Solid-state NMR and 2,3-dicyano-5,7-dimethyl-6H-1,4-diazepine

Crystalline 2,3-dicyano-5,7-dimethyl-6H-1,4-diazepine (A) was investigated by solid-state NMR spectroscopy, X-ray diffraction, and spectral simulations. The solid-state ¹³C NMR spectra of A display peculiar splittings for the methyl and cyano resonances. The crystal structure of A indicates that the methyl doublet is a consequence of two crystallographically inequivalent environments. The methyl motions associated with each site was examined via spin-lattice relaxation time (T₁) measurements, and the carbon relaxation times (T₁^C) were used to calculate energy barriers to methyl rotation. The energy barriers to rotation were then used to correlate each methyl ¹³C shift with a particular crystallographic environment. The complex cyano splittings, however, are a result of both crystallographic inequivalence and residual ¹³C–¹⁴N dipolar coupling. The multiplet patterns of the isotropic shifts (centerbands) are dependent upon the magic-angle spinning (MAS) rate. Spectral simulations, using the perturbation method, of the centerbands and first-order sidebands were used to demonstrate, and elucidate, the observed MAS rate-dependent multiplet patterns of the cyano signals.     

Effects of zero-filling and apodization on spectral integrals in discrete Fourier-transform spectroscopy of noisy data

The influence of noise on the standard deviation of spectral integrals is examined. Calculations assuming discrete Fourier-transform data are compared with Monte-Carlo simulations. The effects of zero-filling and apodization are examined for free-induction-decay (FID) signals and for symmetric spin-echo signals in one and two dimensions, with particular attention to features not previously presented in the literature. Findings suggest that for mild apodization, the known sensitivity enhancement due to zero-filling in either the real or the imaginary part signal [E. Bartholdi, R.R. Ernst, Fourier spectroscopy and the causality principle, J. Magn. Reson., 11 (1973) 9-19] is maintained; however, for stronger apodization filters, this enhancement can be obliterated completely. It is shown that results obtained by analysis of one-dimensional signals can be readily applied to multi-dimensional data. Furthermore, zero-filling has a negligible effect for symmetric spin-echo signals with implications for signal averaging in magnetic resonance imaging and spectroscopic imaging.     

psBCK-代数的Boolean滤子与psMV-滤子

在psBCK-代数中引入Boolean滤子和psMV-滤子的概念,研究了这2种滤子的性质及其相互关系．同时,借助psMV-滤子概念,给出psBCK-代数成为psMV-代数的若干充要条件．     

G -函数与迭代阵谱半径的估计

该文应用G -函数概念, 获得了迭代矩阵谱半径新的上、下界, 所得结果推广和改进了文献[1--6]中的相应结果.这些结果适合于更广泛的矩阵类, 数值结果也表明在相同的条件下这些新界优于文献[1--6]中的界.     

温度和加热时间对大气环境中纯铁光谱发射率的影响

纯铁的光谱发射率受温度的影响很大,尤其是在大气环境中,由于温度升高加剧了表面的氧化,导致其光谱发射率发生了“无规律”变化。基于基尔霍夫定理,利用研制的反射法光谱发射率测量装置对纯铁1.55μm波长的光谱发射率进行了系统的研究,探讨了温度、加热时间等因素对纯铁光谱发射率的影响。研究结果表明：纯铁的光谱发射率随着温度的升高而增大,并且在一定的温度下出现了峰值和谷值,通过分析有氧化层时金属的发射率模型,解释了这种现象的发生。恒温长时间测量结果表明,在不同的温度下,加热时间对光谱发射率的影响不同。研究结果将进一步丰富纯铁的光谱发射率数据,并为其光谱发射率在大气环境中的应用提供了实验依据。     

