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| Shao, L.; Wang, Wanping; Griffiths, P.R.; Leytem, A.B.. |
| The choice of the type of background spectrum affects the credibility of open-path Fourier transform infrared (OP/FT-IR) spectroscopic data, and consequently the quality of data analysis. We systematically investigated several properties of the background spectrum. The results show that a short-path background measured with the lowest amplifier gain could significantly reduce noise in the calculated absorbance spectrum, by at least 30% in our case. We demonstrated that by using a short-path background, data analysis is more resistant to interferences, such as wavenumber shift or resolution alteration that occurs as a consequence of hardware aging or misalignment. We also discussed a systematic error introduced into quantitative analyses by the... |
| Tipo: Article |
Palavras-chave: Air Emissions. |
| Ano: 2013 |
URL: http://eprints.nwisrl.ars.usda.gov/1507/1/1470.pdf |
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| Shao, L.; Pollard, M.J.; Griffiths, P.R.; Westermann, D.T.; Bjorneberg, D.L.. |
| Over 32,000 interferograms measured during open-path Fourier transform infrared (OP/FT-IR) measurements at dairy and hog farms were evaluated for anomalies. Five types of anomalies could be distinguished: a reduction in the interferogram intensity because of weather-related optical misalignment; an increase in the amplitude of interferograms measured with too short a path-length that leads to a non-linear detector response; a periodic interference caused by wind-induced vibrations; the presence of spikes in the interferogram; and an increase in the noise level of the interferogram (and hence of the spectrum) because of the effect of electrical interference. Prior to testing for the presence of anomalous data, each interferogram is subjected to a... |
| Tipo: Article |
Palavras-chave: Research methodology; Mass Import - autoclassified (may be erroneous). |
| Ano: 2007 |
URL: http://eprints.nwisrl.ars.usda.gov/55/1/1217.pdf |
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| Shao, L.; Griffiths, P.R.; Leytem, A.B.. |
| The automated quantification of three greenhouse gases, ammonia, methane and nitrous oxide, in the vicinity of a large dairy farm by open-path Fourier transform infrared (OP/FT-IR) spectrometry at intervals of 5 minutes is demonstrated. Spectral pretreatment, including the detection and correction of the effect of interrupting the infrared beam is by a moving object, and ways of correcting for the effect, and correction for the nonlinear detector response are applied to the measured interferograms. Two ways of obtaining quantitative data from OP/FT-IR data are described. The first, which is installed in commercial OP/FT-IR spectrometers, is based on classical least squares (CLS) regression and the second is based on partial least squares (PLS)... |
| Tipo: Article |
Palavras-chave: Air Emissions. |
| Ano: 2010 |
URL: http://eprints.nwisrl.ars.usda.gov/1422/1/1392.pdf |
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