的船体外板型值表,以某船厂船体外板为例,通过Auto CAD软件,进行了曲线、曲面的拟合,得到了符合船板制造的拟合外板曲面。     

基于曲线拟合的棋盘角点提取算法

由于环境及相机拍摄效果的影响,导致对棋盘格进行角点提取时出现许多错误和冗余的角点,为此提出了一种基于曲线拟合的棋盘角点提取算法。该算法是在Harris角点检测算法的基础上,将多项式曲线拟合应用到提取的结果中,更加精确地提取出亚像素角点,实验结果表明该算法是有效可行的。     

一种高效的基于曲线拟合的虹膜区域分割方法

虹膜识别由于一系列优于其它生物特征识别方法越来越受到欢迎。虹膜识别系统的高可靠性正是得益于其独特的、不变纹理虹膜区域。根据大量的研究表明,使用不同的先进特征提取算法的平均识别率在98%以上。与此同时,如何找到一种强有效的方法来对虹膜区域进行准确而高效的分割成为了一个瓶颈。传统的分割方法需要大量的阈值和边缘检测,或需要在很大的参数空间表决,这些方法不仅难以操作而且耗时严重。文中提出了一种强有力的基于曲线拟合的虹膜区域分割方法,通过基于虹膜数据库THU-V1和CASIA-V1的测试证明:即使在严重的睫毛遮挡情况下,该方法也是非常有效和准确的。     

基于云理论的曲线拟合优化研究

为了提高曲线拟合的效率,提出了一种基于云理论的曲线拟合方法,并进行了优化研究,详细论述了实现的过程以及关键技术.通过实验表明,该方法取得了良好的实验效果,是实现曲线拟合的实用工具.     

Multigrid computation for curve fitting in the wavelet domain

A multi-layer multigrid algorithm for curve fitting in the wavelet domain is presented. This algorithm is achieved by applying a wavelet transform to each grid of the conventional multigrid structure. Using a wavelet transform, the convergent rate in each grid is improved and the total system can converge more quickly     

神经网络曲线拟合在温补晶振上的应用

石英晶振作为重要的频率源器件,其频率稳定度至关重要。但温度对石英晶振的影响很大。传统的微处理器温度补偿晶振中在拟合曲线时算法简单,导致软件引起的误差较大。利用了神经网络算法在曲线拟合上的应用,拟合出补偿电压与温度之间的函数关系,微处理器根据温度传感器采集的温度控制AD芯片产生补偿电压,从而使压控振荡电路输出稳定的频率的目的。实验结果表明:温度在-10⁸0℃时,频率稳定度达到±0.35 ppm,比未补偿时提高了近20倍,比其他曲线拟合方法得出的效果要好。     

基于正弦曲线拟合的快速限流预测算法

传统的单纯由硬件电路实现的限流器针对电流突然上升的情况不能及时做出反应,而基于嵌入式软件实现的限流器能根据采集的电流数据通过算法处理及时做出预测,使电流峰值还未出现就可以计算出其幅值并及时做出反应。本文介绍了一种基于微控制单元(MCU)实现的快速限流预测算法,该算法可以把采集到的受噪声等影响的电流数据拟合成接近理想的正弦曲线,预测求解出电流幅度,从而快速判断电流的峰值是否达到限流器的限流标准,当电路中电流突然超过30 mA或5倍以上时,在规定时间内实现脱扣。经过多次实验可以验证本算法能够准确预测出电流幅值是否达到脱扣条件。     

基于小波分析的分形参数估计新方法

该文研究目的是估计1/f类分形随机过程参数矢量 (, 2,2w)。作者基于小波分析,对1/f过程观测值的小波系数方差进行一系列代数运算,并给出详尽的证明过程,最终求取了噪声中分数布朗运动(fBm)参数矢量的估计量。实验结果表明,与传统的极大似然估计(ML)相比,算法简洁,效果良好,估计参数范围广泛,同时对噪声也不再局限于高斯分布。     

I/f噪声源及MOS器件中的1/f噪声

1／f噪声,由于其反映了器件的质量、可靠性等参数,其研究越来越为人们所重视。本文首先较为系统地介绍了1／f噪声源两种较为成熟的理论：载流子数涨落和迁移率涨落模型,最后将研究MOS晶体管中1／f噪声的现象。在n管中,较为成功地用△N模型;而在PMOS晶体管中,△μ模型可较为成功地解释其1／f噪声特性。     

1/f noise

1/f noise is a nonstationary random process suitable for modeling evolutionary or developmental systems. It combines the strong influence of past events on the future and, hence somewhat predictable behavior, with the influence of random events. Nonstationary autocorrelation functions for 1/f noise are developed to demonstrate that its present behavior is equally correlated with both the recent and distant past. The minimum amount of memory for a system that exhibits 1/f noise is shown to be one state variable per decade of frequency. The system condenses its past history into the present values of its state variables, one of which represents an average over the most recent 1 unit of time, one for the last 10 time units, 100 units, 1000, 10000, and so on. Each such state variable has an equal influence on present behavior.     

Image super-resolution by curve fitting in the threshold decomposition domain

A new curve-fitting scheme is proposed in this paper to produce super-resolution images from a single low-resolution source image. The most unique feature of this method is that the threshold decomposition is performed on the given source image to obtain multiple binary images so that the curve-fitting applied on each resulted binary image can be made very efficient and accurate, thus allowing us to focus on tiny objects and thin structures so as to achieve rather nice visual results even when a large up-scaling factor is used. Two novel techniques are further proposed to improve the visual quality: (1) a spreading technique (applied on some significant pixels detected in each threshold decomposed binary image) is used to remove ladder-like false edges that often appear visually in super-resolution images, and (2) an edge correction (guided by the edge information extracted from the original source image) is used to sharpen all inherent edges. Our results are compared with those achieved by using the state-of-arts techniques, showing the ability of our algorithm to achieve a better visual quality in smooth areas as well as for sharp edges and small objects.     

二次曲线拟合在煤灰分计算中的应用

介绍基于双能量γ射线透射法测量煤灰分原理的二次曲线拟合算法,解决传统同一矿源煤灰分测量直线拟合算法过程烦琐和有效测量范围小等问题,简要介绍最小二乘法的基本原理以及传统直线拟合算法的数学模型,并用MATLAB进行仿真对比,通过对结果进行误差分析,验证二次曲线拟合算法的可行性。