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1.
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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NMR and LC-MS combined with an incompleted separation strategy were proposed to the simultaneous structure identification of natural products in crude extracts, and a novel method termed as NMR/LC-MS parallel dynamic spectroscopy (NMR/LC-MS PDS) was developed to discover the intrinsic correlation between retention time (Rt), mass/charge (m/z) and chemical shift (δ) data of the same constituent from mixture spectra by the co-analysis of parallelly visualized multispectroscopic datasets from LC-MS and 1H NMR. The extracted ion chromatogram (XIC) and 1H NMR signals deriving from the same individual constituent were correlated through fraction ranges and intensity changing profiles in NMR/LC-MS PDS spectrum due to the signal amplitude co-variation resulted from the concentration variation of constituents in a series of incompletely separated fractions. NMR/LC-MS PDS was applied to identify 12 constituents in an active herbal extract including flavonol glycosides, which was separated into a series of fractions by flash column chromatography. The complementary spectral information of the same individual constituent in the crude extract was discovered simultaneously from mixture spectra. Especially, two groups of co-eluted isomers were identified successfully. The results demonstrated that NMR/LC-MS PDS combined with the incompleted separation strategy achieved the similar function of on-line LC-NMR-MS analysis in off-line mode and had the potential for simplifying and accelerating the analytical routes for structure identification of constituents in herbs or their active extracts. 相似文献
3.
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· 3 H2O and PrCl3· 6 H2O were obtained using the proposed CWT method; the results are satisfactory.
Received: 21 December 1999 / Revised: 28 February 2000 / Accepted: 7 March 2000 相似文献
4.
Spectral signals are often corrupted by noise during their acquisition and transmission. Signal processing refers to a variety of operations that can be carried out on measurements in order to enhance the quality of information. In this sense, signal denoising is used to reduce noise distortions while keeping alterations of the important signal features to a minimum. The minimization of noise is a highly critical task since, in many cases, there is no prior knowledge of the signal or of the noise. In the context of denoising, wavelet transformation has become a valuable tool. The present paper proposes a noise reduction technique for suppressing noise in laser-induced breakdown spectroscopy (LIBS) signals using wavelet transform. An extension of the Donoho's scheme, which uses a redundant form of wavelet transformation and an adaptive threshold estimation method, is suggested. Capabilities and results achieved on denoising processes of artificial signals and actual spectroscopic data, both corrupted by noise with changing intensities, are presented. In order to better consolidate the gains so far achieved by the proposed strategy, a comparison with alternative approaches, as well as with traditional techniques, is also made. 相似文献
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It is often desirable to selectively remove corrupting or uninteresting signals from complex NMR spectra without disturbing overlapping or nearby signals. For biofluids in particular, removal of solvent and urea signals is important for retaining quantitative accuracy in NMR‐based metabonomics. This article presents a novel algorithm for efficient filtering of unwanted signals using the filter diagonalization method (FDM). Unwanted signals are modeled in the time domain using FDM. This modeled signal is subtracted from the original free induction decay. The resulting corrected signal is then processed using established workflow. The algorithm is found to be reliable and fast. By eliminating large, broad, uninteresting signals, many spectra can be subjected to fully automated absolute value processing, allowing objective preparation of spectra for pattern recognition analysis. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
7.
Peng J Peng S Jiang A Tan J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(4):1315-1320
A calibration transfer method for near-infrared (NIR) spectra based on spectral regression is proposed. Spectral regression method can reveal low dimensional manifold structure in high dimensional spectroscopic data and is suitable to transfer the NIR spectra of different instruments. A comparative study of the proposed method and piecewise direct standardization (PDS) for standardization on two benchmark NIR data sets is presented. Experimental results show that spectral regression method outperforms PDS and is quite competitive with PDS with background correction. When the standardization subset has sufficient samples, spectral regression method exhibits excellent performance. 相似文献
8.
The gas-phase reaction between HOSO and NO(2) was examined using density functional theory. Geometry optimizations and frequency computations were performed at the B3LYP/6-311++G(2df,2pd) level of theory for all minimum species and transition states. The ground-state potential energy surface, including activation energies and enthalpies, were calculated using the ab initio CBS-QB3 composite method. The results suggest that the addition of HOSO and NO(2) leads to two possible intermediates, HOS(O)NO(2) and HOS(O)ONO, without any energy barrier. The HOS(O)NO(2) easily decomposes into HONO + SO(2) through the low energy product complex HONO···SO(2), whereas the HOS(O)ONO dissociates to HOSO(2) + NO products. This latter dissociation is preferred from the isomerization of the HOS(O)ONO to HOS(NO)O(2). Also, HOS(O)NO(2) isomerization to HOS(O)ONO is hindered due to the presence of a large energy barrier. From the thermodynamic aspect, the main products in the title reaction are HONO + SO(2), whereas HOSO(2) + NO are expected as a minor products. 相似文献
