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Journal articles on the topic 'Permittivity'

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1

Raszewski, Zbigniew, Stanisław Kłosowicz, Jerzy Zieliński, and Rafał Mazur. "Dielectric properties of liquid crystals." Bulletin of the Military University of Technology 72, no. 4 (2023): 15–54. http://dx.doi.org/10.5604/01.3001.0054.7909.

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In the paper, dielectric properties of liquid crystals, especially the nematic phase, arediscussed. An outline of the development of theories describing these properties is presented. Thestatic theory of dielectric permittivity of anisotropic nematic liquid crystals on Onsager, Maier andMeier approach is discussed in details. In this view, anisotropic properties of dielectric permittivityof nematics as well parameters describing these properties are presented.Keywords: material science, liquid crystals, nematics, dielectric permittivity, electron polarisability,constant and induced dipole moment of molecule, vectors of electric field intensity, induction andpolarisation in nematic phase.
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2

Blahovec, J., and J. Sobotka. "Potato tuber permittivity during deformation in compression." Research in Agricultural Engineering 53, No. 3 (2008): 79–84. http://dx.doi.org/10.17221/2124-rae.

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Potato tuber specimens of two varieties (Nicola and Saturna) were deformed in a compression loading/unloading test. The tuber complex permittivity spectrum at frequencies 0.1–500 kHz was measured repeatedly during the deformation. The results show that both parts of relative permittivity (real and imaginary) decrease with increasing deformation and vice versa. The same trend was observed at all studied frequencies even if it was not equally strong in all cases. The permittivity plots versus frequency were similar in both the tested varieties and in different stages of deformation. The influence of tuber deformation on the permittivity values as well as the reversibility of the permittivity changes during the deformation are changed substantially at strains about 20% in comparison to strains up to 10%. The obtained results support the hypothesis that permittivity measurements can serve as an alternative indication of the internal structural changes in potato tissue during its loading.
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3

Leśnikowski, Jacek. "Prediction of Electric Permittivity of Threads in Woven Fabric." Autex Research Journal 18, no. 1 (2018): 80–85. http://dx.doi.org/10.1515/aut-2017-0031.

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Abstract In the article, a new method for the estimation of electric permittivity of threads (filaments) was presented. The proposed recursive method is based on the results of computer simulation of 3D model of transmission stripline. This model contains a model of flat fabric having threads, with which electric permittivity should be determined. The described procedure uses the method proposed by Barry to obtain permittivity of flat fabric from the so-called s parameters of the simulated stripline. In the proposed method, the permittivity of the flat fabric obtained from simulation is compared with the measured value of permittivity of real flat fabric in order to estimate the threads’ permittivity. This comparison is needed to obtain the electric permittivity of threads forming this fabric. The article also presents examples of the obtained values of threads’ permittivity and discussion about the accuracy of the method. The presented method will be useful in situations where the knowledge of permittivity of threads is necessary in the conducted research.
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4

Fam, M. A., and M. B. Dusseault. "High-frequency complex permittivity of shales (0.02-1.30 GHz)." Canadian Geotechnical Journal 35, no. 3 (1998): 524–31. http://dx.doi.org/10.1139/t98-014.

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This study describes a new approach to analyze complex permittivity data of shales and to extract fundamental properties relevant to engineering applications. The complex permittivity at high frequencies was measured for three different shales: Queenston, Mancos, and Pierre shales. Plane surfaces parallel and perpendicular to the bedding plane were cut from well-preserved cores. Permittivity data were acquired using a coaxial termination probe and a network analyzer (0.02-1.30 GHz). It is shown that Pierre shale displays high complex permittivity values relative to Queenston and Mancos shales. A simple approach is adopted to extract the volumetric free-water content of shales based on permittivity data at high frequencies. Shales with high specific surface (e.g., Pierre shale) show the lowest free-water content among tested cores. The slope of the relationship between real permittivity and frequency in a semi-log plot is suggested to relate permittivity data to the specific surface. The anisotropy in complex permittivity is a potential parameter in shale characterization. The permittivity anisotropy depends on the reactivity and the clay content of the shale, as well as on the inherent fabric anisotropy.Keywords: permittivity, clay content, specific surface, free-water content, anisotropy
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5

Kuz’min, V. L., V. P. Romanov, and E. P. Obraztsov. "Permittivity of suspensions." Optics and Spectroscopy 93, no. 6 (2002): 923–29. http://dx.doi.org/10.1134/1.1531718.

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6

Varyukhin, S. V., and A. A. Zakharov. "La2CuO4 permittivity anisotropy." Soviet Journal of Low Temperature Physics 17, no. 10 (1991): 756–58. https://doi.org/10.1063/10.0033004.

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7

Ming Chen and Chi-Chih Chen. "Improved Permittivity Calibration Method for Wideband In Situ Permittivity Probe." IEEE Geoscience and Remote Sensing Letters 10, no. 2 (2013): 323–27. http://dx.doi.org/10.1109/lgrs.2012.2205366.

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8

Li, Yuyan, Huan Ye, Yunpeng Qu, Zongxiang Wang, and Kai Sun. "Communication—Function-Oriented Design of 3D Carbon Networks Toward Negative Permittivity at kHz Frequencies." ECS Journal of Solid State Science and Technology 11, no. 1 (2022): 013011. http://dx.doi.org/10.1149/2162-8777/ac4bac.

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Three-dimensional (3D) carbon networks composed of graphene (GR) and carbon nanotube (CNT) were constructed in copper calcium titanate (CCTO) in order to realize negative permittivity behavior. The results show that negative permittivity can be obtained at kHz frequencies above percolation threshold when 3D carbon networks are successfully constructed. Negative permittivity originates from the low-frequency plasmonic state which is explained by Drude model. The magnitude of negative permittivity was tuned between 105 and 106 which significantly correlates with concentration of free carriers. Moreover, the reactance spectra clarify the inductive character of negative permittivity materials.
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9

Gou, Mingyi, Qian Chen, Penghao Dong, Changjun Liu, and Kama Huang. "Design of a Microwave Heating and Permittivity Measurement System Based on Oblique Aperture Ridge Waveguide." Sensors 23, no. 8 (2023): 4035. http://dx.doi.org/10.3390/s23084035.