基于连续光谱分析的在线水质检测信号处理研究

在线光谱水质检测仪器是现代水资源环境监测技术的重要发展方向之一,具有多参数监测和准确度高、重复性好的技术优势,然在线被测水样的光谱信号处理是其关键核心技术,为此,基于连续光谱分析,建立了在线被测水样光谱测量信号的数学模型,提出了基于双波长光强比值不变性的光谱测量信号系统误差处理方法,并结合小波多分辨率滤波噪声处理技术,系统研究了基于在线被测水质参数光谱特征的背景干扰处理方法。以上信号处理方法应用于自主研制的多参数光谱水质监测仪器,在线检测标准环境水样及实际环境水样中的化学需氧量、六价铬和阴离子表面活性剂等水质参数,并与国家标准分析方法展开了现场对比测试,仪器的关键参数重复性(相对标准偏差RSD≤10%)与准确度(实际水样比对试验相对误差A≤10%)均达到并优于国家环境保护技术标准要求,表明该信号处理方法能够有效消除在线水质检测光谱测量信号的系统误差及噪声与背景干扰,对于提升光谱水质监测仪器的技术性能具有重要的作用。     

激光诱导击穿空气等离子体光谱及半经验理论模拟

利用Nd∶YAG激光器输出的1 064 nm激光进行了激光诱导击穿空气光谱实验,测量了空气等离子体的时间分辨光谱。基于局域热动力学平衡模型,建立了模拟激光诱导击穿光谱的方法。对700~900 nm波段的空气等离子体光谱进行了模拟。通过模拟结果与实验结果的比较,进一步估算出了空气中氮、氧和氩的相对含量。     

基于HSI高光谱和TM图像的土地盐渍化信息提取方法

选择黄河三角洲垦利县代表性盐碱化区域为研究区,以2011年3月15日HJ-1A卫星HSI高光谱影像和2011年3月22日TM影像为信息源,经几何纠正、图像裁剪、大气校正等预处理,分析不同盐渍化程度土地、水体、滩涂等主要地类的光谱特征,确定地类信息提取特征波段。结合土壤盐分含量,采用定量与定性相结合规则,构建地类信息提取模型,以决策树分类方法进行图像分类,提取土地盐渍化信息。利用地表点位土壤含盐量数据对地表土地盐渍化程度的化学分析结果,对遥感解译数据进行精度验证,并对高光谱和多光谱影像的分类精度进行比较分析。结果表明：HSI图像的总体分类精度达96.43%,Kappa系数为95.59%,而TM图像的总体分类精度为89.17%,Kappa系数为86.74%,说明相比多光谱TM数据,基于高光谱图像可以更为准确有效地提取土地盐渍化信息;由分类结果图可以看出,高光谱影像土地盐渍化的区分度高于多光谱影像。该研究探索了高光谱图像土地盐渍化信息的提取技术方法,提供了不同盐渍化土地的分布比例数据,可为黄河三角洲滨海盐碱土地资源的科学利用与管理提供决策依据。     

LED蓝光泄露安全性研究

研究了LED照明器件的蓝光特性。针对我国的LED照明现状,通过测试LED照明器件的光谱成分,根据现行国内外标准GB/T 20145—2006/CIE S009/E:2002和IEC62471：2006,以及CTL-0744_2009-laser决议,分析了LED光生物安全性,给LED照明灯具制造和相关安全性标准、法律制定提供参考。LED中蓝光的辐亮度值低于100 W·m-2·Sr-1时对人眼属于无危害类型,正常使用情况下不会对人眼造成伤害,但是应该注意对特殊人群(小孩)的保护,避免长时间直视光源。灯具富蓝化也会影响人的作息规律,因此色温4 000 K以下,显色指数80的LED灯具适合在室内使用,同时还要根据不同的使用距离选择不同的参数的灯具。     

A Posteriori Error Estimation of Spectral and Spectral Element Methods for the Stokes/Darcy Coupled Problem

In this paper, we carry out an a posteriori error analysis of Legendre spectral approximations to the Stokes/Darcy coupled equations. The spectral approximations are based on a weak formulation of the coupled equations by using the Beavers-Joseph-Saffman interface condition. The main contribution of the paper consists of deriving a number of posteriori error indicators and their upper and lower bounds for the single domain case. An extension of the upper bounds to the multi-domain case in the spectral element framework is also given.