高压重复频率纳秒脉冲下电信号的测量与诊断

 为了更准确地获得重复频率纳秒脉冲下气体击穿试验参数，分析了击穿电压、放电电流的测量及影响测量结果的因素等，并介绍重复频率下气体间隙击穿的耐受时间测量方法。信号测量传感器的响应带宽、间歇性存在的电磁干扰、气体间隙被击穿时瞬态高频振荡及地电位暂态升高等因素会干扰被测信号，甚至会导致被测信号局部干扰严重。采用软阈值小波降噪法可有效减小干扰。在测得分流器方波响应的基础上，采用Wiener滤波器反卷积补偿分流器输出信号的方法来校验分流器输出，结果表明分流器输出波形满足试验要求。     

A general strategy to quantify analytes through fluorescence chromaticity and luminosity

To realize a fast, easy-operation and precise way using fluorescence probes to quantify analytes is a goal to facilitate detection, especially in situ. Herein, we are reporting an approach which can be generally employed for the differentiation and quantitation of analytes through fluorescence chromaticity and luminosity. Seven representative fluorescent probes, targeting pH, cysteine, hydrogen sulfide, hydrogen peroxide, palladium and hydrazine, were synthesized and tested. Without utilizing costly instrumentations, portable devices were employed to collect data of photographs from the fluorescence samples in responses to different analytes. Subsequently, the photographic images were digitally processed to generate calibration curves between chromaticity/luminosity verse concentrations after mapping to the CIE 1931 xyY standard color space. Good linear calibration curves and quantitative analysis of unknown samples with low errors through the spectral technology demonstrated the reliability of this method. Thus, we showed the analytical method with a simple and on-site constructible/portable device which is promising for applications in more fluorescence probes     

空间调制干涉光谱成像仪线性度测试

根据线性度分析方法,结合空间调制干涉光谱成像仪的成像原理,建立了线性度测试系统.采用太阳模拟器作为光源,通过减光片得到8个亮度等级的辐射输出,用待测仪器与光谱辐射度计分别对其进行采集,比对得到待测仪器线性度为0.81%,不确定度为2.7%.结果表明：该线性度测试方法精度较高,此方法同样适用于同类干涉光谱成像仪的线性度测试.     

The measurement of atmospheric electric fields using pole mounted electrostatic fieldmeters

A pole mounted ‘field mill’ type electrostatic fieldmeter provides a simple and practical way for measurement, and for long term continuous monitoring, of ground level atmospheric electric fields. The paper describes a number of studies of this measurement method. These show how atmospheric electric field values are derived from the response of the fieldmeter when earth bonded and its height above ground level. The response of the fieldmeter is calibrated via the linear variation of its response to voltage applied during the set up procedure. The studies confirm a linearity of fieldmeter response with height above ground.     

改进的 K/S 算法对近红外光谱模型传递影响的研究

在近红外光谱分析模型传递中,常用Kennard/Stone算法(K/S算法)来选择转换集样品。K/S算法是根据样品间光谱的欧氏距离来计算样品间差异的。为了寻求样品间差异的最佳表达方式,用K/S算法选出更有代表性的样品。文章分别用欧氏距离和马氏距离计算混胺样品的光谱差异,用PDS算法传递混胺中二甲苯胺近红外光谱分析模型,通过传递后的预测标准偏差(SEP)评价两种距离的优劣。用性质差异和光谱差异结合的方式计算样品间的差异,并与单独用光谱差异和性质差异的方式进行比较。结果表明,在PDS算法中,马氏距离选出的样品更具有代表性,性质差异和光谱差异的结合更能代表样品间的差异。     