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In this paper, an oblique aperture ridge waveguide operating at 2450 MHz is proposed, and, using the ridge waveguide, a permittivity measurement system is constructed which can measure the permittivity of materials during microwave heating. The system calculates the amplitudes of the scattering parameters by using the forward, reflected and transmitted powers of the power meters, and it reconstructs the permittivity of the material by combining the scattering parameters with an artificial neural network. The system is used to measure the complex permittivity of mixed solutions of methanol and ethanol with different ratios at room temperature, and the permittivity of methanol and ethanol with increasing temperature, from room temperature to 50 °C. The measured results are in good agreement with the reference data. The system allows simultaneous measurement of the permittivity with microwave heating and provides real-time, rapid changes in the permittivity during heating, avoiding thermal runaway and providing a reference for applications of microwave energy in the chemical industry.
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10

Sun, Kai, Ao Ma, Pengtao Yang, et al. "Flexible Copper Nanowire/Polyvinylidene Fluoride Membranous Composites with a Frequency-Independent Negative Permittivity." Polymers 15, no. 23 (2023): 4486. http://dx.doi.org/10.3390/polym15234486.

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With the increasing popularity of wearable devices, flexible electronics with a negative permittivity property have been widely applied to wearable devices, sensors, and energy storage. In particular, a low-frequency dispersion negative permittivity in a wide frequency range can effectively contribute to the stable working performance of devices. In this work, polyvinylidene fluoride (PVDF) was selected as the flexible matrix, and copper nanowires (CuNWs) were used as the conductive functional filler to prepare a flexible CuNWs/PVDF composite film with a low-frequency dispersion negative permittivity. As the content of CuNWs increased, the conductivity of the resulting composites increased sharply and presented a metal-like behavior. Moreover, the negative permittivity consistent with the Drude model was observed when CuNWs formed a percolative network. Meanwhile, the negative permittivity exhibited a low-frequency dispersion in the whole test frequency range, and the fluctuation of the permittivity spectra was relatively small (−760 to −584) at 20 kHz–1 MHz. The results revealed that the high electron mobility of CuNWs is reasonable for the low-frequency dispersion of negative permittivity. CuNWs/PVDF composite films with a frequency-independent negative permittivity provide a new idea for the development of flexible wearable electronic devices.
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11

Chen, Qian, Yang Yang, Ka Ma Huang, Cheng Chen, and Kai Yong Wang. "A Permittivity Measurement Method Based on Cavity Perturbation Technique." Applied Mechanics and Materials 590 (June 2014): 629–33. http://dx.doi.org/10.4028/www.scientific.net/amm.590.629.

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Effective complex permittivity measurements of materials are important in microwave engineering and microwave chemistry. This paper describes a convenient laboratory method designed to obtain the permittivity for some materials. The hole for temperature measurement has been designed. The permittivity of materials at deferent temperature can be measured. The measurement results of the real part and imaginary part of the permittivity agree well with literature data at 2.45GHz.
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12

Chen, Min, Kai Sun, Xuai Wang, and Yanmin Wang. "Communication—Tunable Negative Permittivity of Cobalt and Epoxy Composites at 3 kHz ∼ 1 MHz Frequency Regions." ECS Journal of Solid State Science and Technology 10, no. 12 (2021): 123007. http://dx.doi.org/10.1149/2162-8777/ac3e45.

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Negative permittivity in percolation composites has drawn much attention owing to their potential application. This study set out to explore whether tunable negative permittivity can be realized in metal composites at 3 kHz ∼ 1 MHz frequency regions. When the content of cobalt is 80 wt%, the permittivity turns to negative in the test band. These findings show that the Co conductive network has formed and provides large numbers of free electrons. Meanwhile, the percolation composites with negative permittivity show inductive characteristic. This research supports the idea that tunable low-frequency negative permittivity can be realized in metal composites.
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13

Liu, Yao, Ciqun Xu, Huan Ren, Zaixin Wei, and Zidong Zhang. "Tailorable negative permittivity in Fe/BaTiO3 meta-composites." Functional Materials Letters 13, no. 03 (2020): 2050017. http://dx.doi.org/10.1142/s1793604720500174.

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Meta-composites with negative permittivity are promising candidates for future electronics such as microwave absorbers, novel capacitors, etc. In this work, we proposed to develop the Fe/BaTiO3 meta-composites with tuneable negative permittivity. Fe content influenced the conductivity of composites and even led to the change of the conductive mechanism. The tuneable permittivity behavior was achieved by controlling the Fe fraction, and the plasma oscillation theory was employed to explain the negative permittivity behavior. Meanwhile, a frequency-switched negative permittivity was observed in this composite, which could be used to extend applications of meta-composites.
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14

Jones, Scott B., Wenyi Sheng, and Dani Or. "Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications." Sensors 22, no. 6 (2022): 2083. http://dx.doi.org/10.3390/s22062083.

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Moisture content is a critical variable for the harvesting, processing, storing and marketing of cereal grains, oilseeds and legumes. Efficient and accurate determination of grain moisture content even with advanced nondestructive techniques, remains a challenge due to complex water-retaining biological structures and hierarchical composition and geometry of grains that affect measurement interpretation and require specific grain-dependent calibration. We review (1) the primary factors affecting permittivity measurements used in practice for inferring moisture content in grains; (2) develop novel methods for estimating critical parameters for permittivity modeling including packing density, porosity, water binding surface area and water phase permittivity and (3) represent the permittivity of packs of grains using dielectric mixture theory as a function of moisture content applied to high moisture corn (as a model grain). Grain permittivity measurements are affected by their free and bound water contents, chemical composition, temperature, constituent shape, phase configuration and measurement frequency. A large fraction of grain water is bound exhibiting reduced permittivity compared to that of free water. The reduced mixture permittivity and attributed to hydrophilic surfaces in starches, proteins and other high surface area grain constituents. The hierarchal grain structure (i.e., kernel, starch grain, lamella, molecule) and the different constituents influence permittivity measurements due to their layering, geometry (i.e., kernel or starch grain), configuration and water-binding surface area. Dielectric mixture theory offers a physically-based approach for modeling permittivity of agricultural grains and similar granular media.
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15

Mavrovic, Alex, Renato Pardo Lara, Aaron Berg, François Demontoux, Alain Royer, and Alexandre Roy. "Soil dielectric characterization during freeze–thaw transitions using L-band coaxial and soil moisture probes." Hydrology and Earth System Sciences 25, no. 3 (2021): 1117–31. http://dx.doi.org/10.5194/hess-25-1117-2021.

