改进的基于二维主分量分析的掌纹识别

主分量分析(PCA)是一种在众多生物特征识别中获得成功应用的特征提取技术,是一种基于二阶统计的在最小均方误差意义上的最优维数据压缩技术,它所提取的各特征分量之间是互不相关的。传统的PCA变换是对图像向量的分析,但向量维数一般都很高。二维主分量分析方法是最近兴起的针对图像矩阵的主分量分析方法,与一维主分量分析相比能更精确的计算原始数据的协方差矩阵。将其应用于掌纹识别,并在主分量的选取上加以改进,选取了更适合于分类的主分量。实验结果表明,该方法不仅有更高的识别率,而且维数更低。     

基于主成分分析的自组织竞争神经网络在多光谱遥感影像分类中的应用

多光谱遥感影像具有波段多、信息量大的特点,传统的分类方法难以达到提高精度的要求.利用主成分分析对多波段遥感图像进行降维,再采用竞争型自组织神经网络对图像进行非监督分类.这种方法的分类精度为87.5%,Kappa系数为0.86,明显高于最大似然法,最小距离法和基于像元的自组织竞争神经网络法.实验结果表明该方法在多光谱遥感影像分类中具有较好的适用性.     

Electric Microfield Distributions in Dense One‐ and Two‐Component Plasmas

The electric microfield distributions have been calculated using an integral‐equation method for one‐component plasmas proposed by Iglesias [1] and the coupling‐parameter integration technique for two‐component plasmas proposed by Ortner et al. [2]. Electric microfield distributions are studied in the frame of the Kelbg pseudopotential model, taking into account quantum‐mechanical effects (diffraction, quantum symmetry effects) and screening effects. The screened pseudopotential is represented in a numerically approximated form. The results are compared with simulation results obtained by other authors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Improving the Robustness of Particle Size Analysis by Multivariate Statistical Process Control

The robustness of online particle size analysis in wet processes is improved by applying data based modeling methods to the control of the sample preparation and measurement sequence of the particle size analyzer. The aim is to find a more accurate and reliable method of determining the end of the particle size integration period using multivariate statistical process control (MSPC). The studied approach is tested on analyzers installed at two mineral processing plant sites and validated using two validation tests. Research shows that the proposed method works with two very different slurry types. The main advantage of the adapted approach is that there are no adjustable parameters that have to be set by the user.     

Automatic alignment of individual peaks in large high-resolution spectral data sets

Pattern recognition techniques are effective tools for reducing the information contained in large spectral data sets to a much smaller number of significant features which can then be used to make interpretations about the chemical or biochemical system under study. Often the effectiveness of such approaches is impeded by experimental and instrument induced variations in the position, phase, and line width of the spectral peaks. Although characterizing the cause and magnitude of these fluctuations could be important in its own right (pH-induced NMR chemical shift changes, for example) in general they obscure the process of pattern discovery. One major area of application is the use of large databases of (1)H NMR spectra of biofluids such as urine for investigating perturbations in metabolic profiles caused by drugs or disease, a process now termed metabonomics. Frequency shifts of individual peaks are the dominant source of such unwanted variations in this type of data. In this paper, an automatic procedure for aligning the individual peaks in the data set is described and evaluated. The proposed method will be vital for the efficient and automatic analysis of large metabonomic data sets and should also be applicable to other types of data.     

Optical Spectra of Residual Porous Silicon

The spectra of absorption (), reflection (R), ₂, and E ²₂ of residual silicon (r-Si) were calculated using the R spectra of porous silicon in the range from 0 to 20 eV and with ₂(E) in the range 2.5–5.0 eV of porous silicon specimens with P = 0.57, 0.66, and 0.77. The ₂ spectra of r-Si were decomposed into elemental components. We calculated their main parameters: the energies of maxima E _i and halfwidths H _i of bands, their areas S _i , and heights I _i , and oscillator strengths f _i . The two-phase Bruggeman model of effective dielectric function and Kramers–Kronig analysis were applied in the calculations. The essential differences between the optical spectra of the residual and cubic silicon were established. They are at least partially attributed to the quantum dimensional effects. The data obtained are compared with the known theoretical spectra of silicon clusters.     

Immobilizing a single pybox ligand onto a library of solid supports

Chiral pyridinebis(oxazoline) (pybox) ligands can be efficiently immobilized onto silica through position 4 of the pyridine ring. The crucial intermediate in this strategy is 4-chloropybox, which is prepared in good yield from chelidamic acid. 4-Chloropybox reacts with p-hydroxybenzaldehyde and p-aminophenol to give two intermediates (pybox-CHO and pybox-NH2) that allow to introduce the formyl and amino groups able to link to spacers with triethoxysilyl groups. The modified ligands and their ruthenium complexes are immobilized by grafting onto preformed silicas or, alternatively, the support is created by sol-gel synthesis using the functionalized chiral ligand as a silica monomer. In this way it is possible to create a library where the variation involves the support rather than the catalyst. The aim of this approach is to study the influence of different parameters, such as the textural properties of the support and the immobilization method, on the functionalization and catalytic performance. Some of the immobilized complexes are compared as heterogeneous catalysts in the cyclopropanation reaction of styrene with ethyl diazoacetate.     

Comments on the design of chemical libraries for screening

Different representations of molecules, based ondistinct sets of properties can yield differentperspectives of the issues involved in library design.In particular, different chemical representations cangive rise to very different estimates of requiredlibrary sizes. We provide a preliminary mathematicalframework that examines the size of libraries requiredto adequately sample the spaces corresponding to somecommonly used property sets. Introduction ofconformational flexibility is also discussed as ameans of increasing coverage of chemical libraries,while at the same time considering the thermodynamicconsequences of flexibility upon detectable activity.Our theoretical analysis reveals that the propertyspaces currently in use are extremely large andunlikely to provide adequate discrimination amongcompounds.     

暂态电化学多组份气体传感器研究Ⅱ.电势脉冲调制型气体传感器

使用微电极并融合计算机控制的快速电势调制技术,推出了一类全新的暂态电化学多组份气体传感器--"电势脉冲调制型气体传感器”.与常规的稳态电化学气体传感器比较,优化了传感器性能,拓展了传感器新的功能和功能集成化.