Sparse Linear Algebra and Geophysical Migration: A Review of Direct and Iterative Methods

The pre-stack depth migration of reflection seismic data can be expressed, in the framework of waveform inversion, as a linear least squares problem. Together with the precise definition of this operator, we detail additional main characteristics of the forward model, like its huge size, its sparsity and the composition with convolution. It ends up with a so-called discrete ill-posed problem, whose acceptable solutions have to undergo a regularization procedure. Both direct and iterative methods have been implemented with specific attention to the convolution, and then applied to a given data set: a synthetic 2-dimensional profile of revealing size with some added noise. The efficiency with regard to computational effort and storage requirements is evaluated. The needed regularization of the solution is thoroughly studied in both cases. From the point of the global inverse problem, the extra feature of providing a solution that can be differentiated with respect to a parameter such as background velocity is also discussed.     

Decomposition of DSC curves of dairy products with Gaussian functions

Summary DSC measurements have wide application in the field of biochemical/biophysical research to look into the melting behaviour of muscle proteins in different intermediate states of ATP hydrolysis cycle as well as in the field to develop dairy products. It was a demand to develop a deconvolution program to evaluate and interpret the background of DSC scans such a way that the decomposition into a proper function has to be simple and quick. There should be possible to choose the proper parameters as well as to calculate the data of decomposing curves with the simultaneous graphic representation of them including the resultant DSC scan as the sum of decomposing functions. In most cases Gaussian function is used for this purpose. Our main field of interest is the food physics where e.g. the proliferation of different probiotic bacteria follows a lognormal distribution, its first derivative is a Gaussian one, for this reason we have chosen it. The main parts of this PC program are: -the process of fitting and calculation of Gaussian functions, a multiple step correction of these function (optimal fitting), graphic representation of all functions. An example is shown for its application how to analyse the melting of butter fat.     

Resolution of overlapped non-absorbing and absorbing solutes using either an absorption null-balance detection window or multivariate deconvolution applied to capillary electrophoresis of anionic surfactants

Non-absorbing alkyl ether sulfates (AES) can be separated using anthraquinone-2-carboxylic acid (AQCA) as a probe; however, absorbing alkyl benzene sulfonates (ABS), if present, interfere indirect detection of most AES oligomers. Overcoming of this interference, as well as the simultaneous characterisation and evaluation of AES, fatty acids and ABS, was accomplished by using a diode-array detector and the procedures here discussed. First, it was shown that ABS can be made undetectable by using a 9 nm wide and 227 nm centred charge-absorptivity null-balance detection window (NBDW), where its contribution to the absorbance cancels the dilution effects that its presence induces on the signal of the background chromophore (BGC). Two other procedures, not requiring any prior knowledge on the nature of the absorbing interference, were also addressed. In the first one, the NBDW procedure was emulated by software, by treating the time-wavelength data matrix stored during the experimental run, and in the second one, both the ABS and BGC spectra, and the concentration profiles of ABS and the non-absorbing solutes, were recovered by orthogonal projection approach (OPA) and alternating least squares (ALS). The OPA-ALS processing provided the deconvolved signals and the wavelengths required to implement the experimental and software-emulated NBDW procedures. A composite ABS spectrum and a mixed concentration profile of the non-absorbing solutes, that involves mutual ABS-BGC dilution effects are enclosed in the OPA-ALS straightforward solutions. The pure spectra and concentration profiles were finally retrieved by crossed orthogonalisation. For the NBDW procedures, the limits of detection (S/N = 3) for AES oligomers overlapped by 1500 microg ml(-1) ABS were of ca. 10 microM AES. Using decyl sulfate as internal standard, the relative standard deviation for AES in an ABS containing industrial sample was 4.5%. The procedures here described are useful to remove the interference produced by any absorbing solute when overlapped with indirectly detected solutes in both capillary electrophoresis (CE) and HPLC.     

空间变化PSF非盲去卷积图像复原法综述

传统的图像复原一般认为点扩散函数(PSF)是空间不变的,实际光学系统由于受到像差等因素的影响,并非严格的线性空间不变系统,基于空间变化PSF的非盲去卷积图像复原法逐渐体现其优越性。空间变化PSF的非盲去卷积图像复原法先准确估计图像空间变化的PSF,再利用非盲去卷积算法对图像进行复原,有利于恢复出高质量图像。本文从算法的角度综述了近几年提出的基于空间变化PSF的非盲去卷积图像复原方法,并对比了基于强边缘预测估计PSF的非盲去卷积法、基于模糊噪声图像对PSF估计非盲去卷积法等算法的优缺点,各算法分别在PSF估计精确度、振铃效应抑制效果、适用范围等方面体现出各自的优劣。空间变化PSF的非盲去卷积图像复原法的研究,有利于推进图像复原技术向更高水平发展,使光学系统往轻小型化方向发展,从而在多个科学领域发挥其重要作用。     