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Abstract. Soil microwave permittivity is a crucial parameter in passive microwave retrieval algorithms but remains a challenging variable to measure. To validate and improve satellite microwave data products, precise and reliable estimations of the relative permittivity (εr=ε/ε0=ε′-jε′′; unitless) of soils are required, particularly for frozen soils. In this study, permittivity measurements were acquired using two different instruments: the newly designed open-ended coaxial probe (OECP) and the conventional Stevens HydraProbe. Both instruments were used to characterize the permittivity of soil samples undergoing several freeze–thaw cycles in a laboratory environment. The measurements were compared to soil permittivity models. The OECP measured frozen (εfrozen′=[3.5; 6.0], εfrozen′′=[0.46; 1.2]) and thawed (εthawed′=[6.5; 22.8], εthawed′′=[1.43; 5.7]) soil microwave permittivity. We also demonstrate that cheaper and widespread soil permittivity probes operating at lower frequencies (i.e., Stevens HydraProbe) can be used to estimate microwave permittivity given proper calibration relative to an L-band (1–2 GHz) probe. This study also highlighted the need to improve dielectric soil models, particularly during freeze–thaw transitions. There are still important discrepancies between in situ and modeled estimates and no current model accounts for the hysteresis effect shown between freezing and thawing processes, which could have a significant impact on freeze–thaw detection from satellites.
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16

Sharma, Arun, K. C. Pancholi, and S. P. Bhatnagar. "Complex Dielectric Permittivity of Sandy Loam as a Function of Salinity and Biomass at Microwaves." Solid State Phenomena 209 (November 2013): 116–20. http://dx.doi.org/10.4028/www.scientific.net/ssp.209.116.

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Real and Imaginary parts of Complex Dielectric Permittivity (ε’ and ε” ) of Sandy Loam soil have been measured in the frequency range 150 MHz – 2.4 GHz using a Vector Network Analyzer at varied Moisture contents, Salinity and Biomass. The Emissivity of the soil for normal incidence was also calculated from measured values of Complex Permittivity. The measured permittivity data show strong dependence on moisture content. Salinity causes higher permittivity and dielectric loss. Biomass appears to enhance the permittivity data due to increase in porosity of the soil. The emissivity of the soil was observed to decrease with increasing soil moisture and soil salinity, but it increases with biomass.
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17

Seleznev, Nikita V., Kamilla Fellah, John Phillips, Siti Najmi Zulkipli, and Bastien Fournié. "Matrix Permittivity Measurements for Rock Powders." SPE Reservoir Evaluation & Engineering 19, no. 02 (2016): 214–25. http://dx.doi.org/10.2118/170896-pa.

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Summary Formation water content is one of the key petrophysical quantities provided by dielectric logging. However, to determine water content from formation permittivity measurements, the rock matrix permittivity must be known. Uncertainty in the rock matrix permittivity values translates into uncertainty in the water-content estimate, which is especially important in low-porosity formations or complex lithologies. Matrix permittivity values are not well-known for a number of minerals and can also vary for the same type of mineral in different formations. Thus, a laboratory methodology for the accurate determination of matrix permittivity at dielectric logging frequencies is required to facilitate accurate log interpretation. One can measure matrix permittivity values on solid plugs (Seleznev et al. 2011). However, the plug-based methodology can be challenging in very-low-permeability or unconventional reservoirs because of difficulties with plug drying. In addition, it is not readily applicable to unconsolidated formations. Finally, it may be impossible to cut solid plugs because of limited availability of rock material. Matrix permittivity measurements made on rock powders are capable of addressing all these issues. We introduce a methodology for laboratory measurements of matrix permittivity on rock powders at 1 GHz. The methodology is based on conducting dielectric measurements on mixtures of rock powders and liquids with variable permittivities in a dielectric resonator. The permittivity of the rock matrix is inverted from a series of measurements obtained on pure liquids and powder/liquid mixtures. The methodology was benchmarked on a collection of samples representing common oilfield lithologies with matrix-permittivity values between 4.6 and 8.6. The reference matrix-permittivity values were first measured on solid plugs. Then, the plugs were crushed into powders, and the matrix permittivity values were determined on powders following the proposed methodology. The values obtained on powders matched the ones measured on solid plugs within 0.2 dielectric units, resulting in accuracies better than 1% for the water-filled porosity and better than 1,000 ppm for water salinity. This new methodology was applied to a number of core samples from a carbonate reservoir offshore Sarawak, where dielectric logging was performed along with conventional core analysis. The resulting measured matrix permittivity values were then used to interpret the dielectric log measurement. Results showed a better estimation of water-filled porosity and of the textural MN parameter, equivalent to the Archie's cementation exponent in a water-bearing zone, than would have resulted from using “chartbook” values of matrix permittivity. A consistent and optimized interpretation was obtained in porosities ranging from 5% to more than 30%.
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18

Qu, Yunpeng, Guohua Fan, and Yao Liu. "Tunable negative permittivity in Ti3SiC2 MAX phase/Polymethyl methacrylate metacomposites at radio-frequency region." Functional Materials Letters 12, no. 01 (2019): 1850101. http://dx.doi.org/10.1142/s1793604718501011.

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Metacomposites with negative permittivity have triggered tremendous fundamental and practical attention in recent years. In this paper, Ti3SiC2 MAX phase/Polymethyl methacrylate (PMMA) metacomposites with different Ti3SiC2 content were prepared. Weakly negative permittivity value (between [Formula: see text] and 0) was observed near percolation (Ti3SiC2 content of 60[Formula: see text]wt.%), attributing to moderate carrier concentration in Ti3SiC2 networks, and negative permittivity was tuned by tailoring conductive Ti3SiC2 networks. AC conductivity spectra and negative permittivity spectra of composites over percolation were explained by Drude model, indicating metal-like conduction behavior and low-frequency plasmonic oscillation in composites. The impedance response of composites was analyzed by equivalent circuit models, manifesting correspondence between inductor and negative permittivity. This work presented a new type of metacomposite constructed by Ti3SiC2 MAX phase and further revealed the generation mechanism of negative permittivity, which will greatly facilitate the practical applications of MAX phase in metacomposites.
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19

Sekine, Takashi, Takuya Hoshina, Song Min Nam, et al. "Dielectric Measurement of BaTiO3 Powder and Its Statistical Analysis." Key Engineering Materials 301 (January 2006): 251–56. http://dx.doi.org/10.4028/www.scientific.net/kem.301.251.

