一种新的小波滤波方法在化学谱图信号滤噪中的应用

仪器分析测定中，噪声的存在往往影响分析的准确度和仪器的检出限。小波变换多分辨分析的特性使得它成为一种很好的滤噪方法。基于小波分解后信号与噪声的小波系数随尺度变化规律不同的特性，提出了一种新的滤波滤方法-空域相关法，即通过不同尺度上相关系数模值与小波系数模模值的比较，达到滤波滤的目的。本文提出的方法具有无需人为选定无需人为选定滤噪阈值和小波函数、方法简单、失真度小等优点，可以大在提高信号的信噪比。模拟数据和ICP-AES实验数据证明了该方法的有效性。     

小波滤噪用于示波计时电位信号处理的研究

根据信号（Ｓ）和噪声（Ｎ）在小波变换下表现出的截然不同的性质,提出了一种新的滤噪方法,研究了噪音在不同细节的性质、滤噪阈值的确定及平滑与滤噪的特点。对不同Ｓ／Ｎ的示波计时电位信号进行了实验结果表明;小波滤噪在大大提高Ｓ／Ｎ的同时,信号强度基本不损失,优于传统的滤噪方法。     

毛细管电泳激光诱导荧光检测信号的小波滤噪

采用小波滤噪方法对毛细管电泳激光诱导荧光检测信号进行了处理，研究了小波变换中小波基的选择及噪声阈值的选择对滤噪的影响。结果表明，采用DB4小波基能有效消除毛细管电泳激光诱导荧光检测信号中存在的噪声，使信噪比得到较大改善。     

二进小波变换极大模法用于分析化学信号的滤噪

实验数据的滤噪在分析化学领域中具有重要的意义。小波变换技术具有很强的信号分离能力，容易把随机噪声从信号中分离出来，从而提高信号的信噪比。本文使用滤噪方法不同于传统离散小波变换方法，而是通过引入二进小波变换和李氏指数的概念，根据噪声与有用信号的极大模截然不同的特征，实现信号滤噪。实验数据的仿真结果研究也证明该方法的可行性。     

毛细管电脉在柱安培检测信号的小波滤噪研究

采用一种新的小波滤噪方法对毛细管电泳在柱安培检测信号进行了处理,研究了小波基的选择、噪音在不同细节中的特征以及噪音阈值的确定等,用此方法对酚类定量分析,结果信噪比、检测限和线性范围均有较大改善。     

利用二进样条小波模极大方法消除毛细管电泳信号噪声的研究

根据毛细管电泳信号中噪声与真实信号的模极大值特性之间存在较大差异的特点，提出了一种利用二进样条小波模极大值法去噪的方法研究了信号的半峰宽、不同信噪比以及阈值的选取对去噪结果的影响，并对模拟含噪信号和含噪毛经电泳信号去噪前后的结果进行了比较，实验结果表明，该法能效地消除谱带较宽的毛细管电泳等信号中存在的噪声。     

小波神经网络用于色谱数据的滤噪与压缩

介绍了小波神经网络（Ｗａｖｅｌｅｔ Ｎｅｕｒａｌ Ｎｅｔｗｏｒｋ）的结构和算法，并将其应用于色谱数据的滤噪与压缩。在小波神经网络中，采用了Ｂｕｂｂｌｅ母小波和一维搜索变步长共轭梯度优化方法。结果表明，小波神经网络将原始数据压缩至１：２０时，仍能得到很好的重建谱图。重建的色谱图不仅能保留原始的谱图特征而且有光滑滤噪的效果。对于色谱数据的存储与平衡滤噪具有重要意义。     

基于小波变换的航空润滑油酸值红外光谱分析

为利用红外光谱分析技术快速、准确测定在用航空润滑油酸值,将小波变换用于润滑油红外光谱预处理中,结合均值中心化法,提取光谱有效信息建模。光谱的小波变换选择符合光谱特征的db4小波为基函数,在分解尺度9下进行光谱分解,利用软阈值法滤除各层干扰噪声,重构消噪信号。该光谱预处理法与传统的Savitzky-Golay平滑导数结合均值中心化法相比,滤噪效果好,有效压缩了建模数据量。采用偏最小二乘法,选择最佳主因子数5,建立酸值模型,并对10个在用航空润滑油油样进行了分析。     

小波Fourier自去卷积法

使用小波函数作为Fourier自去卷积的截止函数，提出了小波Fourier自去卷积法.通过研究不同小波去卷积函数的性质，建立了消除伪峰的阈值法以及正负极值比的小波负峰扣除法，从而使经典Fourier自去卷积技术中存在的滤噪效果差、过程复杂、易出现伪峰及负峰等缺陷得以较好地解决.　将其用于示波计时电位法中多组分测定的结果表明该方法具有处理效果好、过程简单等优点.     