Computer Enhanced Spectroscopic Separation of Coeluted Components in Supercritical Fluid Chromatography Coupled with an Ultraviolet Multichannel Detector

Abstract

Computer enhanced spectroscopic separation technique has been applied to identification of coeluted components in supercritical fluid chromatography by using an ultraviolet photodiode array multichannel detector. The powerful function such as peak deconvolution procedure has successfully offered thespectroscopic complete separation for even partially or completely coeluted components in super critical fluid chromatography.     

盲图像复原研究现状

盲图像复原是在未知或不完全确知相关原始图像与成像点扩展函数的先验知识的情形下,利用所观测到的降质图像对原始图像和点扩展函数进行估计的一种图像处理方法。本文对近年来涌现出的主要盲图像复原算法进行了回顾,并根据相应的理论来源及相互联系将其划分为四大类,对各类复原算法及其改进算法进行了分析和讨论,为更清晰与深刻地认识和理解盲图像复原理论、解决实际图像降质问题提供参考。     

Comparative qualitative analysis of nonylphenol isomers by gas chromatography-mass spectrometry combined with chemometric resolution

The relationship between nonylphenol (NP) isomers' structures and their estrogenic potencies has been evaluated previously. However, due to their similarities in both chemical and physical properties, complete separation and identification remain strikingly difficult. In the present study, gas chromatography-mass spectrometry (GC-MS) is employed to separate commercial NP isomers. Both extracted ion chromatograms (EIC) based on selected ions known to be definitive for the suite of isomers, and the heuristic evolving latent projection (HELP) chemometric resolution method have been applied for the analysis and identification of the NP isomers. This method corrected the wrong identification of one isomer which was suspected based on the EIC data, and also was able to be applied for the determination of an additional isomer with low abundance. Overall, 15 NP isomers have been proposed by the HELP interpretation method. Pure component chromatograms and mass spectra have been extracted with the aid of chemometric resolution. The applicability of the commercial deconvolution software package automated mass spectral deconvolution and identification system (AMDIS) has also been tested against the HELP method for comparative presentation of pure component mass spectra.     

Qualitative drug analysis of hair extracts by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

A technique using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) is applied to a qualitative analysis of three sample extracts from hair suspected of containing various drug compounds. The samples were also subjected to a quantitative target analysis for codeine, morphine, 6-monoacetylmorphine (6-MAM), amphetamine, methamphetamine, methylenedioxyamphetamine (MDA), methylenedioxymethylamphetamine (MDMA), methadone, and benzylpiperazine (BZP) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). GC × GC/TOFMS provided a non-specific procedure that identified various drugs, metabolites, and impurities not included in the target analysis. They included cocaine, diazepam, and methaqualone (quaalude). Comprehensive GC × GC separation was achieved using twin-stage cryo-modulation to focus eluant from a DB-5ms (5% phenyl) to a BPX50 (50% phenyl) GC column. The TOF mass spectrometer provided unit mass resolution in the mass range m/z 5–1000 and rapid spectral acquisition (≤500 spectra/s). Clean mass spectra of the individual components were obtained using mass spectral deconvolution software. The ‘unknown’ components were identified by comparison with mass spectra stored in a library database.     

基于维纳滤波的迭代盲解卷积

盲解卷积是在两个卷积因子未知的情况下,通过卷积结果来获知卷积因子的。不考虑噪声,针对高斯模糊图像,在初始估计点扩展函数之后,利用维纳滤波的方法进行频域迭代盲解卷积,达到图像恢复的目的。实验表明,恢复的图像纹理比较清晰,边缘有所改善,主观视觉效果显著。该算法提高了分辨率。     

Gradient-Based Blind Deconvolution with Phase Spectral Constraints

This paper proposes a new blind deconvolution method with additional phase spectral constraints for a blurred image. A degradation of an original image is mathematically modeled by a convolution of an original image and a point-spread function (PSF). The proposed method consists of the following three steps: (i) projection onto a complex set satisfying the phase spectral constraint in a frequency space; (ii) minimization of a cost function preserving the constrained phase spectra; and (iii) projection onto an image space satisfying nonnegative and support constraints. This method restores both the original image and the PSF with high accuracy. The effectiveness of the proposed method is verified by applying it to some blind deconvolution problems for digital images, and the experimental results show that the performance is superior to the conventional blind deconvolution methods.