Boxcar滤波器和极化Refined Lee滤波器对极化SAR分类精度影响的评估

本文阐述了Boxcar滤波器和极化Refined Lee滤波器的滤波原理,比较了两种滤波器的滤波效果。通过滤波后的极化图像分类精度的比较发现,滤波能显著提高监督分类的精度,滤波是提高分类精度必不可少的技术环节,Boxcar滤波在提高分类精度方面要优于Refined Lee滤波,此外滤波窗口的大小对分类精度也有重要的影响。     

基于奇异值的联邦滤波器信息分配新方法

针对有状态重置结构的联邦滤波器,在分析以往信息分配和重置方法的基础上,提出了一种基于估计协方差阵奇异值动态确定信息分配系数的算法.结合INS/GPS/DVS/APS组合导航系统的Monte-Carlo数字仿真结果表明:与以往算法和无重置联邦滤波比较,该算法在联邦滤波器的主滤波器信息融合周期长于局部滤波周期时,可有效提高系统状态估计误差精度.     

有源滤波器（APF）和高压直流输电

在构成高压直流输电系统一系列关键技术中,滤波装置占据十分重要的地位。本文主要介绍有源滤波器的构成,工作原理及分类;分别对HVDC系统中直流侧及交流侧的有源滤波器进行分析比较;在此基础上,对高压直流输电中的滤波装置做一定的展望。     

应用ICA滤波器技术提取图像纹理特征

针对纹理图像分类问题,本文提出了一种应用ICA滤波器技术提取图像纹理特征的方法.该方法首先从训练图像集中随机抽取图像块作为观测信号,应用ICA技术,提取滤波器组.然后根据训练样本图像对滤波器组的响应值来评估和选择滤波器组,达到降维的目的.最后利用滤波器组对测试图像进行滤波,得到该图像的滤波响应结果,从该响应结果中得到最大响应滤波器编号,提取其直方图作为图像的全局特征和局部特征.对Brodatz纹理图像集中108个纹理类别进行了分类实验,结果表明,与MPEG-7纹理描述子相比,该图像特征对纹理图像具有更好的分类效果.     

图像去椒盐噪声滤波器的研究

在图像平滑过程中,如何滤除噪声同时保护图像的细节是一个研究热点.本文提出并设计一种将十字窗和叉形窗有机结合的多窗口自适应中值滤波器(MWMF滤波器),可根据窗口内图像自身的形状,自适应地选择十字窗和叉形窗.在比较多窗口自适应中值滤波和形态滤波这两种滤波器的优缺点之后,还提出并设计了非线性组合滤波器.实验表明该滤波器滤除椒盐噪声的效果优于单独使用中值滤波或形态学滤噪,在椒盐噪声概率超过0.2时优势尤为明显.     

表面计量中高斯滤波器的一种高精度实现算法

为了能高精度地实现表面计量中的高斯滤波,基于中心极限定理,提出了一个高斯滤波器的二阶巴特沃思滤波器逼近数学模型．用双线性变换法设计了IIR型数字高斯逼近滤波器．逼近精度可以通过调节逼近滤波器的级联阶数实现．在八阶级联的条件下,高斯逼近滤波器与高斯滤波器的幅度传输特性偏差大约只有0．25％．高斯逼近滤波器采用迭代算法实现,算法简便,易于实现．迭代算法通过合理选择初始值,可以有效抑制边缘效应．实验结果表明,在普通的双核计算机上提取11200点数据的表面中线仅需约160ms,在高精度地实现高斯滤波特性的同时,还有效地抑制了边缘效应．     

自适应M滤波器及其噪声图象滤波

为了滤除多种噪声,保持图象边缘,本文在稳健统计理论基础上,提出一种新的稳健非线性滤波器——自适应M滤波器。重点研究M滤波器的滤波特性,边缘保持特性和滤波参数的自适应性。在一维和二维含有尖锐边缘的噪声信号滤波中,评价了自适应M滤波器的性能。理论分析和实验结果表明,自适应M滤波器在噪声滤波和边缘细节保持方面均优于中值滤波器、滑动均值滤波器和α-裁剪均值滤波器。还研究了最大/最小估计滤波器(M)、广义排序统计滤波器(L)和秩排序统计滤波器(R)三类著名非线性滤波器的内在关系,得到一些有意义的结果。     