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Dielectric permittivity of BaTiO3 powders was determined by measuring permittivity of slurries prepared from BaTiO3 powder and propylene carbonate as dispersion medium followed by analyzing with a finite element methods (FEM). The permittivity of powders depended on their characters such as tetragonality (c/a ratio), density, particle size and specific surface area. In order to extract the effect of each character, a statistical analysis was carried out to represent the permittivity of powders with an empirical equation where the c/a ratio, density and particle size were used as parameters. A fairly good agreement between observed data and those estimated from the relation was obtained and the contribution of each character to the permittivity could be determined.
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20

Chen, Yan, and Li Bao An. "Electron Beam Irradiation on Substrate for Precise Dielectrophoretic Assembly of Carbon Nanotubes - A Simulation." Advanced Materials Research 960-961 (June 2014): 69–72. http://dx.doi.org/10.4028/www.scientific.net/amr.960-961.69.

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The effect of electron beam irradiation on permittivity of silicon dioxide insulate layer was investigated. Theoretical analysis indicates that electron beam irradiation will change the permittivity of SiO2through decreasing the molecular number per unit volume and increasing the polarizability of the sample. The escape of impurities during irradiation decreases the permittivity while the accumulation of space charge increases the permittivity. Simulation results show that with the change of permittivity, the electric field of the area irradiated by electron beam is strengthened locally and carbon nanotubes (CNTs) are more likely attracted to this area by dielectrophoresis. Therefore, the method could be used for precise positioning of CNTs for various applications in many areas including nanoelectronics, sensors, and new energies.
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21

Luo, Yongzhen, Xidong Ding, Tianci Chen, Guocong Lin, Tao Su, and Dihu Chen. "Imaging the Permittivity of Thin Film Materials by Using Scanning Capacitance Microscopy." Applied Sciences 12, no. 23 (2022): 11979. http://dx.doi.org/10.3390/app122311979.

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Recently, great advances had been made by using scanning probe microscopy (SPM) to quantify the relative permittivity of thin film materials on a nanometer scale. The imaging techniques of permittivity for thin film materials with SPM, especially for photoelectric materials, have not been fully researched until now. Here, we presented a method to image permittivity of thin film materials by using a scanning capacitance microscope (SCM). This method combined the quantitative measurement by using SCM with the capacitance gradient–distance fitting curve to obtain the two-dimensional (2D) permittivity image at room temperature under atmospheric conditions. For the demonstration, a 2D permittivity image of film of molybdenum oxide (MoO3), a kind of photoelectric material, was acquired. From the image, it could be found that the average values of permittivity of MoO3 film and of MoO3 film-doped NaCl were about 8.0 and 9.5, respectively. The experimental results were quantitatively consistent with other experimental results of the same material. The reported technique here could provide a novel method for imaging the relative permittivity with nanometer resolution and be helpful for the study of photoelectric materials.
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22

Lopez-Prades, Sandra, Mónica Torrecilla-Vall-llossera, Mercedes Rus, Miriam Cuatrecasas, and Joan M. O’Callaghan. "Integrating Complex Permittivity Measurements with Histological Analysis for Advanced Tissue Characterization." Sensors 25, no. 8 (2025): 2626. https://doi.org/10.3390/s25082626.

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We developed a measurement setup and protocol reliably relating complex permittivity measurements with tissue characterization and specific histological features. We measured 148 fresh human tissue samples across 14 tissue types at 51 frequencies ranging from 200 MHz to 20 GHz, using an open-ended coaxial slim probe. Tissue samples were collected using a punch biopsy, ensuring that the sampled area encompassed the region where complex permittivity measurements were performed. This approach minimized experimental uncertainty related to potential position-dependent variations in permittivity. Once measured, the samples were then formalin-fixed and paraffin-embedded (FFPE) to obtain histological slides for microscopic analysis of tissue features. We observed that complex permittivity values are strongly associated with key histological features, including fat content, necrosis, and fibrosis. Most tissue samples exhibiting these features could be differentiated from nominal values for that tissue type, even accounting for statistical variability and instrumental uncertainties. These findings demonstrate the potential of incorporating fast in situ complex permittivity for fresh tissue characterization in pathology workflows. Furthermore, our work lays the groundwork for enhancing databases where complex permittivity values are measured under histological control, enabling precise correlations between permittivity values, tissue characterization, and histological features.
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23

Zhuck, N. P., K. Sch¸nemann, and S. N. Shulga. "Effective Permittivity of a Statistically Inhomogeneous Medium with Strong Permittivity Fluctuations." Progress In Electromagnetics Research 44 (2004): 169–95. http://dx.doi.org/10.2528/pier03033001.

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24

Easton, C. D., M. V. Jacob, and J. Krupka. "Non-destructive complex permittivity measurement of low permittivity thin film materials." Measurement Science and Technology 18, no. 9 (2007): 2869–77. http://dx.doi.org/10.1088/0957-0233/18/9/016.

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25

Kato, Yuto, and Masahiro Horibe. "New Permittivity Measurement Methods Using Resonant Phenomena For High-Permittivity Materials." IEEE Transactions on Instrumentation and Measurement 66, no. 6 (2017): 1191–200. http://dx.doi.org/10.1109/tim.2017.2662558.

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26

Manaila-Maximean, Doina. "Effective Permittivity of a Multi-Phase System: Nanoparticle-Doped Polymer-Dispersed Liquid Crystal Films." Molecules 26, no. 5 (2021): 1441. http://dx.doi.org/10.3390/molecules26051441.

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This paper studies the effective dielectric properties of heterogeneous materials of the type particle inclusions in a host medium, using the Maxwell Garnet and the Bruggeman theory. The results of the theories are applied at polymer-dispersed liquid crystal (PDLC) films, nanoparticles (NP)-doped LCs, and developed for NP-doped PDLC films. The effective permittivity of the composite was simulated at sufficiently high frequency, where the permittivity is constant, obtaining results on its dependency on the constituents’ permittivity and concentrations. The two models are compared and discussed. The method used for simulating the doped PDLC retains its general character and can be applied for other similar multiphase composites. The methods can be used to calculate the effective permittivity of a LC composite, or, in the case of a composite in which one of the phases has an unknown permittivity, to extract it from the measured composite permittivity. The obtained data are necessary in the design of the electrical circuits.
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27

Olkkonen, Martta-Kaisa, Pekka Eskelinen, Eeva Huuskonen-Snicker, Terhi Pellinen, and Pablo Olmos Martinez. "An Evaluation of the Permittivity of Two Different Rock Types Using Microwave Resonator and Waveguide Cutoff Principles." Frequenz 69, no. 1-2 (2014): 75–82. http://dx.doi.org/10.1515/freq-2014-0040.

