| 1. |
- Butt, Naveed, et al.
(författare)
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Robust Multichannel Detection of Mixtures Using Nuclear Quadrupole Resonance'
- 2008
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 56:10, s. 5042-5050
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Tidskriftsartikel (refereegranskat)abstract
- Nuclear quadrupole resonance (NQR) is a radio-frequency (RF) spectroscopic technique, able to detect the presence of many high explosives and narcotics. In practice, the weak NQR signal is often corrupted by strong RF interference (RFI); therefore, various multichannel detection algorithms have recently been proposed for NQR. However, these algorithms allow for only a single compound/polymorph, whose associated amplitudes are assumed to be known to within a scaling. Regrettably, these amplitudes are typically prone to some level of uncertainty; and, in several cases of interest, signals from a mixture of NQR compounds/polymorphs may be present, leading to performance degradation in the aforementioned algorithms. In this paper, we develop a robust multisensor hybrid algorithm able to process NQR signals from mixtures while also allowing for errors in the assumed amplitudes. Numerical investigations indicate that the proposed algorithm provides significant performance gains as compared to existing algorithms in the case when there are multiple polymorphs present and/or when uncertainties in the amplitudes exist.
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| 2. |
- Somasundaram, Samuel D., et al.
(författare)
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Enhancing Signals
- 2008
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Patent (populärvet., debatt m.m.)abstract
- A method of testing a sample comprising the steps of: applying an excitation to the sample; detecting a response signal from the sample; processing a first part and a second part of the response signal; and determining from the second part of the response signal information with which to enhance the first part of the response signal.
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| 3. |
- Somasundaram, Samuel D., et al.
(författare)
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Enhancing Signals
- 2008
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Patent (populärvet., debatt m.m.)
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| 4. |
- Somasundaram, Samuel D., et al.
(författare)
-
Robust Detection of Stochastic Nuclear Quadrupole Resonance Signals
- 2008
-
Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 56:9, s. 4221-4229
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Tidskriftsartikel (refereegranskat)abstract
- Nuclear quadrupole resonance (NQR) is a solid-state radio frequency (RF) spectroscopic technique, allowing the detection of compounds containing quadrupolar nuclei, a requirement fulfilled by many high explosives and narcotics. The practical use of NQR is restricted by the inherently low signal-to-noise ratio (SNR) of the observed signals, a problem that is further exacerbated by the presence of strong RF interference (RFI). The current literature focuses on the use of conventional, multiple-pulsed NQR (cNQR) to obtain signals. Here, we investigate an alternative method called stochastic NQR (sNQR), having many advantages over cNQR, one of which is the availability of signal-of-interest free samples. In this paper, we exploit these samples forming a matched subspace-type detector and a detector employing a prewhitening approach,, both of which are able to efficiently reduce the influence of RFI. Further, man), of the ideas already developed for cNQR, including providing robustness to uncertainties in the assumed complex amplitudes and exploiting the temperature dependencies of the NQR spectral components, are recast for sNQR. The presented detectors are evaluated on both simulated and measured trinitrotoluene (TNT) data.
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| 5. |
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