Search

This article uses atomic fluorescence spectroscopy (AFS) and inductively coupled plasma mass spectrometry (ICP-MS) to determine arsenic in groundwater respectively. The AFS and ICP-MS methods have good homogeneity. Samples with different concentrations of groundwater were detected using both methods, and the samples were spiked into three different concentrations to calculate their recovery rates. The results show that both methods are within the reasonable range specified by the groundwater detection standards. The blind sample detection test shows that both methods have good precision and accuracy. In contrast, the pre-treatment process of AFS method is relatively complex, with more reagents prepared in the early stage. ICP-MS method is superior to AFS method in terms of correlation linearity, instrument precision and accuracy. When detecting arsenic in groundwater, ICP-MS method can use the collision mode of helium gas and the internal standard correction of Ge72, thus reducing the matrix interference of the sample and the mass spectrometry interference during the detection process, and increasing the accuracy of the detection results. At the same time, ICP-MS method has the advantages of easy operation, stabler instrument state, and more efficiency, and so is more suitable for the detection of large-scale groundwater samples and worthy of widespread promotion and application. [ABSTRACT FROM AUTHOR]

Using plane-wave ultrasoft pseudopotential method based on first-principles density functional theory (DFT), the adsorption of Cs atom on As-rich GaAs(001) β 2 (2 × 4) reconstruction phase and Ga-rich GaAs(001)(4 × 2) reconstruction phase are investigated. The adsorption energy, work function, dipole moment, ionicity, band structure and density of state (DOS) of Cs adsorbed GaAs β 2 (2 × 4) and (4 × 2) models are calculated. The stability and electronic structure of Cs adsorbed GaAs β 2 (2 × 4) and (4 × 2) models are compared. Result shows that β 2 (2 × 4) phase is stable than the (4 × 2) phase and after that Cs adsorption β 2 (2 × 4) phase is more beneficial for photoemission. [ABSTRACT FROM AUTHOR]

Does the supply of shares affect stock price? It is an important problem not only for investors but also for the financial regulators. Stock supply could affect stock price only when there was a downward-sloping demand curves theoretically. Therefore, an empirical test on the elasticity of stock demand curves is necessary. Based on the institutional bidding data in detail during period of IPO book building, our research shows that demand curve is downward-sloping both on primary market and secondary market, which means that supply of shares will have an effect on the stock price. Therefore, the supply and demand of shares should be taken into account when financial regulators making policies and investors making investment decisions. [ABSTRACT FROM AUTHOR]

A nonparametric computationally efficient algorithm is proposed for micro-Doppler frequency estimation, assuming that this non-linear micro-Doppler frequency is approximate linear frequency in short-time intervals. In this algorithm, we use Radon-Wigner transform in short-time intervals to estimate micro-Doppler frequency. Simulation results confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]