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This article develops a Bayesian method for fault detection and isolation using a sparse reconstruction framework. The normal/training data is assumed to follow a signal‐plus‐noise model, and an indicator matrix is used to show whether the test data is from a faulty process. The distribution of the indicator matrix is modeled by a Laplacian distribution, which forces the indicator matrix to be a sparse one, and a Gibbs sampler is derived to obtain the estimation/reconstruction of the indicator matrix, the unobserved signals, and other parameters like signal mean, covariance, and noise variance. The faulty variables can then be detected and isolated by inspecting whether corresponding rows of the indicator matrix are zero. The proposed Bayesian approach is data driven; it allows for simultaneous fault detection and isolation. A simulation study and an industrial case study are used to test the performance of the proposed method. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Calibration model transfer for near-infrared spectra based on canonical correlation analysis 总被引:1,自引:0,他引:1
In order to solve the calibration transformation problem in near-infrared (NIR) spectroscopy, a method based on canonical correlation analysis (CCA) for calibration model transfer is developed in this work. Two real NIR data sets were tested. A comparative study between the proposed method and piecewise direct standardization (PDS) was conducted. It is shown that the transfer results obtained with the proposed method based on CCA were better than those obtained by PDS when the subset had sufficient samples. 相似文献
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免疫-遗传算法用于混合物重叠核磁共振信号解析 总被引:5,自引:0,他引:5
通过对免疫系统中抗体对外来抗原的识别、消除等过程的模拟,建立了一种新型的免疫算法模型.将标样信号作为抗体,混合物重叠信号作为抗原输入免疫算法模型,通过迭代运算,从抗原中消除抗体所表示的信息,当抗原被抗体完全消除时,即实现了混合物重叠信号的解析.对多组分混合氨基酸NMR谱图的解析结果证明,该算法可方便地用于多组分重叠信号的解析,为利用数据库解析混合物或生物大分子等物质的复杂NMR谱图开辟了一条全新的途径. 相似文献
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With the aim of carrying out a calibration transfer for routine analysis, partial least squares (PLS) regression was successfully applied to simultaneously determine thallium and lead by stripping voltammetry when an interfering background current is present. The presence of a significant blank signal that overlaps the thallium peak, together with the overlapping thallium and lead signals were both suitably modelled by this multivariate regression technique. Moreover, once the PLS models are built, the piecewise direct standardization (PDS) method can be used to transfer these models over time in such a way that the number of calibration samples that will be needed in future determinations is reduced from 25 to 9, without a loss of quality in the analyses. The mean of the relative errors (in absolute values) obtained for thallium and lead is below 4.94% and 3.19%, respectively. 相似文献
16.
A method based on stochastic resonance for the detection of weak analytical signal 总被引:10,自引:0,他引:10
An effective method for detection of weak analytical signals with strong noise background is proposed based on the theory of stochastic resonance (SR). Compared with the conventional SR-based algorithms, the proposed algorithm is simplified by changing only one parameter to realize the weak signal detection. Simulation studies revealed that the method performs well in detection of analytical signals in very high level of noise background and is suitable for detecting signals with the different noise level by changing the parameter. Applications of the method to experimental weak signals of X-ray diffraction and Raman spectrum are also investigated. It is found that reliable results can be obtained. 相似文献
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Equations between the differential order and the maximum of the fractional-order differential for the specified peak signals are developed based on the variation of the maximum of the specified peak signals at different orders. Also, equations between the differential order and the zero-crossing of the fractional-order differential of the specified peak signals are proposed according to the variation of the zero-crossing of the specified peak signals at different orders. Characteristic paramters of the Gaus- sian peak, Lorentzian peak, and Tsallis peak can be estimated using estimator I and estimator II which are obtained by the equations above. As a result, a new method is presented to resolve the overlapped peaks signal. Firstly, a fractional-order differential of the specified peak signals is obtained with the fractional-order differentiation filter. Then, characteristic paramters of the specified peak signals can be extracted using estimator I and estimator II. Finally, the Tsallis peak is used as a model to assign the overlapping peak signals correctly. Experimental results show that the proposed method is efficient and effective for the simulated overlapping peaks and detected overlapping voltammetric peak signals. 相似文献
19.
Jiaqi Ding Haoliang Xiao Xiaolong Huang Yujia Zou Zhimin Ye Songlin Wang Pengchao Xie Yongsheng Chen Jun Ma 《中国化学快报》2023,34(10):108316-136
Na Cl O has been widely used to restore membrane flux in practical membrane cleaning processes, which would induce the formation of toxic halogenated byproducts. In this study, we proposed a novel heatactivated peroxydisulfate(heat/PDS) process to clean the membrane fouling derived from humic acid(HA). The results show that the combination of heat and PDS can achieve almost 100% recovery of permeate flux after soaking the HA-fouled membrane in 1 mmol/L PDS solution at 50 °C for 2 h, which is att... 相似文献
20.
The energy separation between the ground-state structures of HSO and HOS has been determined by using two independent ab initio methods. In the first method, the optimized geometry of all species was obtained at the HF/6-31G(d) level, as were harmonic vibrational frequencies for zero-point energy corrections. The energies were calculated by using fourth-order Moller-Plesset perturbation theory and a 6-31G(d,p) basis set. After corrections for extrapolation of the Moller-Plesset series to infinite order and extension of the basis set to include diffuse sp-, extra d-, and f-type Gaussian functions, the predicted energy separation, including zero-point vibrational effects, is 2.5 kcal/mol. HOS is the more stable isomer. The second method uses a double-zeta basis augmented with an extra set of p functions and two sets of d functions on the sulfur and oxygen atoms and a double-zeta + p basis on hydrogen. With this basis, equilibrium structures of HSO and HOS were obtained from MCSCF calculations; the energy separation between these structures was corrected by using large scale configuration interaction. In good agreement with the first method, HOS is the more stable isomer by 3.1 kcal/mol. Through calculation of the energy change in the reaction HO2 + XY --> O2 + HXY, the first method predicts the heats of formation of HXY = HSO, HOS, and HS2 to be -0.4, -2.9, and 26.7 kcal/mol, respectively. 相似文献