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Abstract Methods of measuring the complex permittivity of different rock types are demonstrated in the frequency range from 6 GHz to 17 GHz. The used methods are based on the cylindrical resonator and waveguide cutoff frequency principles. This study is part of a larger research project that aims to characterize the electrical properties of asphalt for road surveying purposes. The studied rock types are metavolcanic rock with intermediate composition and pegmatite. The permittivity values gained with the resonator method are 6.2 for the metavolcanic rock and 4.5 for the pegmatite rock type, whereas the imaginary parts are 0.04 and 0.02. The permittivity values gained with the cutoff frequency method are 6.17 and 4.76 respectively. A reference measurement was made only for the metavolcanic rock in a transmission configuration with two antennas and the permittivity result was 6.21. The three different methods provide consistent permittivity values and are suitable for reliable permittivity evaluation.
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28

Huang, Haoping, and Douglas C. Fraser. "Mapping of the resistivity, susceptibility, and permittivity of the earth using a helicopter‐borne electromagnetic system." GEOPHYSICS 66, no. 1 (2001): 148–57. http://dx.doi.org/10.1190/1.1444889.

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Interpretation of helicopter‐borne electromagnetic (EM) data is commonly based on the mapping of resistivity (or conductivity) under the assumption that the magnetic permeability is that of free space and dielectric permittivity can be ignored. However, the data obtained from a multifrequency EM system may contain information about the magnetic permeability and dielectric permittivity as well as the conductivity. Our previous work has shown how helicopter EM data may be transformed to yield the resistivity and magnetic permeability or, alternatively, the resistivity and dielectric permittivity. A method has now been developed to recover the resistivity, magnetic permeability, and dielectric permittivity together from the transformation of helicopter EM data based on a half‐space model. A field example is presented from an area which exhibits both permeable and dielectric properties. This example shows that the mapping of resistivity, magnetic permeability, and dielectric permittivity together yields more credible results than if the permeability or permittivity is ignored.
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29

Wang, Jiajia, Yunyu Gao, and Sherman Xuegang Xin. "Using the Probability Density Function-Based Channel-Combination Bloch–Siegert Method Realizes Permittivity Imaging at 3T." Bioengineering 11, no. 7 (2024): 699. http://dx.doi.org/10.3390/bioengineering11070699.

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Magnetic resonance electrical properties tomography (MR EPT) can retrieve permittivity from the B1+ magnitude. However, the accuracy of the permittivity measurement using MR EPT is still not ideal due to the low signal-to-noise ratio (SNR) of B1+ magnitude. In this study, the probability density function (PDF)-based channel-combination Bloch–Siegert (BSS) method was firstly introduced to MR EPT for improving the accuracy of the permittivity measurement. MRI experiments were performed using a 3T scanner with an eight-channel receiver coil. The homogeneous water phantom was scanned for assessing the spatial distribution of B1+ magnitude obtained from the PDF-based channel-combination BSS method. Gadolinium (Gd) phantom and rats were scanned for assessing the feasibility of the PDF-based channel-combination BSS method in MR EPT. The Helmholtz-based EPT reconstruction algorithm was selected. For quantitative comparison, the permittivity measured by the open-ended coaxial probe method was considered as the ground-truth value. The accuracy of the permittivity measurement was estimated by the relative error between the reconstructed value and the ground-truth value. The reconstructed relative permittivity of Gd phantom was 52.413, while that of rat leg muscle was 54.053. The ground-truth values of relative permittivity of Gd phantom and rat leg muscle were 78.86 and 49.04, respectively. The relative error of average permittivity was 33.53% for Gd and 10.22% for rat leg muscle. The results indicated the high accuracy of the permittivity measurement using the PDF-based channel-combination BSS method in MR EPT. This improvement may promote the clinical application of MR EPT technology, such as in the early diagnosis of cancers.
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30

Lee, Seojoo, and Ji-Hun Kang. "Gap-Size-Dependent Effective Phase Transition in Metasurfaces of Closed-Ring Resonators." Crystals 11, no. 6 (2021): 684. http://dx.doi.org/10.3390/cryst11060684.

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We theoretically investigate a metal-to-insulator transition in artificial two-dimensional (2D) crystals (i.e., metasurfaces) of tightly coupled closed-ring resonators. Strong interaction between unit resonators in the metasurfaces yields the effective permittivity highly dependent on the lattice spacing of unit resonators. Through our rigorous theory, we provide a closed form of effective permittivity of the metasurface and reveal that the permittivity possesses a Lorentzian-type resonant behavior, implying that the transition of the effective permittivity can arise when the lattice spacing passes a critical value.
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31

Robinson, D. A., C. M. K. Gardner, J. Evans, J. D. Cooper, M. G. Hodnett, and J. P. Bell. "The dielectric calibration of capacitance probes for soil hydrology using an oscillation frequency response model." Hydrology and Earth System Sciences 2, no. 1 (1998): 111–20. http://dx.doi.org/10.5194/hess-2-111-1998.

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Abstract. Capacitance probes are a fast, safe and relatively inexpensive means of measuring the relative permittivity of soils, which can then be used to estimate soil water content. Initial experiments with capacitance probes used empirical calibrations between the frequency response of the instrument and soil water content. This has the disadvantage that the calibrations are instrument-dependent. A twofold calibration strategy is described in this paper; the instrument frequency is turned into relative permittivity (dielectric constant) which can then be calibrated against soil water content. This approach offers the advantages of making the second calibration, from soil permittivity to soil water content. instrument-independent and allows comparison with other dielectric methods, such as time domain reflectometry. A physically based model, used to calibrate capacitance probes in terms of relative permittivity (εr) is presented. The model, which was developed from circuit analysis, predicts, successfully, the frequency response of the instrument in liquids with different relative permittivities, using only measurements in air and water. lt was used successfully to calibrate 10 prototype surface capacitance insertion probes (SCIPS) and a depth capacitance probe. The findings demonstrate that the geometric properties of the instrument electrodes were an important parameter in the model, the value of which could be fixed through measurement. The relationship between apparent soil permittivity and volumetric water content has been the subject of much research in the last 30 years. Two lines of investigation have developed, time domain reflectometry (TDR) and capacitance. Both methods claim to measure relative permittivity and should therefore be comparable. This paper demonstrates that the IH capacitance probe overestimates relative permittivity as the ionic conductivity of the medium increases. Electrically conducting ionic solutions were used to test the magnitude of this effect on the determination of relative permittivity. The response was modelled so that the relative permittivity, independent of ionic conductivity, could be determined in solutions with an electrical conductivity of up to 0.25 S m-1. It was found that a solution EC of less than 0.05 S m-1 had little impact on the permittivity measurement.
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32

Zhu, Hui, Chong Gao, En Li, Chengyong Yu, Xinjie Xu, and Junwen Pan. "Permittivity measurement of the substrate by using the corrected differential phase method and quick-press test fixture." Review of Scientific Instruments 93, no. 9 (2022): 094709. http://dx.doi.org/10.1063/5.0087780.

