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Extension of the p-Spectrum Method to the Higher Frequencies

100%
Pałka N.
Acta Physica Polonica A
|
2013
|
vol. 124
|
issue 3
534-537
EN
The p-spectrum method is a time domain spectroscopy-based technique for reflection analysis of materials (including explosives) that takes into account only part of the reflected signal, which is next analyzed via the Fourier transform. The method is limited to the frequencies of about 1.8 THz due to the pulse properties of our time domain spectroscopy setup. In this paper we theoretically prove that application of a shorter pulse can increase this frequency range up to 2.2 THz, that enables analysis of penthrite and octogen, two important explosives.
2
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Terahertz Frequency Domain Spectroscopy Identification System Based on Decision Trees

51%
Ryniec R., Zagrajek P., Pałka N.
Acta Physica Polonica A
|
2012
|
vol. 122
|
issue 5
891-895
EN
The application of pattern recognition methodology within chemistry, biology and other science domains, especially in security systems is becoming more and more important. Many classification algorithms are available in literature but decision trees are the most commonly exploited because of their ease of implementation and understanding in comparison to other classification algorithms. Decision trees are powerful and popular tools for classification and prediction. In contrast to neural networks, decision trees represent rules, which can readily be expressed so that humans can understand them or even directly use in a database. In this paper we present an algorithm of construction of decision trees and a classification rule extraction based on a logical relationship between attributes and a generalized decision function. Moreover, correctness and efficiency of the algorithm was experimentally validated in a terahertz system, where spectra of explosives were measured in reflection configuration.
3
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Transmission Spectra of Materials in the Terahertz Range Measured by a Hot Electron Bolometer-Based System

39%
Pałka N., Walczakowski M., Zagrajek P., Czerwiński A., Sypek M., Szustakowski M.
Acta Physica Polonica A
|
2013
|
vol. 124
|
issue 3
538-541
EN
This paper presents an optical system for transmission spectral measurements in the terahertz range. The source of radiation is a tunable solid-state laser, which generates a narrow-band nanosecond pulses in the range 0.67-2.68 THz and based on optical parametric oscillator phenomenon. The signal is detected with a fast and sensitive hot electron bolometer. Principle of generation and detection of pulses as well as methodology of measuring spectral characteristics are presented. We compared the results obtained with the free-space setup, which is based on the optical parametric oscillator and hot electron bolometer, with a purged time domain spectroscopy system in the range of 0.7-2.2 THz.
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