IIR数字滤波器在定点DSP上的实现

介绍了IIR(InfiniteImpulseResponse)数字滤波器在Motorola56300系列的定点DSP(DigitalSignalProcessor)上的实现方法,给出了双二阶滤波器的单精度和双精度两种设计,并比较了它们的精度。同时还给出了源程序,对在Motorola的DSP上实现双二阶滤波器具有一定的参考价值。     

基于傅立叶变换的数字滤波器的设计

本设计介绍了一种不同于传统数字滤波器的新型数字滤波器,该滤波器是以离散傅立叶变换和反变换为基础设计的.通过对信号的离散傅立叶变换,得到一组幅度和频率对应的变换值,根据滤波器要求,使不满足要求的频率点对应的幅度值为零,得一组新数据,对这组新数据进行离散傅立叶逆变换,结果即为滤波后的信号.其幅频特性近乎理想特性.     

用于减小随机误差的中值—模糊滤波器

本文详细地论述了中值－模糊滤波器的基本原理和隶属函数的建立方法，这种滤波器能同时抑制信号中的高斯白噪声和脉冲型噪声，有效地减小随机误差，提高测量精度。     

Comparative evaluation of despeckle filtering in ultrasound imaging of the carotid artery

It is well-known that speckle is a multiplicative noise that degrades the visual evaluation in ultrasound imaging. The recent advancements in ultrasound instrumentation and portable ultrasound devices necessitate the need of more robust despeckling techniques for enhanced ultrasound medical imaging for both routine clinical practice and teleconsultation. The objective of this work was to carry out a comparative evaluation of despeckle filtering based on texture analysis, image quality evaluation metrics, and visual evaluation by medical experts in the assessment of 440 (220 asymptomatic and 220 symptomatic) ultrasound images of the carotid artery bifurcation. In this paper a total of 10 despeckle filters were evaluated based on local statistics, median filtering, pixel homogeneity, geometric filtering, homomorphic filtering, anisotropic diffusion, nonlinear coherence diffusion, and wavelet filtering. The results of this study suggest that the first order statistics filter lsmv, gave the best performance, followed by the geometric filter gf4d, and the homogeneous mask area filter lsminsc. These filters improved the class separation between the asymptomatic and the symptomatic classes based on the statistics of the extracted texture features, gave only a marginal improvement in the classification success rate, and improved the visual assessment carried out by the two experts. More specifically, filters lsmv or gf4d can be used for despeckling asymptomatic images in which the expert is interested mainly in the plaque composition and texture analysis; and filters lsmv, gf4d, or lsminsc can be used for the despeckling of symptomatic images in which the expert is interested in identifying the degree of stenosis and the plaque borders. The proper selection of a despeckle filter is very important in the enhancement of ultrasonic imaging of the carotid artery. Further work is needed to evaluate at a larger scale and in clinical practice the performance of the proposed despeckle filters in the automated segmentation, texture analysis, and classification of carotid ultrasound imaging.     

噪声概率快速估计的自适应椒盐噪声消除算法

提出一种可识别噪声概率自动调节滤波窗口的自适应椒盐噪声消除算法。对非理想椒盐噪声污染图像随机区域进行变窗口中值滤波,将结果与滤波前比对获得噪声点数,滤波区域即按此点数排序。然后取每种滤波窗口下的中间三组数据,该数据平均加权获取图像噪声概率初估计,对初估计平均加权即得图像噪声概率。滤波前首先采用阈值法排除明显噪声点,剩余像素中再以离窗口中心像素距离平方的倒数为权值估计中心像素。最后由噪声概率按照T-S模糊规则对不同模型的输出估计值进行融合。实验证明,与传统中值滤波等算法相比,该算法具有噪声自动估计和自适应窗口调节能力,滤波后标准均方差可减少20%以上,速度可提高一倍多。     

Validation of the multiaxial racetrack amplitude filter

Amplitude filters are a most important tool in practical fatigue analyses to manage their computational cost when, as usual, the measured load history is noisy, oversampled, too long, and/or contains too many non-damaging low-amplitude cycles or events. To reduce the calculation burden, such filters should not only eliminate noise and remove redundant oversampled data from the measured signal, but also neglect small amplitudes that do not cause fatigue damage. The veteran racetrack filter can perform all such tasks efficiently, however it is limited to uniaxial load histories. Multiaxial filtering techniques have been proposed in the past, however they fail to identify the most damaging events in several non-proportional histories, in addition to losing information on the load path shape. In this work, a new, fast, and efficient multiaxial version of the traditional racetrack filter is proposed to solve these issues, synchronously filtering complex loading histories while preserving all their significant reversals and equivalent ranges, and their load path shape as well, a most important feature for multiaxial fatigue analyses. Six and three-dimensional versions of the filter are proposed, respectively for invariant-based and critical-plane damage calculation approaches. The method allows not only the proper filtering of stress/strain histories at a given material point, but also of any history of multi-dimensional quantities such as forces, moments, and/or displacements acting at different points of a structure. The filter efficiency is evaluated from tension–torsion experiments in 316L stainless steel tubular specimens with challenging non-proportional path shapes.     