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Permittivity is critical for analyzing electromagnetic propagation in the substrate. The differential phase method is desirable to measure the permittivity of the substrate. The actual measurement is usually required to be started at a low frequency to avoid the S21-phase ambiguity problem. To get rid of this problem, the unwrapped S21-phase is calculated accurately at any measurement frequency range. In the classical method of calculating the real permittivity from the effective permittivity, the calculation error increases gradually with increasing frequency, especially in an ultra-wide frequency range. To effectively reduce the error, the ratio of the calculated and real permittivity is used in the permittivity correction, which is a function with respect to frequency, dimension, and permittivity of the microstrip line. A two-step fitting process is proposed to reduce the dimension of the ratio function from three-dimension to two-dimension. Furthermore, a quick-press test fixture is designed for a more convenient measurement, which is characterized by no soldering requirement and ultra-wide frequency range. Compared with the stripline resonant method, in the proposed method, the maximum deviations of the four substrates are 0.035, −0.04, 0.07, and 0.13, in the frequency range of 1–40 GHz.
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33

Trivedi, C. M., V. A. Rana, P. G. Hudge та A. C. Kumbharkhane. "Dielectric relaxation studies of binary mixture of β-picoline and methanol using time domain reflectometry at different temperatures". Journal of Advanced Dielectrics 06, № 03 (2016): 1650022. http://dx.doi.org/10.1142/s2010135x16500223.

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Complex permittivity spectra of binary mixtures of varying concentrations of [Formula: see text]-picoline and Methanol (MeOH) have been obtained using time domain reflectometry (TDR) technique over frequency range 10 MHz to 25 GHz at 283.15, 288.15, 293.15 and 298.15 K temperatures. The dielectric relaxation parameters namely static permittivity ([Formula: see text]), high frequency limit permittivity ([Formula: see text]) and the relaxation time ([Formula: see text]) were determined by fitting complex permittivity data to the single Debye/Cole-Davidson model. Complex nonlinear least square (CNLS) fitting procedure was carried out using LEVMW software. The excess permittivity ([Formula: see text]) and the excess inverse relaxation time (1/[Formula: see text] which contain information regarding molecular structure and interaction between polar–polar liquids were also determined. From the experimental data, parameters such as effective Kirkwood correlation factor (geff), Bruggeman factor (fB) and some thermo dynamical parameters have been calculated. Excess parameters were fitted to the Redlich–Kister polynomial equation. The values of static permittivity and relaxation time increase nonlinearly with increase in the mol–fraction of MeOH at all temperatures. The values of excess static permittivity ([Formula: see text]E) and the excess inverse relaxation time (1/[Formula: see text] are negative for the studied [Formula: see text]-picoline — MeOH system at all temperatures.
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34

Essingholt, Felix, Frederic Meyer, Peter Kuhn, Philip Schmidt, Thorsten Benkner, and Anton Grabmaier. "Non-Invasive Heart Beat Measurement Using Microwave Resonators." Proceedings 2, no. 13 (2018): 1002. http://dx.doi.org/10.3390/proceedings2131002.

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In this paper we present the first results of our research regarding microwave biosensors for non-invasive permittivity monitoring of the human body. To detect permittivity changes, resonators are used, which alter their resonance frequency and their quality factor depending on the permittivity of the material they are placed upon. These permittivity changes may be used as indicators for the heart rate, blood pressure or glucose level. As a proof of concept, this paper focusses on designing resonators to detect the heart beat of humans in the Radial Artery, which is located in the forearm.
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35

Li, Jianyong, Hirofumi Kakemoto, Satoshi Wada, and Takaaki Tsurumi. "Dielectric Spectra of BaTiO3-Based Ceramics Measured by Impedance Analyzer Using Micro Planar Electrodes." Key Engineering Materials 301 (January 2006): 129–34. http://dx.doi.org/10.4028/www.scientific.net/kem.301.129.

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A new measuring method and analyzing procedure were proposed to determine the complex dielectric permittivity of materials with relatively high permittivity using an RF-impedance analyzer. Samples used for the measurement were (Ba0.6Sr0.4)TiO3 and Ba(Zr0.25Ti0.75)O3 ceramics. Micro planar electrodes were used for the measurement of complex admittance of these samples. Electromagnetic simulations were carried out for determining the relative dielectric permittivity and dielectric loss. The complex dielectric permittivity vs. frequency curves of Ba(Zr0.25Ti0.75)O3 showed a broad dielectric relaxation, while that of (Ba0.6Sr0.4)TiO3 was almost flat up to 3 GHz.
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36

Xie, Zhenwen, Xingzao Chen, Jing Wang, and Jiaqi Chen. "Three-Dimensional Meso-Structure-Based Model for Evaluating the Complex Permittivity of Asphalt Concrete." Materials 17, no. 8 (2024): 1900. http://dx.doi.org/10.3390/ma17081900.

