scholarly journals A Possible Way for the Detection and Identification of Dangerous Substances in Ternary Mixtures Using THz Pulsed Spectroscopy

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2365 ◽  
Author(s):  
Vyacheslav A. Trofimov ◽  
Svetlana A. Varentsova
Keyword(s):  
Spectral Properties ◽  
Main Pulse ◽  
Ternary Mixtures ◽  
Thz Spectroscopy ◽  
Time Intervals ◽  
Detection And Identification ◽  
Dangerous Substances ◽  
Spectral Intensities ◽  
Absorption Frequencies ◽  
High Absorption

We discuss an effective tool for the detection and identification of substances in ternary mixtures with similar spectral properties using a broadband reflected THz signal. Nowadays, this is an urgent problem; its effective solution is still far off. Two ternary mixtures of the explosives (RDX+TNT+HMX and RDX+TNT+PETN) were used as the examples for demonstration of the efficiency of the method proposed. The identification is based on the pulsed THz spectroscopy. We follow the spectral intensities together with the use of integral correlation criteria. They use the spectral line dynamics of the THz pulse reflected from the substance under investigation and that of the standard THz signal from database. In order to increase the accuracy and reliability of the identification, we analyze the partial non-overlapping time intervals, containing the main pulse of the reflected THz signal and the sequential sub-pulses. The main pulse is shown to contain information about high absorption frequencies (ν > 2.6 THz) of the mixture components. In the sub-pulses, the absorption frequencies of the components are detected in the range of low (ν < 2.6 THz) and high (ν > 2.6 THz) frequencies. The opportunity of distinguishing the mixtures with similar spectral properties is also shown.

scholarly journals Spurious Absorption Frequency Appearance Due to Frequency Conversion Processes in Pulsed THz TDS Problems

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1859
Author(s):  
Vyacheslav A. Trofimov ◽  
Nan-Nan Wang ◽  
Jing-Hui Qiu ◽  
Svetlana A. Varentsova
Keyword(s):  
Nonlinear Response ◽  
Frequency Conversion ◽  
Pulse Propagation ◽  
Frequency Doubling ◽  
Absorption Frequency ◽  
Physical Experiments ◽  
Detection And Identification ◽  
Dangerous Substances ◽  
Spectral Intensities ◽  
Absorption Frequencies

The appearance of the spurious absorption frequencies caused by the frequency conversion process at the broadband THz pulse propagation in a medium is theoretically and experimentally discussed. The spurious absorption frequencies appear due to both the frequency doubling and generation of waves with sum or difference frequency. Such generation might occur because of the nonlinear response of a medium or its non-instantaneous response. This phenomenon is confirmed by the results of a few physical experiments provided with the THz CW signals and broadband THz pulses that are transmitted through the ordinary or dangerous substances. A high correlation between the time-dependent spectral intensities for the basic frequency and generated frequencies is demonstrated while using the computer simulation results. This feature of the frequency conversion might be used for the detection and identification of a substance.

VUV Spectral Properties of MBPO7 Co-Doped with Tm3+ ,Gd3+

2008 ◽  
Vol 368-372 ◽  
pp. 366-368 ◽  
Author(s):  
Xin Li ◽  
Da Wei He ◽  
Peng Zhi Lu ◽  
Yong Sheng Wang
Keyword(s):  
Spectral Properties ◽  
Vacuum Ultraviolet ◽  
Emission Spectra ◽  
Lattice Parameters ◽  
Excitation Spectra ◽  
Strong Emission ◽  
Emission Transition ◽  
Crystal Lattice Parameters ◽  
Co Doped ◽  
High Absorption

A series of phosphor of MBPO7:Tm3+, and MBPO7:Tm3+, Gd3+ (M= Mg, Sr, Ca) were prepared and studied. The XRD data showed Tm3+, Gd3+ didn’t affects the lattice parameters. Excitation spectra exhibited high absorption in vacuum ultraviolet (VUV) region. There existed strong emission peaking at 453nm and 363nm correspond to the 1D2 →3HJ (J=4, 6) emission transition of Tm 3+ when excited under VUV. With the changes of cation in the samples, the excitation spectra changed greatly, and lead a great change in its emission spectra. The crystal lattice parameters affect the ratio of intensity of the peak at 454nm and 312nm.

Accurate THz Ellipsometry Using Calibration in Time Domain

2021 ◽  
Author(s):  
Zahra Mazaheri ◽  
Can Koral ◽  
Antonello Andreone
Keyword(s):  
Time Domain ◽  
Parameter Extraction ◽  
Calibration Procedure ◽  
Thz Spectroscopy ◽  
Angle Of Incidence ◽  
Liquid Form ◽  
Calibration Methods ◽  
Wide Range ◽  
Transmission Measurements ◽  
High Absorption

