傅里叶变换与小波变换的统一数学模型

提出了建立信号变换统一数学模型的设想,阐述了这一设想的意义;提出了域参变量、域参函数等概念;探索并建立了傅里叶变换(短时傅里叶变换)与小波变换统一数学模型的普通形式和广义形式,绘出了统一数学模型的流程图,给出了统一数学模型的物理意义;给出了傅里叶变换、短时傅里叶变换与小波变换在统一数学模型中的各参量和参变函数的取值。     

用快速傅立叶变换进行再现平面四杆机构连杆曲线的综合

利用信号分析中的快速傅立叶变换（简称FFT）,把连杆机构中,连杆上的曲线用它所含的谐波分量来表示。这样就可以根据连杆曲线所含的谐波分量对连杆曲线进行识别和选取。根据这些谐波分量,我们还可以得到有关连杆曲线的速度和加速度信息。这对于连杆机构连杆曲线的分析与综合有比较重要的意义。把不同的连杆曲线所对应的结构尺寸及所含的谐波分量一起存到一个数据库中,于是就得到一个有关连杆曲线的数值图谱。以四杆机构为例,得到了含16728条曲线的图谱,利用该图谱进行连杆曲线的分析与综合,要比传统图谱方便且精确。     

DEVELOPMENT AND ANALYSIS OF TIME VARIANT DISCRETE FOURIER TRANSFORM ORDER TRACKING

Several of the common order tracking methods for solving noise and vibration problems of rotating machinery are reviewed. These methods include the fast Fourier transform (FFT) and resampling based order tracking algorithms. The time variant discrete Fourier transform (TVDFT) is developed as a new and alternative order tracking method. This method contains many advantages which the current order tracking methods do not possess. The TVDFT has the advantage of being very computationally efficient as well as the ability to minimise leakage errors. The basic TVDFT method may also be extended to a more complex method through the use of an orthogonality compensation matrix which can separate closely spaced orders as well as separate the contributions of crossing orders. The basic TVDFT is a combination of the FFT and the resampling based methods, a special case of the chirp-z transform. This method can be formulated in several different manners, one of which will give results matching the resampling based methods very closely. Both analytical and experimental data are used to establish the behavioural characteristics of this new method.     

基于快速傅里叶变换和共轭梯度法求解干接触问题

为求解粗糙表面弹性接触问题,将其转化为一个线性补余能问题,进而简化为一个二次函数的条件极值问题,利用共轭梯度法求解。算法实现了在共轭梯度方向上修正步长的优化,有效地提高了收敛效率。而占用大量计算时间的弹性变形求解采用快速傅里叶变换(Fast Fourier transform,FFT)技术,该算法有效地克服了传统傅里叶变换所引起的周期性误差。计算实例模拟了点接触单峰表面,正弦表面和真实粗糙表面的弹性接触以及有限长滚子线接触等接触问题。计算结果显示目前所用算法有效地缩短了干接触弹性接触问题的求解时间,对于不同的粗糙表面和接触类型都表现出一致的良好收敛性,同时计算精度对网格的依赖性很小,是工程中有效的分析设计工具。     

DISCRETE WAVELET TRANSFORM FOR DENOISING RAMAN SPECTRA OF HUMAN SKIN TISSUES USED IN A DISCRIMINANT DIAGNOSTIC ALGORITHM

In this work, we applied the discrete wavelet transform (DWT) method as a denoising tool for dispersive Raman spectra of skin samples, and we compared the results obtained with the low-order polynomial fitting in a discriminating model based on principal components analysis (PCA). We used a set of 50 Raman spectra of skin tissue fragments diagnosed as normal (N) (25 spectra) and basocellular cell carcinoma (BCC) (25 spectra). A denoising procedure using DWT and its inverse was employed, and the resulting spectra were compared to denoising using low-order polynomial fitting and adjacent averaging smoothing. The tissue spectral profile showed changes in the intensity of bands below 1400 cm^?1 for DWT compared to the denoising by polynomial and smoothing. By applying PCA and Mahalanobis distance in both groups processed, we verified that the filtering method does not alter significantly the discrimination of N and BCC tissues. However, the DWT denoising presented an interesting result, which showed the main components after decomposition of the Raman signal used in the reconstruction.     

DETECTION OF INCIPIENT LOCALIZED GEAR FAULTS IN GEARBOX BY COMPLEX CONTINUOUS WAVELET TRANSFORM

As far as the vibration signal processing is concemed, composition of vibration signal re-sulting from incipient localized faults in gearbox is too weak to be detected by traditional detectingtechnology available now.The method, which includes two steps: vibraton signal from gearbox is firstprocessed by synchronous average sampling technique and then it is analyzed by complex continuouswavelet transform to diagnose gear fault, is introduced. Two different kinds of faults in the gearbox, i.e.shaft eccentricity and initial crack in tooth fillet, are detected and distinguished from each other suc-cessfully.     

