小波傅里叶自去卷积用于示波信号中背景扣除的研究

将小波变换与博里叶自线性相结合提出的小波傅里叶自线性法用于示波计时电位信号中背景的扣除,既可以保证峰位置在处理前后不变,而且能将切口转变为切口峰并使切口峰的高度增加,同时又能使博里叶自线性操作更为简单。     

示波信号能谱的傅里叶自去卷积法

以支持电解质溶液产生的示波计时电位信号作为线性函数、去极剂本身的示波信号作为去噪函数，提出了一种傅里叶自去卷积新方法--示波信号能谱的傅里叶自去卷积法。研究了噪音和切口重叠等对去卷积结果的影响。与其他傅里叶自去卷积法相比较：该方法具有操作简单、不会引起负的帝瓣效应、不用选择去噪函数等优点。     

不同软段聚氨酯的红外光谱定量分析

以异佛尔酮二异氰酸酯(IPDI)为硬段,聚环氧丙烷醚二醇(PPG)和聚己内酯二醇(PCLD)、聚碳酸酯二醇(PCD)、聚四氢呋喃醚二醇(PTMG)为软段,通过改变软段组分及相对含量,合成了系列水性聚氨酯乳液。采用傅立叶自解卷积方法,对合成试样红外光谱的重叠谱带进行分峰处理,结果有效增强了红外谱图的表观分辨率,不仅可以辨认低含量组分的特征吸收,而且当软段含量为4%时仍可检出。采用积分面积法和峰高法进行定量计算并作线性回归分析,发现积分面积法的相关系数r大于0.95。积分面积法优于峰高法。氢键作用对定量结果有一定影响。核磁共振氢谱验证数据与定量分析结果一致。     

Wavelet transform-based Fourier deconvolution for resolving oscillographic signals

Fourier self-deconvolution is an effective means of resolving overlapped bands, but this method requires a mathematical model to yield deconvolution and it is quite sensitive to noises in unresolved bands. Wavelet transform is a technique for noise reduction and deterministic feature capturing because its time-frequency localization or scale is not the same in the entire time-frequency domain. In this work, wavelet transform-based Fourier deconvolution was proposed, in which a discrete approximation (such as A(2)) obtained from performing wavelet transform on the original data was substituted for the original data to be deconvolved and another discrete appropriate approximation (such as A(5)) was used as a lineshape function to yield deconvolution. Again, instead of the apodization function, the B-spline wavelet was used to smooth the deconvolved data to enhance the signal-to-noise ratio. As a consequence, this method does not suffer as badly as Fourier self-deconvolution from noises in the original data. Thus, resolution enhancement can be increased significantly, especially for signals with higher noise level. Furthermore, this method does not require a mathematical model to yield deconvolution; it is very convenient to deconvolve electrochemical signals.     

Fourier自去卷积示波计时电位法的研究

经典的示波计时电位法一般用ｄＥ/ｄｔＥ曲线上的切口深度进行定量测定 .由于施加于电解池的极化电流频率较高 ,使方法灵敏度和分辨率大大降低 .通过选择适当的体系、改进方法等手段可改善示波图的分辨率和提高灵敏度[13],但二者常常不能同时兼备 .Ｆｏｕｒｉｅｒ自去卷积 (ＦＳＤ)是以Ｆｏｕｒｉｅｒ变换为基础、主要用于重叠峰解析的信号处理技术[4 ].它可使信号中峰形变窄、处理后峰的位置不发生变化 .然而 ,由于线性函数和滤噪函数的选择比较困难 ,使其应用受到了限制 .本文探讨了使用小波变换所得模糊项作为线性函数的可能性 ,并将改进…     

傅里叶自解卷积红外定量分析法测定氟康唑

采用傅里叶自解卷积红外定量分析技术测定了氟康唑片剂中氟康唑,选择合适的分析峰,可排除其它成分的影响,且吸光度与氟康唑的质量分数成良好的线性关系,平均回收率为100.5%,RSD为1.5%。本方法可用于氟康唑片剂中氟康唑的测定。     

Multi‐scale Gaussian/Haar wavelet strategies coupled with sub‐window factor analysis for an accurate alignment in nontargeted metabolic profiling to enhance herbal origin discrimination capability

Metabolic dataset can provide an overview of different herbal origin, which is conducted by some statistical procedures. Such results often deviate to a certain degree, due to peaks shifts in chromatographic signals. In order to solve this problem, an improved algorithm of combining sub‐window factor analysis with the mass spectrum information is proposed. The algorithm uses a peak detection approach derived either from multi‐scale Gaussian function or Haar wavelet to locate the peaks with different application scope; the candidate drift points at each peak are estimated by Fast Fourier transform cross correlation; Specifically, the best drift points at each candidate peaks are confirmed by sub‐window factor analysis and mass spectrum information in nontargeted metabolic profiling. Finally, the peak regions were aligned against a reference chromatogram, and the non‐peak regions were used linear interpolation. The chromatographic signals of 30 Bupleurum samples were aligned as an illustration of this algorithm, and they could be well distinguished using some statistical procedures. The result demonstrates that the presented method is stronger than other mass‐spectra based algorithms, when facing the alignment of some co‐eluted peaks.     