Abstract We report on the realisation of a customized THz Time Domain Spectroscopic Ellipsometer (THz-TDSE) based on fiber-coupled photoconductive antennas, operating in a wide range of incident angles and allowing also standard transmission spectroscopy without any optical realignment. To ensure accurate parameter extraction for a broad range of materials, we developed a fast and effective algorithm-assisted method to calibrate the setup and compensate for the nonideality in the response of the THz system. The procedure allows to minimise errors induced by imperfect response of the antennas and polarizers, imprecise setting of the impinging and receiving angles in the goniometric mechanical arms, and unavoidable mismatches in the THz beam optics. Differently from other calibration methods applied in the literature, our approach compares in time domain the ellipsometric derived electric field s- and p-polarised components at a given angle of incidence with the reconstructed ones, attained by using the complex dielectric function of a known sample. The calibrated response is determined with high precision by setting the system in transmission mode. In order to validate the technique, ellipsometric measurements have been carried out at various angle of incidences on a number of materials both in solid and liquid form, and their data compared with what obtained by conventional THz spectroscopy. Results show that THz-TDSE accompanied with an accurate calibration procedure is an effective technique for material characterization, especially in case of samples with a high absorption rate that are not easily investigated through transmission measurements.

scholarly journals On the Intrinsic Simplicity of Spectral Variability of GRBs

10.14311/1322 ◽  
2011 ◽  
Vol 51 (1) ◽  
Author(s):  
A. Chernenko
Keyword(s):  
Correlation Analysis ◽  
Physical Parameter ◽  
Spectral Properties ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
Spectral Variability ◽  
Time Intervals ◽  
Multi Scale

In this paper we present a Multi-Scale Correlation Analysis (MSCA) of the light curves of gamma-ray bursts recorded in different energy ranges. This analysis allows us to identify time intervals where emission variability can be reduced to a single physical parameter and can therefore be robustly attributed to a single physical emitter. The properties of these intervals can then be investigated separately, and the spectral properties of individual emitters can be analysed. The signatures of hidden dynamical relations between individual emitters are also discussed.

Rotational Characteristics of the Green Solar Corona: 1947-1991

1994 ◽  
Vol 144 ◽  
pp. 139-141 ◽  
Author(s):  
J. Rybák ◽  
V. Rušin ◽  
M. Rybanský
Keyword(s):  
Solar Corona ◽  
World Wide ◽  
Rotation Period ◽  
Original Data ◽  
Coronal Emission ◽  
Time Intervals ◽  
Data Set ◽  
The World ◽  
Coronal Emission Line ◽  
Homogeneous Data

AbstractFe XIV 530.3 nm coronal emission line observations have been used for the estimation of the green solar corona rotation. A homogeneous data set, created from measurements of the world-wide coronagraphic network, has been examined with a help of correlation analysis to reveal the averaged synodic rotation period as a function of latitude and time over the epoch from 1947 to 1991.The values of the synodic rotation period obtained for this epoch for the whole range of latitudes and a latitude band ±30° are 27.52±0.12 days and 26.95±0.21 days, resp. A differential rotation of green solar corona, with local period maxima around ±60° and minimum of the rotation period at the equator, was confirmed. No clear cyclic variation of the rotation has been found for examinated epoch but some monotonic trends for some time intervals are presented.A detailed investigation of the original data and their correlation functions has shown that an existence of sufficiently reliable tracers is not evident for the whole set of examinated data. This should be taken into account in future more precise estimations of the green corona rotation period.

The Interpretation of Solar Spectral Intensities

1988 ◽  
Vol 102 ◽  
pp. 329
Author(s):  
R.W.P. McWhirter
Keyword(s):  
Emission Measure ◽  
Physical Nature ◽  
Atomic Data ◽  
The Sun ◽  
Atomic Properties ◽  
Outer Atmosphere ◽  
Spectral Intensities ◽  
Thin Plasma ◽  
Number Of Authors

The intensity of a specrtal line from an optically thin plasma such as the outer atmosphere of the sun depends on both the atomic properties of the atomic ion responsible for the line and the physical nature of the plasma. In this paper we discuss the various ways in which the measured spectral intensities from the sun are used to discover something about the nature of the sun’s atmosphere. The technique has been referred to as the emission measure method. It has important limitations in terms of the accuracy of the specrtal data as well as the atomic data. We discuss some of these and suggest methods by which they may be assessed. The technique is illustrated by application to real observations from a number of authors.

Prolonged Fixation Studies For Spaceflight

1973 ◽  
Vol 31 ◽  
pp. 332-333
Author(s):  
Robert Corbett ◽  
Delbert E. Philpott ◽  
Sam Black
Keyword(s):  
High Pressure ◽  
Living Systems ◽  
Prolonged Storage ◽  
Time Intervals ◽  
Early Signs ◽  
Large Numbers

Observation of subtle or early signs of change in spaceflight induced alterations on living systems require precise methods of sampling. In-flight analysis would be preferable but constraints of time, equipment, personnel and cost dictate the necessity for prolonged storage before retrieval. Because of this, various tissues have been stored in fixatives and combinations of fixatives and observed at various time intervals. High pressure and the effect of buffer alone have also been tried.Of the various tissues embedded, muscle, cartilage and liver, liver has been the most extensively studied because it contains large numbers of organelles common to all tissues (Fig. 1).

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