Recent Achievements in Sample Introduction Systems for Use in Chemical Vapor Generation Plasma Optical Emission and Mass Spectrometry: From Macro- to Microanalytics

Abstract

Chemical vapor generation (CVG) offers several significant advantages for analyses, including efficient matrix separation, which often leads to a reduction of interferences and better detection limits; high transport efficiency of analyte into the atomic spectroscopic detector; in some cases, high selectivity to permit differentiation of chemical species of a particular element and enable use of gas-phase separation methods for speciation of some elements.

The development of CVG techniques from a Marsh test (arsine generation) to a recent device combining vapor generation with multichannel sample introduction systems and separation or preconcentration techniques at the macro- and microscale for use in optical emission and mass spectrometry is reviewed.     

基于航空多角度偏振辐射计遥感数据评估陆地表面偏振反射模型

运用新研制的大气多角度偏振辐射计(AMPR)获得航空遥感数据并结合实验室测量数据对常用的三种地表偏振模型进行评估,分析地表偏振反射率的波段响应和角度响应特征。实验发现偏振反射率对波段变化的响应很小,该结论得到85%以上飞行数据的气溶胶反演结果支持。实验室数据中,波长变化1nm的黄棕壤和红沙土的偏振反射率改变量仅分别为2.43×10-6和1.47×10-6。在角度响应特征上,三种模型都与实验数据符合得很好,高植被覆盖率时三种模型与实际测量数据的偏差较小。分别对三种模型的航空数据进行拟合,Nadal和Bréon(NB)开发的地表偏振反射率模型与飞行数据符合得最好,拟合偏差约是其他两个模型的一半,NB模型能够更精确地描述地表偏振反射的特性。     

Photon statistics measurement for coherent fields

An efficient scheme for photon statistics measurement is presented based on the Hanbury-Brown-Twiss configuration. We set the sampling time Ts to satisfy the relationship of Ts 〈 Td 〈 Tm, where Td is the dead time of each detector and Tm is the laser pulse repetition period. And each single photon detector cannot detect more than one photon in each pulse. The approach can sufficiently eliminate the influences of the detector＇s dead time on photon statistics. At last, the photon statistics of coherent field is experimentally determined.     

像元光敏宽度对干涉成像仪复原光谱幅值的影响

推导出了静态干涉成像光谱仪的探测器阵列采样空间调制干涉图的实际数学表达式,由此进一步推导出了含像元光敏宽度的复原光谱幅值的一般表达式。分析结果表明,当像元间距一定时,光敏宽度对复原光谱幅值存在影响。对于确定的光敏宽度,随着波数的变长,复原光谱幅值所受到的影响逐渐增大;对于确定的波数,随着光敏宽度的变宽,复原光谱幅值所受到的影响逐步增大。     

Calculation of bridge function coefficients via modified Mayer-samplings

Two modified Mayer-sampling methods are described based on Transition Matrix Monte Carlo (TMMC) and overlap sampling for calculating the integrated diagrams appearing in the coefficients of the bridge function; b_n (r) constructed in terms of the total correlation function h(r) for a hard-sphere system. Calculations are performed using prescribed h(r) for reduced densities at 0.2, 0.5 and 0.8 up to the third-order expansion in density. The results from these methods compared with the generic Monte Carlo Mayer-sampling are analysed in detail. It was found that the TMMC Mayer-sampling approach shows better precision over core and tail regions of b ₂(r) and b ₃(r), and the overlap sampling method shows overall improvement in the precision of the bridge coefficients. Both methods can be straightforwardly applied to calculate higher order bridge function coefficients and to any model systems with relatively simple modifications.     

基于AMOEBA可极化力场研究蛋白二聚化对于gramicidin A通道电导的影响

在离子通道性质的研究中,由于可极化力场计算量巨大,长期以来使用最广泛的依旧是经典力场. 本文考察了可极化力场在描述离子通道gramicidin A(gA)二聚状态下离子输运性质方面的可靠性. 利用AMOEBA可极化力场对单通道gA和双通道gA进行增强采样模拟,从电导、扩散系数和自由能等方面描述了gA二聚化对钾离子和钠离子穿越通道过程的影响. 计算结果显示,可极化力场模拟获得的钾离子和钠离子穿越通道的电导与实验数值吻合. 进一步的数据分析揭示了蛋白质二聚化影响gA通道离子输运性质的分子机制,即蛋白二聚化通过调整gA蛋白周围的环境(磷脂头基、通道外离子和体相水分子的分布)而不是直接调整gA蛋白的构象来加速钾离子和钠离子穿越通道.     

Intrinsic Dimension Estimation-Based Feature Selection and Multinomial Logistic Regression for Classification of Bearing Faults Using Compressively Sampled Vibration Signals

As failures of rolling bearings lead to major failures in rotating machines, recent vibration-based rolling bearing fault diagnosis techniques are focused on obtaining useful fault features from the huge collection of raw data. However, too many features reduce the classification accuracy and increase the computation time. This paper proposes an effective feature selection technique based on intrinsic dimension estimation of compressively sampled vibration signals. First, compressive sampling (CS) is used to get compressed measurements from the collected raw vibration signals. Then, a global dimension estimator, the geodesic minimal spanning tree (GMST), is employed to compute the minimal number of features needed to represent efficiently the compressively sampled signals. Finally, a feature selection process, combining the stochastic proximity embedding (SPE) and the neighbourhood component analysis (NCA), is used to select fewer features for bearing fault diagnosis. With regression analysis-based predictive modelling technique and the multinomial logistic regression (MLR) classifier, the selected features are assessed in two case studies of rolling bearings vibration signals under different working loads. The experimental results demonstrate that the proposed method can successfully select fewer features, with which the MLR-based trained model achieves high classification accuracy and significantly reduced computation times compared to published research.     

密闭舱内VOCs现场快速定量检测技术与装置研究

该文发展了可对压强变化的密封舱实现计量采样-富集的采样技术,基于薄壳金属筒式低功耗均温色谱柱组件,结合微池热导检测器/小型氢火焰离子化检测器,建立了一种对密闭舱内挥发性有机物(VOCs)进行现场快速定量检测的方法和装置.根据负压罐和密封舱的压强差值和绝压值以及温度,计算出有效采样体积(折算到标准大气压),进而计算出富集...     

面阵CCD信号采集系统的噪声抑制

分析了CCD输出噪声及其一般抑制方法,提出了一种基于面阵CCD信号采集系统的噪声抑制方法。设计了CCD信号采集系统的噪声抑制电路和处理电路,应用于CCD442A型面阵CCD;并使用积分球对采集系统进行辐射定标,计算得到系统的信噪比。仿真和辐射定标实验表明,该面阵CCD信号采集系统具有相关双采样和暗电平校正功能,抑制了CCD输出信号的复位噪声和暗电流噪声;在中等照度条件下,系统信噪比达到40dB。     

自适应斜Z字形采样Hadamard单像素成像

单像素成像技术在成像速度和质量上已经取得一定的进展,然而,如何在保证成像质量的前提下提升成像速度仍然是一个待解决的问题.对Hadamard系数矩阵中每条斜列上的系数绝对值求取平均值后,发现其具有迅速减小的特征,基于此发现提出了一种自适应斜Z字形采样方法,以实现预期的成像质量和速度提升.实验结果表明,该方法可以有效减少采...