近红外光谱判别分析滤波器的设计与应用

近红外光谱(NIRS)在定量和判别分析中已得到广泛应用,化学计量学在其中发挥了重要作用,但仍需要建立基于新原理的方法,简化数据处理和建模过程,使近红外光谱分析更加方便、更加快速.多元光学计算(M O C)技术通过设计合适的光学滤波器可以在光谱测量的同时,根据光谱的整体形状得到定性定量结果.作为一种新的测量和计算方式,近...     

Blood species identification using Near-Infrared diffuse transmitted spectra and PLS-DA method

Blood species identification is of great significance for blood supervision and wildlife investigations. The current methods used to identify the blood species are destructive. Near-Infrared spectroscopy method is known for its non-invasive properties. In this research, we combined Near-Infrared diffuse transmitted spectra and Partial Least Square Discrimination Analysis (PLS-DA) to identify three blood species, including macaque, human and mouse. Blind test and external test were used to assess the PLS-DA model. The model performed 100% accuracy in its identification between three blood species. This approach does not require a specific knowledge of biochemical features for each individual class but relies on a spectroscopic statistical differentiation of the whole components. This is the first time to demonstrate Near-Infrared diffuse transmitted spectra have the ability to identify the species of origin of blood samples. The results also support a good potential of absorption and scattering spectroscopy for species identification in practical applications for real-time detection.     

Labor market underrepresentation results in minority discrimination: A dynamic hiring model with employer learning

This paper develops a dynamic model of minority labor market discrimination. Employers repeatedly decide to hire either minority or majority job candidates whose productivities are unobservable beforehand. Hiring decisions are based on productivity expectations derived from the observable productivity of employers’ previously hired workers. If employers have fewer minority workers initially—a plausible assumption for (numerical) minorities—they discriminate against minority workers over time. Discrimination results from more dispersed minority expectations across the employer population and stronger effects of additional productivity observations on minority expectations. Both effects are a direct consequence of the minority’s initial underrepresentation in firms. I demonstrate the emergence of minority discrimination formally in a two-period hiring model and show simulation results for longer time frames.     

Improving the detection of significant factors using ANOVA-PCA by selective reduction of residual variability

Selective elimination of residual error can be used when applying Harrington's ANOVA-PCA in order to improve the capabilities of the method. ANOVA-PCA is sometimes unable to discriminate between levels of a factor when sources of high residual variability are present. In some cases this variability is not random, possesses some structure and is large enough to be responsible for the first principal components calculated by the PCA step in the ANOVA-PCA. This fact sometimes makes it impossible for the interesting variance to be in the first two PCA components. By using the proposed selective residuals elimination procedure, one may improve the ability of the method to detect significant factors as well as have an understanding of the different kinds of residual variance present in the data.Two datasets are used to show how the method is used in order to iteratively detect variance associated with the factors even when it is not initially visible. A permutation method is used to confirm that the observed significance of the factors was not accidental.     

NACE Discrimination of Black Ballpoint Pen Inks

A non-aqueous capillary electrophoresis (NACE) method was developed for analyzing seven basic dyes contained in black ballpoint pen inks. Baseline separation of the studied compounds was achieved on a 57 cm × 75 μm capillary by using a non-aqueous solution composed of 1.0% acetic acid and 60 mM ammonium acetate in methanol medium. Based on the pattern of NACE electropherograms, 120 black ballpoint pens from different manufacturers were divided into six groups in terms of dye categories. Moreover, the black ballpoint pens from the same group may be further distinguished by cluster analysis based on the content of different dyes and some unknown peaks. Our results indicated that the developed NACE method is a credible warrant for investigation of the fraudulent documents.     

Deconvolution of liquid scintillation alpha spectra of mixtures of uranium and radium isotopes

A method for the determination of uranium and radium isotopes in water samples is proposed. Liquid scintillation techniques were used for collecting alpha spectra, which were then analyzed by fitting the alpha peaks with overlapping Gaussians. The analysis can quantify the observed isotopes with accuracy depending on the activity of each isotope.In order to simulate the peaks with Gaussian normal distribution functions, the centroid of each peak as well as the full width at half maximum (FWHM) are required, as they depend on the quenching of the sample. For this purpose, samples with known activities of ²²⁶Ra and its decay products and also of the uranium isotopes ²³⁸U and ²³⁴U, at various quenching levels, were used to establish the correlation of the peaks’ shift with the quench effect. In addition, the correlation of the FWHM with the centroid of a peak was determined, using the same procedure.Following the above analysis technique, an average of 97 ± 2% of detection efficiency and a lower limit of detection of 8.2 mBq kg⁻¹ for alpha isotopes were achieved.     

基于PCA和LS-SVM的傅里叶变换近红外光谱的黄酒酒龄的鉴别模型

利用傅里叶变换近红外光谱技术,对黄酒酒龄鉴别的模型进行研究。对绍兴黄酒样本光谱主成分进行提取与分析,并发现前3个主成分具有较明显的聚类特征。其次,利用LS-SVM模型对不同主成分数进行分类和寻优,发现当主成分数为6时达到判别的正确率是100%,此时模型的两个参数γ和2σ分别为61.890和1.769。研究表明,利用傅里叶变换近红外光谱技术并结合主成分分析(PCA)和最小二乘法支持向量机(LS-SVM)可作为一种可靠、准确、快速的检测方法用于黄酒酒龄定性鉴别分析。     

平移多项式的判别序列

研究平移多项式的判别序列的性质,并给出平移多项式的正根判别序列的显式表达式.     

近红外漫反射光谱法快速无损鉴别阿胶真伪

采用近红外光谱漫反射光谱技术和模式识别技术快速鉴别阿胶真伪.收集来源不同的阿胶(真品8个,伪品6个),采集其近红外漫反射光谱,使用多重散射校正和小波变换对光谱进行预处理后,分别应用相似度匹配和马氏距离方法建立质量鉴别模型.相似度法使用真品谱图作为标准谱图,用样品谱图与标准谱图的相似度值来鉴别阿胶质量;对阿胶样品进行重复扫描得到28张谱图,随机分为3组后应用马氏距离法建立交叉验证鉴别模型.两种模式识别方法均能准确无误的鉴别阿胶真伪,表明近红外光谱和模式识别技术结合可快速、准确、客观地进行阿胶质量鉴别,可推广到其他中成药的质量鉴别.     

Discrimination of individual atoms on Ge/Si(1 1 1)-(7 × 7) intermixed surface

We have discriminated individual Ge atoms from the intermixed Ge/Si(1 1 1)-(7 × 7) surface using a non-contact atomic force microscope at a room temperature environment. In fact, Si-Ge (IV-IV) binary system is considered as one of the most difficult systems for atomic discrimination among atoms in the IV group because of the similarities in the electronic and chemical properties. However, in this study, we found one of the most attractive tools to discriminate a specific atom from the others even in the difficult Si-Ge system. Ge atoms are shown as dim spots in comparison to Si atoms with bright spots on the intermixed surface by a weak chemical bonding energy and/or a relaxation effect despite large atomic radius and high spatial position in both variable frequency shift and topographic images. The discrimination of individual atoms with respect to the chemical interaction variation will further provide a chance to manipulate different atomic species and assemble various nanostructures in near future.