共查询到17条相似文献,搜索用时 109 毫秒
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提出了化学信号近似四阶导数计算的新方法——小波卷积法。该法通过信号与二阶样条小波函数的卷积运算对信号求导,能用于高噪音信号的直接求导,避免了普通导数运算将噪音放大的缺陷,即使对信噪比低至0.5的信号也能得到光滑的导数信号。详细讨论了尺度值、噪音、信号类型对求导的影响并建立了参数确定规则。将该法用于含噪音重叠分析化学信号的求导,能同时提高信号的分辨率和信噪比,结果满意。 相似文献
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电化学噪音(Electrochemical Noise,ECN)测量可用于在无电信号扰动条件下检测腐蚀体系的暂态行为,获得有关腐蚀类型和腐蚀速率的信息.小波分析不需要对ECN作稳态假设,并同时具有时间分辨和频率分辨的特点,在ECN信号处理中表现出一定的优势.本工作考察了氯离子对钢筋在模拟混凝土孔溶液中电化学噪音的影响,并采用离散小波变换(DWT)及能量分布图(EDP)分析ECN信号的时间~频率特征.结果表明,在含NaCl0.0001mol/L的饱和Ca(OH)2溶液中,时间常数为16~32s的暂态占优势;在Cl-浓度更高的溶液中,去钝化趋势为主导事件,表明钢筋在SPS溶液中活化/钝化的临界Cl-浓度介于10-4~10-3mol/L. 相似文献
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针对基于二进小波变换奇异性检测方法的不足,提出基于连续小波变换奇异性检测方法,该方法具有较细致的局部奇异性刻画能力,能够对滴定曲线的滴定终点进行精确的定位。将这种方法应用于NaOH对HCl和H3PO4滴定曲线滴定终点的确定,取得了理想的结果。 相似文献
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小波变换用于高效液相色谱的噪声滤除 总被引:13,自引:3,他引:10
根据小波变换将信号分频的性质,用Haar小波成功地解决了高效液相色谱中噪音的扣除问题,并应用于乳酸-稀土络合物体系的色谱数据,得到的色谱曲线平滑且峰位置不变,大葱旁氡群徒档土思觳庀蕖? 相似文献
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将提升haar小波变换应用于对不同类型含高噪声化学信号的处理,提出1种用于高噪声化学信号中滤除噪声的快速新方法——提升小波滤噪法,并使之与重叠峰分辨技术联用;以优选的小波分解层数对低信噪比的分析化学信号进行基于提升格式的小波变换处理,取得满意的结果;方法简单、快捷、准确、易行.运算速度是传统小波变换的一半,对高噪声化学信号的处理结果信噪比提高几百倍,峰位置相对误差小于1.5%;应用于氨基酸体系毛细管电泳检测信号的处理,有效降低了实验噪声的影响,分辨提取了难以察觉的信号.结果峰形变窄,峰高增加.大大提高了峰的分辨率.验证和显示了方法的可行性和优越性。 相似文献
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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。 相似文献
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毛细管电泳激光诱导荧光检测信号的小波滤噪 总被引:3,自引:0,他引:3
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。 相似文献
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微流控电泳芯片中化学发光信号的分段门限小波降噪 总被引:2,自引:0,他引:2
采用分段门限小波降噪(STWD)方法对化学信号中的异方差噪声进行降噪处理.用STWD法和统一门限小波降噪法同时处理两种模拟信号(其中之一包含异方差噪声).结果显示,优化参数的STWD法能够更有效地提高降噪效果.采用STWD法对微流控芯片化学发光检测信号中的异方差噪声进行处理,取得了满意的降噪效果. 相似文献
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A signals ratio method combined with wavelet transform was proposed for the resolution of a weak voltammetric signal overlapped by other components. The signals ratio method usually suffers from interference from noise and baseline contained in the original signals because these factors cause distortion of the signals ratio. The multiresolution capability of the wavelet transform method was exploited here to simultaneously remove or reduce the noise and background. As a result, a deformation-free signals ratio with good signal-to-noise ratio (SNR) was obtained even for very noisy signals. The properties of the proposed method were compared to other resolution methods. It was demonstrated that the combined signals ratio wavelet transform method was particularly applicable to resolve a minor component in the presence of large amount of other components, suggesting that it can provide improved detection limits and quantified results for minor components. The method was employed for the voltammetric determination of residual chlorine in the presence of N,N-diethyl-p-phenylenediamine (DPD). 相似文献
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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. 相似文献
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A partial least squares (PLS) and wavelet transform hybrid model are proposed to analyze the carbon content of coal by using laser-induced breakdown spectroscopy (LIBS). The hybrid model is composed of two steps of wavelet analysis procedures, which include environmental denoising and background noise reduction, to pretreat the LIBS spectrum. The processed wavelet coefficients, which contain the discrete line information of the spectra, were taken as inputs for the PLS model for calibration and prediction of carbon element. A higher signal-to-noise ratio of carbon line was obtained after environmental denoising, and the best decomposition level was determined after background noise