小波变换与分析化学信号处理

介绍了小波变换的基本理论并对小波变换的常用算法和应用进行了评述。由于小波变换的时2频局部化性质, 使其成为信号处理的强有力工具。在分析化学领域中, 小波变换在流动注射分析、伏安分析、高效液相色谱、红外光谱、质谱、核磁共振谱、可见-紫外光谱、光声光谱、扩展X-射线吸收精细结构(EXAFS) 谱等分析化学信号的平滑滤噪、数据压缩、重叠信号解析等方面都有成功的应用。     

小波降噪技术在差分吸收光谱浓度检测中的应用

为了实现对工业气体SO₂的浓度进行监控,基于紫外差分吸收光谱法开发了SO₂在线检测系统。针对系统噪声和Mie散射使吸收光谱叠加带来的误差,本文提出采用小波变换降噪技术代替传统光谱处理方法中的多项式平滑滤波技术来提高检测精度。通过对应用了Symlets、Daubechies、Coiflet和Biorthogonal这4种不同小波函数的实验数据分析和对传统小波阈值选取方式的改进,最终确定了基于rigisure阈值的小波阈值去噪的信号处理方法,并提出一种新的信噪比量来衡量信号处理的效果。这种方法可以快速可靠地处理光谱信号,处理后所得的监测浓度准确度基本控制在1.5%以内。在实验室环境下和工业现场环境下的大量实验结果表明本方法能有效的减小噪声对SO₂浓度监测带来的影响。     

分析化学信号在多尺度空间的滤噪

从多分辨率分析出发，结合离散正交小波变换(DWT)的理论，通过对各尺度下未抽取前的小波系数进行非线性滤波处理，达到在保护信号边缘的同时，有效实现白噪声及脉冲噪声的滤除。实验数据仿真结果研究也证明了该方法的可行性。     

Wavelet transform as a new approach to the enhancement of signal-to-noise ratio in anodic stripping voltammetry

De-noising signals is a frequent aim achieved by signal processing in analytical chemistry. The purpose is to enable the detection of trace concentrations of analytes. The limit of detection is defined as the lowest amount of analyte that still causes signals greater than the background noise. Appropriate de-noising decreases only the noise and maintains the measurement signal, so that signal-to-noise ratios are enhanced. One adequate mean of signal processing for this purpose is wavelet transform, which still is not a common tool in analytical chemistry. In this paper, the ability of de-noising by wavelet transform is shown for measurements in anodic stripping voltammetry using a hanging mercury drop electrode. The calculation of limits of detection and signal-to-noise ratios on the basis of peak-to-peak noise is exercised to quantify the performance of de-noising. Furthermore, signal shape with regard of easing the application of base lines is discussed. Different wavelet functions are used, and the results are compared also to Fourier transform. Coiflet2 was found out to reduce noise by the factor of 330 and is proposed as the adequate wavelet function for voltammetric and similar signals.     

基于小波的恒电量瞬态响应信号的滤波处理

利用小波变换的阈值法对恒电量响应信号进行滤波处理, 同时与传统的时域和频域的滤波方法进行分析比较, 并且讨论了小波变换的分解层数对恒电量响应信号滤波效果的影响. 结果表明, 利用小波变换可以在时域和频域同时对恒电量响应信号取得良好的去噪效果. 这不仅能提高时域曲线拟合的精度, 还大大地提高了恒电量频谱解析的可靠性. 在实际应用中, 小波变换的分解层数取5～7层可以收到满意的效果.     

Spatially adaptive stationary wavelet thresholding for the denoising of DNA capillary electrophoresis signal

The spatially adaptive thresholding based on the stationary wavelet transform was applied to the noise removal in the signal of DNA separated and determined by capillary electrophoresis. The threshold is derived in a Bayesian framework, and previously used on the wavelet coefficients is the generalized Gaussian distribution. The threshold is simple and closed form, which is adaptive to each subband because it depends on data-driven estimates of the parameters. Using this strategy, the noise in the signal of the DNA-separated analysis by capillary electrophoresis could be removed adequately. Experimental results show that the proposed denoising method is effective, and the spatially adaptive thresholding yields a lower root-mean-square error than the universal thresholding. The text was submitted by the authors in English.     

