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Yang F.,Sichuan Agricultural University | Li J.,Nanjing University | Yang W.,Sichuan Agricultural University | Qian Y.,Xinjiang University | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

Remote sensing offers a scientific, accurate, rapid technique for predicting plant coverage, but a pixel in remote sensing image includes more information, which will affect grassland classification accuracy and the quantitative development of remote sensing techniques. In this study, Landsat Thematic Mapper (TM) data was used to discuss the key problem of mixed pixel decomposition by using spectral mixture analysis in grassland of the Northern Tianshan Mountains. Four vegetation indexes and fractions derived from spectral mixture analysis, i. e., green vegetation, dune, and saline alkali soil, were calculated and compared with field grassland measures. The results showed that green vegetation had higher correlations with the grass coverage than dune and saline alkali soil. In addition, green vegetation also had higher correlation (R 2=0.62) than the ratio vegetation index (RVI), the normalized difference vegetation index (NDVI), the soil-Adjusted vegetation index (SAVI) and the modified soil-adjusted vegetation index (MSAVI). The results imply that it is feasible for assessing desert grassland coverage in the Northern Tianshan Mountains by using mixture pixel decomposition based on linear spectral mixture model. Source


Xu F.-X.,Fudan University | Dang Q.-K.,Fudan University | Chen Y.-J.,Fudan University | Yang K.,National Environment Monitoring Center | And 4 more authors.
Fenxi Huaxue/ Chinese Journal of Analytical Chemistry | Year: 2015

A fast mass analysis method using digital ion trap technology was reported. The mass analysis was realized by scanning the frequency of digital RF voltage and dipole ion resonance voltage during ion injection period without the conventional ion cooling, ion resonance ejection or ion cleaning process. It can decrease about three fourth of traditional analysis time using ion trap mass spectrometry. The ion signal was optimized through the modification of frequency scanning rate, ion gate voltage and other experimental parameters. For example, an optimal mass spectroscopy of reserpine (m/z 609) and arginine (m/z 174) were obtained when the ion gate voltage was 9 V and the digital RF frequency was scanned from 1 MHz to 400 kHz at rate of 2385 Th s-1. The results indicated that the obtained mass spectra were in very good agreement with conventional analytical method using ion trap mass analyzer. Copyright © 2015, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. Published by Elsevier Limited. All rights reserved. Source


Chen Y.,Fudan University | Xu C.,Fudan University | Xu F.,Fudan University | Yang K.,National Environment Monitoring Center | And 5 more authors.
Analytical Letters | Year: 2016

ABSTRACT: An electro-filtering spray ionization source for ambient mass spectrometry is reported. The ion source was assembled with a conical metal filter with a paper cone. The performance of the new ion source was characterized by the analysis of soil. Soil was directly introduced into the filter-paper cone and solvent was added. Ions were produced at the filter-paper tip when a high voltage was applied. The results by electro-filtering spray ionization were in good agreement with the results using conventional electrospray ionization with complex sample preparation. Advantages of electro-filtering spray ionization include simplicity, speed, and convenient operation that may allow in situ analysis in ambient atmospheric conditions. © 2016, Copyright © Taylor & Francis Group, LLC. Source

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