基于小波变换的零件图像融合与边缘检测

提出基于小波变换的零件图像数据融合和边缘检测的方法,对图像进行分解,将高频区域中的绝对值较大的系数作为重要小波系数;在低频区域,对逼近系数进行加权平均得到新的逼近系数,然后进行小波重构实现图像数据融合。应用小波变换对融合图像进行多尺度边缘检测,获取图像边缘,或对图像进行小波多尺度边缘检测,然后融合边缘。     

小波变换在螺纹边缘检测中的应用

螺纹牙型图像的边缘是检测螺纹的主要特征，边缘提取的质量将直接影响检测精度。根据螺纹图像边缘的特点，利用小波变换对目标图像进行降噪和边缘特征处理。其效果明显好于用经典的边缘检测算子，实验说明，小波变换对于提高螺纹的检测精度有重要价值。     

一种基于小波变换的照明无关边缘检测和模糊增强方法

提出了一种基于小波变换的照明无关边缘检测和模糊增强算法,用于从不均匀的弱照明图像中提取目标边缘。依据照明反射图像形成模板和CCD相机成像公式,推导出图像的小波变换公式。对图像局部区域中边缘与背景像素的小波系数进行比较分析,设计了一种照明无关的小波边缘检测公式。给出一种同时考虑小波模值大小和梯度方向的模糊算子来增强边缘并抑制噪声。最后,采用仿真和真实的图像对该算法进行验证,利用此算法检测阶梯边缘,得到该算法的边缘检测评价标准F系数值为0.984 3,边缘定位精度评价系数E_d值为0.126 5,通过被检测的特征球边缘计算得到的交比值误差为3.72×10^-3。实验结果证实,该边缘检测方法能够很好地工作于非均匀的弱照明图像。     

A high-pressure cell for kinetic studies on gas hydrates by powder x-ray diffraction

A new high-pressure-low-temperature cell was developed for in situ observations of gas hydrates by powder x-ray diffraction. The experimental setup allows investigating hydrate formation and dissociation as well as transformation processes between different hydrate crystal structures as a function of pressure, temperature, and feed gas composition. Due to a continuous gas flow, the composition of the gas phase is kept constant during the whole experiment. This is crucial for the formation of mixed hydrates formed from feed gas mixtures that contain one or more components in low concentrations. The pressure cell can be used in a pressure range between 0.1 and 4.0 MPa and a temperature range between 248 and 298 K. First results of time-resolved measurements of a mixed structure II CH(4) + iso-C(4)H(10) hydrate and a structure I CO(2) hydrate are presented.     

An algorithm for the continuous Morlet wavelet transform

This article consists of a brief discussion of the energy density over time or frequency that is obtained with the wavelet transform. Also an efficient algorithm is suggested to calculate the continuous transform with the Morlet wavelet.The energy values of the wavelet transform are compared with the power spectrum of the Fourier transform. Useful definitions for power spectra are given.The focus of the work is on simple measures to evaluate the transform with the Morlet wavelet in an efficient way. The use of the transform and the defined values is shown in some examples.     

小波变换在早期损伤识别中的应用

提出了小波变换用于早期损伤的识别的方法.对小波理论做了简介,并通过仿真实验验证小波变换对损伤识别的能力.通过观察连续小波变换(CWT)的小波系数的模极大值或者离散小波变换(DWT)中的细节信号,识别动(静)态信号中的奇异值,从而判别出损伤的位置.此方法仅需要有损伤的结构的响应信号,不需要未损伤结构的响应信号及其结构信息,所需的信号可以是静态的,也可以是动态的.将该方法应用到带裂纹的悬臂梁有限元模型,通过瞬态、静力分析采集信号,精确定位裂纹的位置和数量.与传统方法相比,该方法不仅可行性强,经济方便,而且检测结果更为精确可靠.仿真实验表明,小波变换的方法是有力可靠的结构早期损伤识别方法.     

Periodic trend detection from CMM data based on the continuous wavelet transform

The main goal of this paper is to describe a method based on the continuous wavelet transform (CWT). The Shannon entropy of CWT coefficients in each scale is calculated in order to detect the characteristic trends of the CMM measurement data efficiently. This method is successfully implemented in a body-in-white (BIW) assembly for the detection of periodic trends in coordinate measure machine (CMM) data. It would contribute to main cause location in BIW quality control. The principle of the CWT and the property of the periodic trend after the CWT are explained from a mathematical viewpoint. An actual quality-control case is analyzed using the CWT method. Consistency between the results and the actual situation proves the effectiveness of this CWT method.     