reduction. The hybrid model resulted in a significant improvement over the conventional PLS method under different ambient environments, which include air, argon, and helium. The average relative error of carbon decreased from 2.74 to 1.67% under an ambient helium environment, which indicated a significantly improved accuracy in the measurement of carbon in coal. The best results obtained under an ambient helium environment could be partly attributed to the smallest interference by noise after wavelet denoising. A similar improvement was observed in ambient air and argon environments, thereby proving the applicability of the hybrid model under different experimental conditions. 相似文献
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《Electrochemistry communications》1999,1(7):266-270
Wavelet transforms are presented as a useful tool to analyse electrochemical noise data. Various concepts developed in the framework of wavelet transforms have been adapted to study electrochemical noise measurements. The most relevant feature of this method of analysis is its capability of decomposing electrochemical noise records into different sets of wavelet coefficients, which contain information about corrosion events occurring at a determined time-scale. Thus, this mathematical approach could become an alternative tool which solves the limitations of other more established procedures for the analysis of electrochemical noise data, such as statistical or Fourier transform-based methods. 相似文献
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A novel method to calculate the approximate derivative photoacoustic spectrum using continuous wavelet transform 总被引:1,自引:0,他引:1
A novel method based on continuous wavelet transform (CWT) using Haar wavelet function for approximate derivative calculation of analytical signals is proposed and successfully used in processing the photoacoustic signal. An approximate nth derivative of an analytical signal can be obtained by applying n times of the wavelet transform to the signal. The results obtained from four other different methods--the conventional numerical differentiation, the Fourier transform method, the Savitzky-Golay method, and the discrete wavelet transform (DWT) method--were compared with the proposed CWT method; it was demonstrated that all the results are almost the same for signals without noise, but the proposed CWT method is superior to the former four methods for noisy signals. The approximate first and second derivative of the photoacoustic spectrum of Pr(Gly)3Cl3.3H2O and PrCl3.6H2O were obtained using the proposed CWT method; the results are satisfactory. 相似文献
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The aim of this work was construction of the new wavelet function and verification that a continuous wavelet transform with a specially defined dedicated mother wavelet is a useful tool for precise detection of end-point in a potentiometric titration. The proposed algorithm does not require any initial information about the nature or the type of analyte and/or the shape of the titration curve. The signal imperfection, as well as random noise or spikes has no influence on the operation of the procedure.The optimization of the new algorithm was done using simulated curves and next experimental data were considered. In the case of well-shaped and noise-free titration data, the proposed method gives the same accuracy and precision as commonly used algorithms. But, in the case of noisy or badly shaped curves, the presented approach works good (relative error mainly below 2% and coefficients of variability below 5%) while traditional procedures fail. Therefore, the proposed algorithm may be useful in interpretation of the experimental data and also in automation of the typical titration analysis, specially in the case when random noise interfere with analytical signal. 相似文献