序列结构对苯乙烯/丁二烯共聚物热释电流峰的影响

本文研究聚合方式对苯乙烯/丁二烯共聚物热释电流峰(TSC)的影响。共聚物试样有三个电流峰(β、α和ρ峰)。实验结果表明:聚合方式对β峰(丁二烯局部运动)基本没有影响,但对α峰(丁二烯相的T_g转变)的位置有明显的影响,而且两步法试样有两个α峰;嵌段共聚物试样在高温还有一肩部(苯乙烯相的T_g转变),无规共聚试样没有肩部。由共聚物的序列结构能圆满解释TSC结果,而序列结构决定于聚合方式。因此,本工作将苯乙烯/丁二烯共聚物的序列结构与性能联系起来。     

Fine-structure enhancement--assessment of a simple method to resolve overlapping bands in spectra

A simple mathematical procedure--fine-structure enhancement--has been assessed on its ability to resolve overlapping bands in spectra. Its advantages and limitations have been explored using synthetic and experimental spectra. Fine-structure enhancement involves smoothing the original spectrum, multiplying the smoothed spectrum with a weighting factor and subtracting this spectrum from the original spectrum. As a result, the fine-structure of the original spectrum is enhanced in the processed spectrum and bands that overlap in the original spectrum appear as distinct bands in the processed spectrum. To be resolved by fine-structure enhancement, Lorentzian lines have to be separated by more than their quarter width at half maximum, Gaussian lines by more than their half width at half maximum. A comparison of fine-structure enhancement and Fourier self-deconvolution shows that Fourier self-deconvolution has in theory a higher potential to resolve overlapping bands. However, this depends crucially on the correct choice of the parameters. In practice, when parameters commonly used are chosen for Fourier self-deconvolution, fine-structure enhancement leads to similar results. This is demonstrated at the example of the infrared absorbance spectrum of the protein papain, where the amide I band components could be resolved similarly with both methods. Thus, fine-structure enhancement seems to be a simple alternative to Fourier self-deconvolution that does not require specialised software.     

Temperature dependences on the infrared spectra of some proteins

Recent developments of FT-IR and computer techniques made it possible to detect minute changes (temperature dependences etc.) in the infrared spectra of proteins in aqueous solution.In this paper we studied temperature dependences of the amide I and I bands of ribonuclease A (RNase A), calmodulin (CaM), and Ca²⁺-bound CaM in H₂O and D₂O solutions between 28°C and 70°C using the difference-spectrum and Fourier self-deconvolution techniques.     

Mass Spectral Peak Distortion Due to Fourier Transform Signal Processing

Distortions of peaks can occur when one uses the standard method of signal processing of data from the Orbitrap and other FT-based methods of mass spectrometry. These distortions arise because the standard method of signal processing is not a linear process. If one adds two or more functions, such as time-dependent signals from a Fourier transform mass spectrometer and performs a linear operation on the sum, the result is the same as if the operation was performed on separate functions and the results added. If this relationship is not valid, the operation is non-linear and can produce unexpected and/or distorted results. Although the Fourier transform itself is a linear operator, the standard algorithm for processing spectra in Fourier transform-based methods include non-linear mathematical operators such that spectra processed by the standard algorithm may become distorted. The most serious consequence is that apparent abundances of the peaks in the spectrum may be incorrect. In light of these considerations, we performed theoretical modeling studies to illustrate several distortion effects that can be observed, including abundance distortions. In addition, we discuss experimental systems where these effects may manifest, including suggested systems for study that should demonstrate these peak distortions. Finally, we point to several examples in the literature where peak distortions may be rationalized by the phenomena presented here. Graphical Abstract

?     

小波变换用于示波信号中有用信息提取的研究

示波分析是近年来在我国发展起来的一个新的电化学分析研究领域［１～４］．它根据阴极射线示波器荧光屏上示波图及其变化进行分析测试,从原理上可以将其分为示波电位法和示波计时电位法;从测定方式上可以将其分为示波滴定和示波测定．关于示波电位法的一些理论问题（如...     

2nd-order spline wavelet convolution method in resolving chemical overlapped peaks

A 2nd-order spline wavelet convolution method in resolving overlapped peaks is developed. It determines the number of peaks, peak positions and width through wavelet's convolution, then uses spline function to construct the resoluter, which is used to resolve overlapped peaks. Theoretical proof is given, and the selections of wavelets and parameters are discussed. It is proven that baseline separation can be achieved after processed, the relative errors of peak position and area are less than 0.2% and 4.0% respectively. It can be directly applied to seriously overlapped signals, noisy signals and multi-component signals, and the results are satisfactory. It is a novel effective method for resolution.     