一种改进的小波域去噪算法

在Donoho D L和Johnston IM提出的多分辨分析小波阈值去噪方法的基础上,提出了一种新的双变量阈值函数。采用新的阈值函数的去噪效果无论在视觉效果,还是在信噪比增益和最小均方意义上均优于传统的硬阈值和软阈值,克服了采用硬阈值法去噪效果不佳和软阈值法过度光滑使信号失真的缺点。通过仿真实验结果,表明该方法的有效性和优越性。     

Higher-density dyadic wavelet transform and its application

This paper proposes a higher-density dyadic wavelet transform with two generators, whose corresponding wavelet filters are band-pass and high-pass. The wavelet coefficients at each scale in this case have the same length as the signal. This leads to a new redundant dyadic wavelet transform, which is strictly shift invariant and further increases the sampling in the time dimension. We describe the definition of higher-density dyadic wavelet transform, and discuss the condition of perfect reconstruction of the signal from its wavelet coefficients. The fast implementation algorithm for the proposed transform is given as well. Compared with the higher-density discrete wavelet transform, the proposed transform is shift invariant. Applications into signal denoising indicate that the proposed wavelet transform has better denoising performance than other commonly used wavelet transforms. In the end, various typical wavelet transforms are applied to analyze the vibration signals of two faulty roller bearings, the results show that the proposed wavelet transform can more effectively extract the fault characteristics of the roller bearings than the other wavelet transforms.     

Comparison between beryllium and diamond-backing plates in diamond-anvil cells: application to single-crystal x-ray diffraction high-pressure data

A direct comparison between two complete intensity datasets, collected on the same sample loaded in two identical diamond-anvil pressure cells equipped, respectively, with beryllium and diamond-backing plates was performed. The results clearly demonstrate that the use of diamond-backing plates significantly improves the quality of crystal structure data. There is a decrease in the internal R factor for averaging, structure refinement agreement factors, and in the errors and uncertainties of the atomic coordinates, atomic displacement parameters, and individual bond lengths.     

基于小波变换的正则化盲图像复原算法

提出了一种将小波变换和自适应正则化方法相结合的盲图像复原算法。该算法先对退化后的图像进行小波分解,得到图像在不同子频段的信息;然后针对各个子频段内图像的频率和方向特性,使用不同的自适应正则化复原方法,在图像的低频子频段进行去模糊;高频子频段则进行抑制噪声和保边缘特征;最后通过小波逆变换得到复原后的图像。实验结果表明, MSE减少了1.60,信噪比增量为1.76,算法性能和复原效果相对空间自适应正则化方法,都有一定的提高。     

一种小波变换与矢量量化结合的图象压缩编码算法

本文提出了一种新的小波变换与矢量量化相结合的图象压缩编码算法.首先根据小波图象中各子带系数的带间相关性对其进行四叉树分类,然后利用同一子带内高频系数的兄弟相关性采用变换的方法进行系数重排,以产生新的树结构.最后,根据系数的重要性,利用剪枝算法从每棵树中提取一个矢量,进行矢量量化编码.试验证明,在较高压缩比的情况下,使用此方法得到的重构图象质量（视觉效果和峰值信噪比）比通常的小波压缩算法有了较大的提高.     

一种基于小波变换的煤矸石图像边缘检测方法

针对煤矸石在线识别与自动分选系统中的图像处理问题,采用小波变换的多尺度方法,研究了煤矸石图像的轮廓提取与边缘检测,通过图像消噪和边缘加强,对煤矸石图像进行了处理.研究结果显示,采用小波变换的边缘检测方法,可以有效地抑制噪声,准确提取煤矸石图像的边缘特征,有助于提高煤矸石的识别率.     

A data mining approach for fault diagnosis: An application of anomaly detection algorithm

Rolling-element bearing failures are the most frequent problems in rotating machinery, which can be catastrophic and cause major downtime. Hence, providing advance failure warning and precise fault detection in such components are pivotal and cost-effective. The vast majority of past research has focused on signal processing and spectral analysis for fault diagnostics in rotating components. In this study, a data mining approach using a machine learning technique called anomaly detection (AD) is presented. This method employs classification techniques to discriminate between defect examples. Two features, kurtosis and Non-Gaussianity Score (NGS), are extracted to develop anomaly detection algorithms. The performance of the developed algorithms was examined through real data from a test to failure bearing. Finally, the application of anomaly detection is compared with one of the popular methods called Support Vector Machine (SVM) to investigate the sensitivity and accuracy of this approach and its ability to detect the anomalies in early stages.     

Gearbox fault detection using Hilbert and wavelet packet transform

Demodulation is an important issue in gearbox fault detection. Non-stationary modulating signals increase difficulties of demodulation. Though wavelet packet transform has better time–frequency localisation, because of the existence of meshing frequencies, their harmonics, and coupling frequencies generated by modulation, fault detection results using wavelet packet transform alone are usually unsatisfactory, especially for a multi-stage gearbox which contains close or identical frequency components. This paper proposes a new fault detection method that combines Hilbert transform and wavelet packet transform. Both simulated signals and real vibration signals collected from a gearbox dynamics simulator are used to verify the proposed method. Analysed results show that the proposed method is effective to extract modulating signal and help to detect the early gear fault.     

