26 April 2010 Method of THz spectrum dynamics analysis for identification of compound medium
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The method of THz spectrum dynamics analysis (SDA-method) is used for identification of compound media and detection of their components. The algorithm of identification is based on the SVD-method (method of Singular Value Decomposition) for reconstruction of the pulse shape by one set of measurements of integral characteristics from medium response during time intervals instead of the measurement of an instant medium response and on sliding window method for obtaining the spectrogram - dynamics of Fourier spectrum. It allows us to trace the dynamics of many spectral lines in one set of measurements and to obtain the full information about the spectrum dynamics of the signal, passed through the medium, even for measurements that are made over a short-term interval (less than 20 ps). We consider the examples imitating the mixture of explosive with harmless substances in different ratios. With this aim we analyze a sum of two signals, passed through both neutral material and explosive. Our investigations have shown that spectrogram of the signals sum differs clearness from spectrogram, obtained for neutral substance. Essential differences one can see in dynamics of spectral lines for both cases of signals. It is possible to detect the presence of additional substances in the mixture with neutral material even if the amplitude of the signal from explosive is 25 times less than the amplitude of the signal from neutral material. Therefore, the method allows for detecting and identifying the substance in compound media with high probability and can be very effective for defense and security applications. We compare as well the efficiency of our approach for identification of explosive with the efficiency of using the autocorrelation function and show that the autocorrelation function has less resolvability in comparison with the SDA-method.
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Vyacheslav A. Trofimov, Vyacheslav A. Trofimov, Svetlana A. Varentsova, Svetlana A. Varentsova, Jian Chen, Jian Chen, } "Method of THz spectrum dynamics analysis for identification of compound medium", Proc. SPIE 7671, Terahertz Physics, Devices, and Systems IV: Advanced Applications in Industry and Defense, 76710G (26 April 2010); doi: 10.1117/12.849983; https://doi.org/10.1117/12.849983

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