样条小波和Fourier变换联用技术在分析化学中的应用

探讨了样条小波和Fourier变换方法的算法及应用特征,将两种方法联合使用,设计出了一种新型的数字滤波器,使两种方法互相取长补短,使各自的优势能得到充分发挥.优选了处理低信噪比分析化学信号的滤波参数.不仅能使结果峰形高度保真,克服样条小波分析方法的不足,而且可对高噪声信号进行处理.     

基于积分渐进展开的气相色谱重叠峰快速解析法

论文提出用积分渐进展开解析气相色谱重叠峰,该方法有3个主要步骤：首先将谷峰或肩峰分成两个积分区域,得到一个子区域的积分方程和一个重叠峰面积的代数方程;然后用数值积分求出这两个方程计算中所需要的峰面积,再用积分渐进公式将积分方程展开成代数方程;最后,将这两个方程与峰高约束方程联立后,得到一个非线性代数方程组,用Gauss-Seidel迭代可以快速求解方程组,方程收敛的最大迭代次数不超过20次。仿真和实验结果表明,解析的峰高和峰面积误差均很小,峰面积最大误差低于6.44%,峰高的最大误差约为6.80%。由于该算法精度高,效率高,所以这个方法可以用于气相色谱重叠峰和一般色谱峰的实时在线解析。     

Anaerobic digestion of municipal solid waste and sewage sludge under mesophilic and thermophilic conditions

In this study, thermal analysis in differential scanning calorimetry associated to Fourier self-deconvolution (FSD) of infrared spectra was applied to the study of anaerobic digestion of the organic fraction of domestic solid waste and sewage sludge mixed in 1:1 ratio under mesophilic and thermophilic conditions. Curves showed an exothermic peak in the high-temperature range and a number of endothermic and/or exothermic peaks in the low- and medium-temperature range. The high-temperature exotherm was a common feature on curves of all samples. Digestates evidenced a shift of this exotherm toward higher temperature with respect to both substrates and feed-in materials as a result of a greater chemical complexity attained by organic matter (OM) during the process. A further shift toward higher temperature values was observed on digestates obtained under thermophilic conditions with respect to digestates obtained under mesophilic conditions. This result was associated to a higher recalcitrance of digestates produced under more drastic conditions. Based on evidence obtained by FSD spectra, the exotherm in the medium-temperature range was assigned to combustion of carbohydrates and to loss of aliphatic structures and carboxylic groups. Enthalpy data associated to the high-temperature exotherm were used to differentiate feed-in materials and their corresponding digestates and to distinguish digestates obtained under different operative conditions.     

连续样条小波变换用于分解重叠峰的研究

以B-样条小波为分析小波，提出了用于分析化学重叠信号解析的新方法——连续样条小波变换，结果表明：连续样条小波变换应用于分析化学信号的处理，能使峰变窄同时还能提高信号的信噪比，是一种新型有效的重叠信号解析方法，能从含噪声重叠信号中直接得到重叠峰的峰数目及其相应的峰位置。     

Study on spline wavelet self‐convolution in filtering and resolving overlapped voltammetric signals simultaneously

The normal distribution function is used as resolving factor and spline wavelet self‐convolution is used to resolve the overlapped peaks containing noise. The resolution of several kinds of overlapped peaks (SNR from 5 to 50) simulated by computer has been discussed in details. It is known that the overlapped peaks with noise can be separated (SNR > 50) directly and the noise is removed at the same time in time domain. Base‐line separation can be achieved. The relative errors of peak area and position are less than 5.0%. The satisfactory results are also obtained in resolving voltammetric overlapped signals by this method.     

A novel method to calculate the approximate derivative photoacoustic spectrum using continuous wavelet transform

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.     

Comparing different means of signal treatment for improving the detection power in HPLC-ICP-MS

The purpose of detecting trace concentrations of analytes often is hindered by occurring noise in the signal curves of analytical methods. This is also a problem when different arsenic species (inorganic As(III) and As(V) as well as organic dimethylarsinic acid and arsenobetaine) are to be determined in food and feeding stuff by HPLC-ICP-MS, which is the basis of this work. In order to improve the detection power, methods of signal treatment may be applied. We show a comparison of convolution with Gaussian distribution curves, Fourier transform, and wavelet transform. It is illustrated how to estimate decisive parameters for these techniques. All methods result in improved limits of detection. Furthermore, applying baselines and evaluating peaks thoroughly is facilitated. However, there are differences. Convolution with Gaussian distribution curves may be applied, but Fourier transform shows better results of improvement. The best of the three is wavelet transform, whereby the detection power is improved by factors of about 6.