A system of detection and data acquisition for time-of-flight neutron diffraction setups

A simple system of neutron detection and data acquisition is considered. It is composed of sector sets of ³He counters, timing amplifiers-discriminators, 8-stop time-to-digital converters (TDCs), and a gate duration generator, as well as branch and crate controllers coupled to a computer. The system is used in neutron diffraction setups on the neutron spallation source at the Institute for Nuclear Research. The output pulse from the timing amplifier-discriminator is timed with the fast electron component of an avalanche in the detector. Neutron time-of-flight spectra are formed by a TDC in its embedded memory over the recording enable time ranging from 1 to 63 ms. The TDC time range has 4096 gradations with time step of 0.125–128 μs. Fast data acquisition is ensured by the Linux kernel driver. The data acquisition software based on the Qt4 library recognizes modules in the CAMAC crate and displays spectra with their preliminary processing.     

A new large radius imaging plate camera for high-resolution and high-throughput synchrotron x-ray powder diffraction by multiexposure method

A new large radius imaging plate diffraction camera for high-resolution and high-throughput synchrotron x-ray powder diffraction by means of multiple exposures has been developed for an insertion device beamline of SPring-8, Japan. The new imaging plate camera consists of a large radius cylindrical shape imaging plate cassette that is 400 mm in length and 954.9 mm in cylinder radius. The cassette is designed to be mounted on the 2 theta arm of the diffractometer of BL15XU in SPring-8. One imaging plate covers 24 degrees and several times of exposure changing the 2 theta-setting angle is necessary to obtain whole powder diffraction data up to a high angle region. One pixel of the imaging plate corresponds to 0.003 degrees in 2 theta when the readout pixel size is 50 microm squares. Separately collected data are translated to 2 theta-intensity format and are connected by comparing the peak and background intensity included in the overlapped area. The exposure time is less than 120 s for most samples and the readout time is about 3 min; thus, the total measurement time for one powder diffraction pattern is less than 20 min. The measurement time is the same order as the continuous 2 theta-scanning method of the third generation synchrotron powder diffractometer. The angular resolution of the new imaging plate camera was evaluated by comparing the full width at half maximum of the 111 reflection of NBS-Si. The observed angular resolution is not so high as a powder diffractometer with a Si or a Ge analyzer monochromator in the third generation synchrotron facility but higher than a powder diffractometer with a Ge analyzer monochromator at a bending magnet beamline of the second generation synchrotron. The Rietveld analysis of NBS-CeO2 was successfully carried out with the data taken by the new imaging plate camera.     

结点阈值小波包变换语音增强新算法

人耳频率分辨率是非线性的,而小波包算法有灵活的时频分析能力,可较好的模拟人耳基底膜的频率分析特性。本文提出了一种新的基于结点阈值的小波包变换语音增强算法。采用Bark尺度小波包对含噪语音进行分解,在语音信号的子带层次上进行阈值操作,并采用软阈值方法进行阈值处理。采用谱熵法估计结点噪声。实验表明,该算法在多种噪声,尤其是有色噪声和非平稳噪声条件下均有较好的语音增强效果。     

基于小波和混沌映射的函数水印算法

数字水印是保护数字产品的知识产权有效手段之一,用户通过在产品中嵌入秘密信息来达到保护的目的。提出了基于小波和混沌映射的函数水印算法,该算法利用用户定义的函数作为水印,通过小波变换嵌入到小波的高频区域,嵌入位置可由用户给定,位置信息由Logistic混沌算法加密后发给使用方,使用方在得到密钥和加密的位置序列后方可提取水印,通过对水印的相似度分析确定水印的正确性。实验表明,算法对用户使用方便、快捷,嵌入的水印透明度好,对于常见的攻击如压缩、加噪和剪裁等提取水印的相似度大于95%,具有良好的抗攻击性。     

提升小波变换在图像压缩中的应用

利用第二代小波变换--提升小波变换,为第一代小波变换提供了一种新的更快速的实现方法,使得其构造不再依赖于Fourier 变换构造,可以实现所有的第一代小波变换,提升方案把此变换过程分为分裂、预测和更新3个阶段.基于提升算法的小波变换是新一代静止图像压缩标准--JPEG 2000的核心算法之一.在研究小波提升方案的基础上,分析了它在JPEG 2000应用,最后将小波提升和Mallat算法进行分析比较,试验证明提升方案的小波变换算法计算时间比Mallat 算法减半.