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Microwave heating is an emerging alternative pretreatment method for road maintenance in cold seasons. The thermal behavior of asphalt pavement under microwave heating is mainly determined by the complex permittivity of the asphalt mixture. In this study, an innovative approach for calculating the complex permittivity of an asphalt mixture based on a three-dimensional meso-scale heterogeneous structure was proposed. A series of experiments was conducted to verify the accuracy of this approach. The effect of porosity, void size, moisture content and aggregate gradation on the complex permittivity for an asphalt mixture were computationally analyzed based on the validated approach. Moreover, the applicability of commonly used classical dielectric models was analyzed. The classical Lichtenecker–Rother (LR) dielectric model was modified on the basis of simulation data for various conditions. The results showed that the real part of the complex permittivity decreased with the increase in porosity. Some sudden change in the imaginary part of the complex permittivity was observed within the frequency range from 2.6 GHz to 3.9 GHz. A larger air void size would lead to a larger frequency at which sudden change occurs. The real part and imaginary part of the complex permittivity tend to be smaller when more coarse aggregates are replaced with fine aggregates. Both the real part and the imaginary part of the complex permittivity increase with higher moisture content due to the stronger dielectric property of water. Each 1% increase in moisture content would lead to about a 3~4% increase in the real part of the complex permittivity. The determination coefficients R2 for the real part and the imaginary part of the complex permittivity fitted by the modified Brown model were the maximum values, which were 0.922 and 0.980, respectively. The method presented in this study is useful for transportation agencies to optimize microwave heating during winter maintenance.
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37

Jung, Gwang-Hun, SeokJae Yoo, and Q.-Han Park. "Measuring the optical permittivity of two-dimensional materials without a priori knowledge of electronic transitions." Nanophotonics 8, no. 2 (2018): 263–70. http://dx.doi.org/10.1515/nanoph-2018-0120.

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AbstractWe propose a deterministic method to measure the optical permittivity of two-dimensional (2D) materials without a priori knowledge of the electronic transitions over the spectral window of interest. Using the thin-film approximation, we show that the ratio of reflection coefficients for s and p polarization can give a unique solution to the permittivity of 2D materials within the measured spectral window. The uniqueness and completeness of our permittivity measurement method do not require a priori knowledge of the electronic transitions of a given material. We experimentally demonstrate that the permittivity of monolayers of MoS2, WS2, and WSe2 in the visible frequency range can be accurately obtained by our method. We believe that our method can provide fast and reliable measurement of the optical permittivity of newly discovered 2D materials.
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38

Mustata, Florin St C., and Adriana Mustata. "Dielectric Behaviour of Some Woven Fabrics on the Basis of Natural Cellulosic Fibers." Advances in Materials Science and Engineering 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/216548.

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The electrical permittivity of the weaves obtained from natural cellulosic yarns or mixed with synthetic fibers was established with capacitor method. The highest value of relative electrical permittivity in case of the woven fabric from natural cellulosic fibers has been observed at the weave made of pure hemp (13.55) and the lowest at the weave obtained from the pure jute—weave packing (1.87). Electrical permittivity value of the pure jute weave packing is comparable to that of the permittivity for the glass thread, when the work conditions are as follows: temperature 25°C and air humidity 35%. The relative electrical permittivity of the weave is depending on the degree of crimping yarns especially in the weft direction, technological density in direction of the warp and weft, and surface mass of the weave.
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39

Ouhassan, Youssef, Seddik Bri, and Mohamed Habibi. "Complex permittivity of FeSiAl/Al2O3 ceramic composite at X-band frequencies." E3S Web of Conferences 297 (2021): 01013. http://dx.doi.org/10.1051/e3sconf/202129701013.

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The objective of this paper is to extract and study the complex permittivity of the FeSiAl/Al2O3 ceramic composite at X-band frequencies. We studied by simulation the complex permittivity of four composites with FeSiAl content varying from 0% to 15% by volume in the alumina matrix. The influence of the FeSiAl content on the complex permittivity of the FeSiAl / Al2O3 composite was also studied. The results obtained show on the one hand that the complex permittivity depends on the frequency. Indeed, the values of the real and imaginary parts of the complex permittivity decrease with the increase in frequency over the entire frequency range in the X band. On the other hand, the high FeSiAl content has a significant impact on the values of the real and imaginary parts of complex permittivity. Higher values were obtained for composites with a high inclusion content. In this work, we obtained a good agreement between the simulation results and the published experimental results. These results indicate that the FeSiAl / Al2O3 composite can be used in applications as an electromagnetic wave absorbing material.
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40

Folgerø, Kjetil, Kjetil Haukalid, Jan Kocbach, and Andreas Soto Peterson. "Combined Thickness and Permittivity Measurement of Thin Layers with Open-Ended Coaxial Probes." Sensors 19, no. 8 (2019): 1765. http://dx.doi.org/10.3390/s19081765.

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This paper presents a method to simultaneously determine the thickness and permittivity of thin layers from multi-frequency reflection coefficient measurements using an open-ended coaxial probe. This is achieved by exploiting that the probe becomes radiating at frequencies higher than the probe’s typical operating range. Permittivity information is extracted from measurements in the typical frequency range, whereas thickness information is obtained from high frequency measurements by exploiting resonances that occur when the radiated waves are reflected at the layer boundary. A finite element model of the measurement set-up is made in COMSOL MultiphysicsTM, and a matrix of simulations spanning the relevant layer thicknesses and permittivity range is generated. The measured permittivity spectra of unknown samples are compared to the simulation matrix to estimate layer thickness and permittivity. The method is verified by measurements of water–ethanol mixtures. An application example where the water fraction and layer thickness of a gas hydrate deposition layer is estimated from permittivity measurements in a multiphase flow loop is also presented.
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41

Rowe, R. K., J. Q. Shang, and Y. Xie. "Complex permittivity measurement system for detecting soil contamination." Canadian Geotechnical Journal 38, no. 3 (2001): 498–506. http://dx.doi.org/10.1139/t00-117.

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The design, calibration, and operation of a laboratory-scale system to assess the viability of detecting contaminants in soil based on changes in its electromagnetic response are described. The complex permittivity measurement device, permeation apparatus, and dielectric responses of soil specimens measured before and after permeation with different CaCl2 solutions are discussed. It is shown that the change in the complex permittivity of the soil is best characterized in terms of the permittivity and loss factor at the frequency of 250 MHz, since they exhibit a significant response to changes in the pore-fluid chemistry. The laboratory system can be used routinely to create soil samples permeated with a known contaminant at known concentrations and then measure the complex permittivity of the contaminated soil samples directly after permeation. The system is such that other factors (e.g., density and water content) which could influence the complex permittivity can be carefully controlled, allowing the relationship between the type and level of contamination and dielectric behaviour of soils to be established.Key words: complex permittivity, nondestructive testing, soil contamination, detection of soil contamination, environmental technology.
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42

Rowe, R. K., J. Q. Shang, and Y. Xie. "Effect of permeating solutions on complex permittivity of compacted clay." Canadian Geotechnical Journal 39, no. 5 (2002): 1016–25. http://dx.doi.org/10.1139/t02-051.

