scholarly journals Terahertz Time Domain Spectroscopy of Transformer Insulation Paper after Thermal Aging Intervals

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2124 ◽  
Author(s):  
Liang Wang ◽  
Chao Tang ◽  
Shiping Zhu ◽  
Shengling Zhou
Keyword(s):  
Time Domain ◽  
Thermal Aging ◽  
Density Functional ◽  
Degree Of Polymerization ◽  
Transformer Oil ◽  
Optical Parameters ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Paper Insulation ◽  
Transformer Insulation

An accelerated thermal aging process was used to simulate the condition of paper insulation in transformer oil-paper systems. Optical parameters of the insulation paper after various aging intervals were analyzed with terahertz time-domain spectroscopy (THz-TDS) over the range 0.1~1.8 THz. The result shows that the paper had seven absorption peaks at 0.19, 0.49, 0.82, 1.19, 1.43, 1.53, and 1.74 THz, and density functional theory of B3LYP/6-311G+ (d, p) was used to simulate the molecular dynamics of the repeating component (cellobiose) of the cellulose paper. Theoretical spectra were consistent with experiment, which had absorption peaks at 0.18, 0.82, 1.47, and 1.53 THz in the same frequency range. At the same time, the paper samples after various aging intervals had different refractive indexes, and least squares fitting revealed a linear relationship between the degree of polymerization and the refractive index of the paper. Hence, this paper demonstrates that THz-TDS could be used to analyze the aging condition of transformer insulation paper and provides the theoretical and experimental basis for detection.

scholarly journals Terahertz time-domain spectroscopy of edible oils

2017 ◽  
Vol 4 (6) ◽  
pp. 170275 ◽  
Author(s):  
Alex Dinovitser ◽  
Dimitar G. Valchev ◽  
Derek Abbott
Keyword(s):  
Time Domain ◽  
Edible Oils ◽  
Morphological Changes ◽  
Smoke Point ◽  
Chemical Degradation ◽  
Optical Parameters ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Null Result ◽  
Physical Changes

Chemical degradation of edible oils has been studied using conventional spectroscopic methods spanning the spectrum from ultraviolet to mid-IR. However, the possibility of morphological changes of oil molecules that can be detected at terahertz frequencies is beginning to receive some attention. Furthermore, the rapidly decreasing cost of this technology and its capability for convenient, in situ measurement of material properties, raises the possibility of monitoring oil during cooking and processing at production facilities, and more generally within the food industry. In this paper, we test the hypothesis that oil undergoes chemical and physical changes when heated above the smoke point, which can be detected in the 0.05–2 THz spectral range, measured using the conventional terahertz time-domain spectroscopy technique. The measurements demonstrate a null result in that there is no significant change in the spectra of terahertz optical parameters after heating above the smoke point for 5 min.

scholarly journals Study of 2,4-D Spectral Characteristics and Its Detection in Zizania Latifolia Using Terahertz Time-Domain Spectroscopy

2019 ◽  
Vol 9 (11) ◽  
pp. 2248
Author(s):  
Pengcheng Nie ◽  
Chengyong Cai ◽  
Fangfang Qu ◽  
Lei Lin ◽  
Tao Dong ◽  
...  
Keyword(s):  
Time Domain ◽  
Density Functional ◽  
Terahertz Spectroscopy ◽  
Spectral Characteristics ◽  
Geometry Optimization ◽  
Main Peak ◽  
Terahertz Time Domain Spectroscopy ◽  
Zizania Latifolia ◽  
Time Domain Spectroscopy ◽  
2,4 Dichlorophenoxyacetic Acid

2,4-Dichlorophenoxyacetic acid (2,4-D) is a common plant growth regulator, which can remain in food and, with long-term consumption, threaten human health. Therefore, it is necessary to propose an effective detection method. Terahertz time-domain spectroscopy technique (THz-TDS) has good advantages in the quantitative and qualitative analysis of most biomolecules due to its rich fingerprint characteristics. In this paper, density functional theory (DFT) was applied to geometry optimization and frequency vibration calculation of 2,4-D, and THz-TDS was used to quantitatively detect 2,4-D in Zizania latifolia. The results showed that there were three characteristic absorption peaks of 2,4-D at 1.36, 1.60, and 2.38 THz, respectively, and the theoretical spectra were in good consistency with experimental spectra, with slight discrepancies. Additionally, the absorption peak at 1.36 THz had the best absorption characteristics and was chosen as the main peak for 2,4-D quantitative analysis. It was demonstrated that the limits of detection (LOD) of 2,4-D in Zizania latifolia were found to be as low as 5%, the absorbance intensity at 1.36 THz showed a good linear relationship (R2 = 0.9854) with 2,4-D concentration from 5% to 30%, and the recovery was 93.29%–98.75%. Overall, this work enriched the fingerprint database of pesticide molecules on the basis of terahertz spectroscopy and could provide a technical support for the detection of 2,4-D in food by terahertz spectroscopy.

Accurate and rapid extraction of optical parameters for thin plates with terahertz time-domain spectroscopy technology

2017 ◽  
Vol 46 (5) ◽  
pp. 525003 ◽  
Author(s):  
韩晓惠 Han Xiaohui ◽  
崔洪亮 Cui Hongliang ◽  
张 瑾 Zhang Jin ◽  
杨 晔 Yang Ye ◽  
马宇婷 Ma Yuting ◽  
...  
Keyword(s):  
Time Domain ◽  
Thin Plates ◽  
Optical Parameters ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Rapid Extraction

Dielectric Properties of Carbon-Materials-Filled Composites Characterized by Terahertz Time-Domain Spectroscopy

2011 ◽  
Vol 295-297 ◽  
pp. 1408-1413 ◽  
Author(s):  
Xi Liang Chen ◽  
Xin Chen ◽  
Dang Sheng Li ◽  
Zhi Yong Zhu
Keyword(s):  
Refractive Index ◽  
Time Domain ◽  
Carbon Materials ◽  
Volume Fraction ◽  
Filler Concentration ◽  
Optical Parameters ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Carbon Particles ◽  
The Matrix

The optical properties of composites, formed by filling the high density polyethylene (HDPE) with carbon black (CB), multi-walled carbon nanotubes (MWNTs) and fullerene (C60), respectively, in the frequence region from 0.3 to 2.0 terahertz (THz) were characterized with THz time-domain spectroscopy (THz-TDS). It is found that the optical parameters and the details of their variation with frequence and filler concentration are significantly different for different kinds of carbon materials. The MWNTs filled composites have the biggest absorption coefficient value, refractive index and real conductivity. The C60/HDPE composite shows very little changes in absorption and refractive index compared to that of the HDPE even at a filler-content of 12.3% in volume fraction. These phenomena are related to the special properties of the fillers as well as their particulate structures, such as aspect ratio, particle size, and aggregate structure, etc. The results are analyzed by using Cole-Cole theory of dipole relaxation under the assumption that carbon particles dispersed in the matrix behave like dipoles.

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