自洁式过滤器与板式高效过滤器比较

介绍C55M×3型和C95055M×3型离心空压机入口分别采用板式高效过滤器和自洁式过滤器的使用情况,从过滤效果、空压机运行状况以及经济性3方面对两种过滤器进行了分析比较,阐述改善自洁式过滤器过滤效果的措施以及自洁式过滤器和板式高效过滤器较经济的使用场合。     

表面粗糙度测量中的高斯滤波快速算法

应用高斯函数的逼近法和冲激响应不变法,设计出用于表面粗糙度测量的高斯数字滤波器,并给出了其零相移的递归滤波算法,算法简洁,易于实现。递归计算方法的计算量小,计算效率高。适当增加滤波器节数,在不增加很多计算量的情况下,可以达到很高的精度。文中给出的滤波器例子,传输偏差大约为2％和1％,处理一次表面测量轮廓数据,在当今最普通的计算机上,滤波时间小于1s。     

Application of the Taguchi approach of the design of experiments for determination constructional and working parameters of the linear Venetian blind microdroplet filter

The aim of the investigations presented in the paper was to study the influence of constructional and working parameters of the linear Venetian blind electrostatic filter on its filtering efficiency and to determine optimal conditions for the filter exploitation. The flow of titanium vacuum-arc plasma, produced in DC discharge with superimposed high-current arc pulses, through the linear Venetian blind filters of different construction was investigated. The dependences of the filtering efficiency and the ion current intensity on the gas pressure, arc pulses frequency, distance and tilt angle of the filter blinds were determined. The plan of the experiment was developed using Taguchi method and the conditions, which guarantee maximal cleaning efficiency at maximal plasma transmission through the filter were determined for Ti. Based on the obtained results the initial construction of the filter was modified. The angular distribution of microdroplets generated from titanium cathode and reaching the substrate was investigated in two configurations - without and with the electrostatic filter.     

Adaptive-neighborhood filtering of images corrupted by signal-dependent noise

In many image-processing applications the noise that corrupts the images is signal dependent, the most widely encountered types being multiplicative, Poisson, film-grain, and speckle noise. Their common feature is that the power of the noise is related to the brightness of the corrupted pixel. This results in brighter areas appearing to be noisier than darker areas. We propose a new adaptive-neighborhood approach to filtering images corrupted by signal-dependent noise. Instead of using fixed-size, fixed-shape neighborhoods, statistics of the noise and the signal are computed within variable-size, variable-shape neighborhoods that are grown for every pixel to contain only pixels that belong to the same object. Results of adaptive-neighborhood filtering are compared with those given by two local-statistics-based filters (the refined Lee filter and the noise-updating repeated Wiener filter), both in terms of subjective and objective measures. The adaptive-neighborhood approach provides better noise suppression as indicated by lower mean-squared errors as well as better retention of edge sharpness than the other approaches considered.     

锥形粉末冶金过滤器的研制

较详细地论述了不锈钢粉末冶金过滤器的制造工艺及原始粉末形状、粒度、压制压力和烧结温度对过滤性能的影响。采用合理的工艺参数研制出性能达到国际水平的不锈钢粉末冶金过滤器并已用于生产。     

基于谱直方图表示和支持向量机的纹理分类

在纹理分类中采用谱直方图表示(SHR),每个图像窗表示一个包含滤波后图像直方图的特征向量,而直方图是图像谱表示的连接桥梁.在滤波器选择算法之前,结合每个图像分块和滤波器的独立谱表示和直方图,可以获得更加低层的局部特征.最后,时所有独立滤波器采用滤波器选择算法来得到所需的少量滤波器.为了保证分类的可靠性,选择高斯径向基函数(RBF)进行谱直方图表示,采用支持向量机(SVMs)作为分类函数.对本文方法和其它两种方法:Gabor滤波和独立成分分析(ICA)进行了纹理分类和脸部识别的比较实验.实验结果表明,本文方法具有更高的分类准确性,也证明了SVMs优秀的泛化能力.