Selective removal of interference signals for near-infrared spectra of biomedical samples by using region orthogonal signal correction

New approach for chemometrics algorithm named region orthogonal signal correction (ROSC) has been introduced to improve the predictive ability of PLS models for biomedical components in blood serum developed from their NIR spectra in the 1280-1849 nm region. Firstly, a moving window partial least squares regression (MWPLSR) method was employed to locate the region due to water as a region of interference signals and to find the informative regions of glucose, albumin, cholesterol and triglyceride from NIR spectra of bovine serum samples. Next, a novel chemometrics method named searching combination moving window partial least squares (SCMWPLS) was used to optimize those informative regions. Then, the specific regions that contained the information of water, glucose, albumin, cholesterol and triglyceride were obtained. When an interested component in the bovine serum solution, such as glucose, albumin, cholesterol or triglyceride is being an analyte, the other three interests and water are considered as the interference factors. Thus, new approach for ROSC has employed for each specific region of interference signal to calculate the orthogonal components to the concentrations of analyte that were removed specifically from the NIR spectra of bovine serum in the region of 1280-1849 nm and the highest interference signal for model of analyte will be revealed. The comparison of PLS results for glucose, albumin, cholesterol and triglyceride built by using the whole region of original spectra and those developed by using the optimized regions suggested by SCMWPLS of original spectra, spectra treated OSC for orthogonal components of 1-3 and spectra treated ROSC using selected removing the highest interference signals from the spectra for orthogonal components of 1-3 are reported. It has been found that new approach of ROSC to remove the highest interference signal located by SCMWPLS improves of the performance of PLS modeling, yielding the lower RMSECV and smaller number of PLS factors.     

经验模态分解对瞬态电化学响应的滤波处理

用经验模态分解(EMD)对恒电量瞬态响应信号进行滤波处理. 通过计算机仿真实验评估EMD的滤波效果. 为了提高EMD滤波的实用性和减少滤波过程的主观性, 仿真实验主要针对混迭了白噪声、高频噪声和市电干扰以及上述混合噪声的恒电量瞬态响应. 在此基础上, 阐述了EMD滤波对多个时间常数恒电量瞬态响应的重要性, 并利用电化学阻抗谱结果验证了EMD滤波后的恒电量频谱. 结果表明, 经过EMD滤波的恒电量频谱和EIS有很好的相关性. 恒电量瞬态响应的EMD滤波, 采用前两项内在模函数(IMF)和IMF4的50 Hz成分置零的固定模式, 可以获得满意的滤波结果.     

纳米结构TiO2/聚3-甲基噻吩多孔膜电极光电化学研究

用光电流作用谱、光电流-电势图、紫外-可见吸收光谱等光电化学方法研究了导电玻璃(ITO)/TiO₂/聚3-甲基噻吩(PMT)电极的光电转换性质. 结果表明, PMT膜为p型半导体, 其禁带宽度为1.93 eV. 并通过循环伏安和光电化学方法确定了其导带位置为－3.44 eV, 价带为－5.37 eV, 在纳米TiO₂与PMT之间存在p-n异质结, ITO/TiO₂/PMT电极不仅提高了光电流, 而且使产生光电流的起始波长红移至＞600 nm, 从而提高了宽禁带半导体的光电转换效率.     

Applying a dynamic method to the measurement of ion mobility

A dynamic method is applied to measure the mobility of gas-phase ions in the dual ion funnel interface of the electrospray source of a quadrupole orthogonal time-of-flight mass spectrometer. In a new operational mode, a potential barrier was formed in the second ion funnel of the mass spectrometer and then progressively increased. In this region, a flow of gas drags the ions into the mass spectrometer while the electric force applied by the potential barrier decelerates them. Ions with lower mobility can be carried by the gas flow more easily than those with high mobility. Thus, electrical forces can block the more mobile ions more easily. Hence, the electric barrier formed in the ion funnel permits only ions below a certain mobility threshold to enter the mass spectrometer. When the barrier voltage is increased, this threshold moves from high to low mobilities. Ions with mobilities above the threshold cannot enter the mass spectrometer, and their signal decreases to zero. Thus, in a barrier voltage scan, mass spectrometric signals of ions sequentially disappear. Differentiation of these decreasing ion signal curves produces peaks from which an ion mobility spectrum can be reconstructed. Blocking voltages, i.e., the positions of the peaks on the barrier voltage scale are directly related to the mobility of these ions. An internal calibration using ions with known mobility values helps determine the unknown ion mobilities and allows calculation of ionic cross sections.