Dielectric Properties of Wheat at Microwave Frequencies

Chugh, Rajiv; Stuchly, S.S.; Rzepecka, Maria A.

doi:10.13031/2013.37656

Cited by 13 publications

(4 citation statements)

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“…It has been reported that water molecules show a characteristic Debye relaxation with a resonance frequency of 16.2 GHz at 20 °C, indicating that they have an extremely large D k (≈60) and D f (≈0.5) at approximately 10 GHz . This is because the hydrogen bonding network of water molecules induces intermolecular cooperative vibrations in the high-frequency range. − Thus, the effect of intermolecular interactions between PIs and adsorbed water on the dielectric properties should be considered, as suggested in our previous study . Recently, Zhang et al reported that both water absorption ( W A ) and D f have linear relationships with RH for 7 types of PIs and that the difference in W A is the main cause for the difference in D f , which complements the linear relationship between D k and RH shown by Mercer et al For further development of low-dielectric PIs, the influence of environmental humidity and hygroscopicity of polymers on their dielectric properties must be investigated based on the dielectric polarization effects described above.…”

Section: Introductionsupporting

confidence: 62%

Polarization Analysis and Humidity Dependence of Dielectric Properties of Aromatic and Semialicyclic Polyimides Measured at 10 GHz

Sawada,

Ando

2024

J. Phys. Chem. C

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In this study, dielectric constants (D k) and dissipation factors (D f) of 15 types of polyimides (PIs), including wholly aromatic, semialicyclic, partially fluorinated, and perfluorinated PIs, were measured in the transverse electric (TE011) mode at a frequency of 10 GHz and analyzed based on their chemical structures and the dominant factors of dielectric polarization per unit volume (P t). The relationships among the dipolar orientational (P d) and electronic (P e) polarizations and dielectric properties (D k and D f) were quantitatively investigated. Although a systematic correlation between the structure and D f of PIs has not yet been established, we found that the D f of PIs is anisotropic and linearly proportional to P d in the in-plane direction, which can be estimated from the D k and in-plane refractive index (n TE) at 1310 nm. This could be related to the bidirectional relationship between the real (D k) and imaginary (D f) parts of the relative permittivity. Furthermore, the D k and D f of all PIs increased linearly with respect to the relative humidity (RH) of the measurement environment, and their slopes (h Dk and h Df), i.e., the RH sensitivities of D k and D f, showed a proportional relationship with a high correlation coefficient (R 2 = 0.986). The weight fraction of polar imide and ester groups (Polar %) and the hydrophobicity of PIs, which are closely related to the fluorine content (F %), are essential factors in determining the values of D k, D f, h Dk, and h Df. These relationships are crucial for developing low-dielectric PI materials exhibiting low D k and D f values, as well as reduced sensitivity to humidity.

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Section: Introductionsupporting

confidence: 62%

Polarization Analysis and Humidity Dependence of Dielectric Properties of Aromatic and Semialicyclic Polyimides Measured at 10 GHz

Sawada,

Ando

2024

J. Phys. Chem. C

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“…The minimum number of nodes required to achieve the best RTI in the same area as reported in previous studies [ 5 , 6 , 7 ] is given in Equation (1).

where,…”

Section: Methodsmentioning

confidence: 99%

“…Moisture content can be defined as the weight of water in the grain mass and expressed in terms of percentage. Based on previous studies [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ], rice grain moisture content changes with changes in ambient humidity and local weather. Poor aeration could lead to moisture build-up within the bulk of the grain and reduce the quality of the grains.…”

Section: Introductionmentioning

confidence: 99%

“…To ensure that the quality of the grain is maintained, thereby reducing losses, it is essential to know the distribution of moisture content in the bulk of the stored grain continually and in real-time, if possible. Different methods had been developed for determining the moisture content of grains [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. However, to the best of the authors’ knowledge, none of the techniques proposes a real-time 3D moisture content measurement of stored rice.…”

Section: Introductionmentioning

confidence: 99%

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Inline 3D Volumetric Measurement of Moisture Content in Rice Using Regression-Based ML of RF Tomographic Imaging

Almaleeh

Zakaria

Kamarudin

et al. 2022

Sensors

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The moisture content of stored rice is dependent on the surrounding and environmental factors which in turn affect the quality and economic value of the grains. Therefore, the moisture content of grains needs to be measured frequently to ensure that optimum conditions that preserve their quality are maintained. The current state of the art for moisture measurement of rice in a silo is based on grab sampling or relies on single rod sensors placed randomly into the grain. The sensors that are currently used are very localized and are, therefore, unable to provide continuous measurement of the moisture distribution in the silo. To the authors’ knowledge, there is no commercially available 3D volumetric measurement system for rice moisture content in a silo. Hence, this paper presents results of work carried out using low-cost wireless devices that can be placed around the silo to measure changes in the moisture content of rice. This paper proposes a novel technique based on radio frequency tomographic imaging using low-cost wireless devices and regression-based machine learning to provide contactless non-destructive 3D volumetric moisture content distribution in stored rice grain. This proposed technique can detect multiple levels of localized moisture distributions in the silo with accuracies greater than or equal to 83.7%, depending on the size and shape of the sample under test. Unlike other approaches proposed in open literature or employed in the sector, the proposed system can be deployed to provide continuous monitoring of the moisture distribution in silos.

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Frequency and moisture dependence of the dielectric properties of hard red winter wheat

Nelson

Stetson

1976

Journal of Agricultural Engineering Research

112

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Dielectric Properties of Wheat at Microwave Frequencies

Cited by 13 publications

References 0 publications

Polarization Analysis and Humidity Dependence of Dielectric Properties of Aromatic and Semialicyclic Polyimides Measured at 10 GHz

Polarization Analysis and Humidity Dependence of Dielectric Properties of Aromatic and Semialicyclic Polyimides Measured at 10 GHz

Inline 3D Volumetric Measurement of Moisture Content in Rice Using Regression-Based ML of RF Tomographic Imaging

Frequency and moisture dependence of the dielectric properties of hard red winter wheat

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