离散小波变换和互相关函数幅值向量在复合材料层合结构损伤检测中的应用

提出一种随机激励下的结构损伤检测方法。首先选取双正交小波函数对结构在随机激励下的时域响应进行一维离散小波变换(discrete wavelet transform,DWT),然后利用重构的包含最低频率信息的近似信号计算互相关函数幅值向量(cross correlation function amplitude vector,CorV)。利用结构损伤前后CorV差的二次差分作为损伤检测的指标。与直接利用振动响应原始信号计算CorV来检测损伤的方法相比,该方法能更准确地进行复合材料层合结构分层损伤定位。通过对带有不同位置分层损伤的复合材料层合板损伤检测的数值仿真,验证用文中方法检测复合材料层合结构分层损伤的有效性。     

用子波变换提取CO2焊焊穿信息特征的研究

介绍子波变换及离散二进子波变换,分析快速子波变换——Ｍａｌａｔ算法,并阐述了利用子波变换模极大值检测信号奇异性方法的原理,给出了应用该方法提取ＣＯ２气体保护薄壁（板）焊工件焊穿信息特征的成功应用实例,说明这种方法能够有效地应用于焊接过程质量监控的信号处理。     

DETERMINATION OF HYDROXYPYRENE TRISULFONATE BY TWO WAVELENGTH EXCITATION FLUORESCENCE USING A ONE MICROLITER CAPILLARY

Fluorescence is a type of electromagnetic spectroscopy that employs emission from a sample. It involves using a beam of light that excites the electrons in specific compounds and causes them to emit light of a lower energy. As proof of principle, a computer controlled experiment is described employing a single microliter capillary tube setup, using a two wavelength excitation of a single wavelength emission of hydroxypyrene trisulfonate. The same setup can be manipulated for the other pH-sensitive fluorescence ratiometric systems. In addition, this setup can be scaled up for high-throughput measurements.     

DETERMINATION OF TRACE ELEMENTS OF EMBOLI (CLOT) IN THE CARDIOVASCULAR SYSTEMS OF PATIENTS BY ENERGY DISPERSIVE X-RAY FLUORESCENCE ANALYSIS

ABSTRACT

An energy dispersive x-ray fluorescence analysis is applied for determining the spatial distribution of elemental concentrations of emboli in the vascular system. The fluorescent Kα x-rays of elements were detected so that the elemental concentration could be determined for these elements. For this measurement, Am-241 and Fe-55 radioisotopes were used for excitation of samples and a Si(Li) detector together with an ND66B multichannel analyzer was used for counting of Kα x-rays.     

DETERMINATION OF SELECTED METALS IN ALLIGATOR (Alligator mississippiensis) TISSUES BY INDUCTIVELY COUPLED PLASMA-OPTICAL EMISSION SPECTROMETRY

The results presented in this preliminary study show the concentrations of selected metals in the muscle and bone tissues from the tail of an alligator (Alligator mississippiensis) as determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). Cadmium and lead were not detected above the approximate detection limit of 0.5 µg/g for these two metals by ICP-OES, in either meat or bone tissues. Concentrations (µg/g) (mean ±standard deviation, range) for copper were 8.8 ± 3.8, 6.5–13.1 (meat), and 6.2 ± 3.5, 3.6–10.2 (bone); for iron were 41.9 ± 16.2, 28.8–59.9 (meat), and 26.4 ± 4.4, 21.3–29.0 (bone); and for zinc were 52.8 ± 7.4, 48.0–61.4 (meat), and 42.7 ± 9.0, 34.9–53.2 (bone). The results of copper, iron, and zinc levels were not considered to be potentially toxic to the alligator.     

DETERMINATION OF CADMIUM,CHROMIUM, LEAD,AND MERCURY IN POLYETHYLENE AND POLYPROPYLENE AFTER XYLENE TREATMENT BY ENERGY DISPERSIVE X-RAY FLUORESCENCE SPECTROMETRY

A convenient organic solvent treatment method was developed for the determination of Cd, Cr, Hg, and Pb in polyethylene and polypropylene matrices by energy dispersive X-ray fluorescence spectrometry. The solvent treatment method had many advantages for the fast, simple, and accurate multi-element analysis of these materials. Calibration curves were prepared using organometallic compounds in xylene in the concentration range of 1–80 mg kg^?1. The prepared samples had a homogeneous elemental distribution and good durability. The trueness for the quantification of mentioned elements were checked by using a polyethylene certified reference material. The apparent recoveries of the elements with certified values were in the range of 0.81 (Hg) to 1.14 (Pb). The precision was normally better than 8% RSD, with the exception of Hg (10%). The method detection limits were found to be 12, 24, 12, and 12 mg kg^?1 for Cd, Cr, Hg, and Pb, respectively. Polyethylene and polypropylene samples were analyzed by both the XRF method and the reference technique for comparative purposes. Application of analysis of variance (ANOVA) showed no differences between the mean results. The proposed method could be also applied to several different xylene soluble plastics.