棉籽17种氨基酸含量的NIRS定标模型构建与测定方法研究

选用氨基酸含量差异较大的多年份、多品种、多地点种植的445份棉花种子为材料,分别对其进行近红外光谱扫描。用一阶导数的数学处理(1,4,4,1)、标准正态变换和去趋势(SNV+D)最佳组合的预处理方法,结合改良的偏最小二乘法(MPLS)构建棉籽17种氨基酸成分的近红外定标模型。定标结果表明,天冬氨酸、苏氨酸、谷氨酸、甘氨酸、丙氨酸、缬氨酸、异亮氨酸、亮氨酸、苯丙氨酸、赖氨酸、组氨酸和精氨酸等12种氨基酸含量的定标模型较好,其RPDc为3.735~7.132,外部检验r2为0.910~0.979,近红外光谱分析完全可以替代化学测定;而丝氨酸、蛋氨酸、酪氨酸和脯氨酸等四种氨基酸的定标模型次之,其RP-Dc为2.205~2.814,外部检验r2为0.800~0.830,近红外分析技术虽不能完全替代化学测定的结果,但仍可用于大量样品的筛选。半胱氨酸定标方程的RPDc较小(RPDc=1.358),因此,棉籽中半胱氨酸含量不能用近红外分析方法进行检测。     

Polydimethylsiloxane-based permeation passive air sampler. Part I: Calibration constants and their relation to retention indices of the analytes

A simple and cost effective permeation passive sampler equipped with a polydimethylsiloxane (PDMS) membrane was designed for the determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air. Permeation passive samplers have significant advantages over diffusive passive samplers, including insensitivity to moisture and high face velocities of air across the surface of the sampler. Calibration constants of the sampler towards 41 analytes belonging to alkane, aromatic hydrocarbon, chlorinated hydrocarbon, ester and alcohol groups were determined. The calibration constants allowed for the determination of the permeability of PDMS towards the selected analytes. They ranged from 0.026 cm² min⁻¹ for 1,1-dichloroethylene to 0.605 cm² min⁻¹ for n-octanol. Further, the mechanism of analyte transport across PDMS membranes allowed for the calibration constants of the sampler to be estimated from the linear temperature programmed retention indices (LTPRI) of the analytes, determined using GC columns coated with pure PDMS stationary phases. Statistical analysis using Student's t test indicated that there was no significant difference at the 95% probability level between the experimentally obtained calibration constants and those estimated using LTPRI for most analyte groups studied. This correlation allows the estimation of the calibration constants of compounds not known to be present at the time of sampler deployment, which makes it possible to determine parameters like total petroleum hydrocarbons in the vapor phase.     

外标法NMR实验中化学位移的校正

推导了 NMR实验中任意条件下柱状介质所感受到的有效磁场和固有化学位移的公式 ,概括了通过单谱仪、双谱仪和魔角实验校正化学位移的方法 ,阐述了平行场和垂直场中的介质磁化率效应。     

光电光谱分析电炉钢中微量Ca

电炉炼钢工艺中对 Ca的成分有一定的要求 ,特别是微量 Ca元素的快速炉前分析。采用仪器所带原始曲线 ,现有的标样 ,以及与 ICP对照比较试样 ,成功地解决了这一 Ca的分析问题。     

分立波长型近红外光谱分析仪定标模型的优化

对于滤光片型或者二极管阵列型等采用非连续扫描方式工作的近红外光谱仪来说 ,如何快速、准确地进行定标波长的优选一直是很关键的问题 ,传统近红外定标波长的优选采用向前或者向后逐步多元线性回归方法 ,依据回归结果所给出的各个波长的t检验值进行定标波长的筛选 ,但是在实际应用中 ,被筛选掉的波长也可能是非常有用的定标波长 ,而增加波长的定标所给出的定标标准差往往会减小 ,但预测精度则不一定会提高。文章将组合数学中的组合生成算法和面向矩阵运算的计算机语言相结合运用于近红外最优回归定标波长的计算机选取 ,可以在较短的时间内完成最优波长组合的选取 ,由于最优波长组合的选取是在优选定标波长数一定的前提下进行比较而且以经回归定标分析确定定标标准差最小原则 ,所以由此得到的定标方程是稳健的。