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The complex permittivity of a natural clayey till (Halton Till) is measured before and after permeating with four different ionic contaminant solutions (CaCl2, MgCl2, NaCl, and acetic acid) to examine the effects of contaminant type and concentration on the complex permittivity of contaminated soil. The complex permittivity at 250 MHz is most sensitive to the concentration of the ions in the pore fluid, and a good linear correlation is obtained between the real and the imaginary parts of the complex permittivity and the concentrations of the anions, including chloride and acetate. These anions are distinguished by their own unique relationships for the simple solutions examined. Linear relationships also exist between the real and the imaginary parts of the complex permittivity and all of the cation species in the simple chloride salt solutions, namely Ca2+, Mg2+, and Na+. The results provide the evidence that the complex permittivity of soils may be used to identify changes in soil pore-water chemistry. As such, it may have potential for use in the detection of soil contamination.Key words: environmental, dielectric, detection, contamination, waste management.
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43

Matković, Anđela, and Antonio Šarolić. "The Effect of Freezing and Thawing on Complex Permittivity of Bovine Tissues." Sensors 22, no. 24 (2022): 9806. http://dx.doi.org/10.3390/s22249806.

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The aim of this study was to investigate how the freezing and thawing of biological tissues affect their complex permittivity in the microwave frequency range from 0.5 MHz to 18 GHz. We measured the complex permittivity of ex vivo bovine tissues, including brain white and grey matter, liver, and muscle, using an open-ended coaxial probe. Bovine tissues were chosen for their availability and similarity to human tissue permittivity. The samples were measured at 25 °C, before they were frozen either in a commercial freezer below −18 °C or in liquid nitrogen, nominally at −196 °C. The measured permittivity before freezing was compared to the permittivity measured after freezing and thawing the tissues back to 25 °C. Statistical analysis of the results showed a statistically significant change in permittivity after freezing and thawing by both methods for all the measured tissues, at least in some parts of the measured frequency range. The largest difference was observed for the white matter, while the liver had the smallest percent change.
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44

Du, Erji, Lin Zhao, Guojie Hu, et al. "A Soil Refractive Index (SRI) Model Characterizing the Functional Relationship Between Soil Moisture Content and Permittivity." Water 17, no. 3 (2025): 399. https://doi.org/10.3390/w17030399.

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The functional relationship between soil permittivity and soil water content serves as the theoretical foundation for electromagnetic wave-based techniques used to determine soil moisture levels. However, the response of permittivity to changes in soil water content varies significantly across different soil types. Current models that utilize soil permittivity to estimate soil water content are often based on empirical statistical relationships specific to particular soil types. Moreover, existing physical models are hindered by an excessive number of parameters, which can be difficult to measure or calculate. This study introduces a universal model, termed the Soil Refractive Index (SRI) model, to describe the relationship between soil permittivity and soil water content. The SRI model is derived from the propagation velocity of electromagnetic waves in various soil components and the functional relationship between electromagnetic wave velocity and relative permittivity. The SRI model expresses soil water content as a linear function of the square root of the relative permittivity for any soil type with the slope and intercept as the two undetermined parameters. The slope is primarily influenced by the relative permittivity of soil water, while the intercept is mainly affected by both the slope and the soil porosity. The applicability of the SRI model is validated through tested soil samples and comparison with previously published empirical statistical models. For dielectric lossless soil, the theoretical value of the slope is calculated to be 0.126. The intercept varies across different soil types and increases linearly with soil porosity. The SRI model provides a theoretical basis for calculating soil water content using permittivity across various soil types.
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45

Guo, Hong Fu, Chao Xu, Cai Xiang Xu, and Gui Hua Gao. "A New Measuring Method of the Relatively Permittivity Based on Antenna's Resonant Characteristics." Applied Mechanics and Materials 475-476 (December 2013): 95–98. http://dx.doi.org/10.4028/www.scientific.net/amm.475-476.95.

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This paper proposes a matter of permittivity measurement method which based on the microwave antennas resonant characteristics. The basic principle of measuring permittivity was analyzed by the antenna resonance theory. The simulation model has been build and analyzed by Ansoft HFSS simulation software. The relationship between different permittivity and the antennas resonant frequency was given. The experimental model was designed and the experimental data of sample was measured. The experimental and simulation data are compared and discussed. Results show that the simulation and experimental results are consistent well; the antenna resonance method to measure the permittivity is feasible.
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46

Trivedi, Chintan M., Vipinchandra A. Rana, and Hemantkumar A. Chaube. "Microwave Dielectric Relaxation in Binary Mixtures of Pyridine and 1-Propanol at Different Temperatures." Solid State Phenomena 209 (November 2013): 86–89. http://dx.doi.org/10.4028/www.scientific.net/ssp.209.86.

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Dielectric constant (ε′) and Dielectric loss (ε″) of the binary mixtures of the pyridine and 1-propanol have been measured at microwave frequencies of X-band and J-band at 303,313 and 323K temperatures. Static dielectric permittivity (ε0) of the liquid samples has been determined using precision LCR meter. Dielectric permittivity at optical frequency (ε∞) has also been measured. Determined values of Static dielectric permittivity (ε0) and complex permittivity (ε*) at 9.1 GHz frequency were used to evaluate relaxation time (τ). Determined parameters have been interpreted in terms of molecular interaction among the molecular species of the binary mixtures.
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47

Krylov, V. P. "Determination of the permittivity of materials in a volume resonator with allowance for the surface roughness." Industrial laboratory. Diagnostics of materials 87, no. 5 (2021): 43–46. http://dx.doi.org/10.26896/1028-6861-2021-87-5-43-46.

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The accuracy of determining the permittivity of the material depends on the thickness of the intermediate layer with variable dielectric characteristics formed on the surface of the sample upon manufacturing. We present the results of studying the influence of the surface roughness of the test sample on the accuracy of determining the permittivity using the resonator method. An algorithm for calculating the permittivity in a volumetric cylindrical resonator is proposed, taking into account the roughness value and the residual gap. Using the matrix method for calculating the wave transmitted through the plate, a model for determination of the dielectric permittivity of a multilayer sample using a measuring resonator is developed. The results obtained can be used to improve the accuracy of the permittivity determination in a volume resonator when testing the samples with a roughness exceeding the required standard.
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48

KIM, JAE-SIK, EUI-SUN CHOI, YOUNG-HIE LEE, and KI-WON RYU. "STRUCTURAL AND RF PROPERTIES OFCo2ZFERRITE FOR ANTENNA SUBSTATE." Modern Physics Letters B 23, no. 31n32 (2009): 3731–37. http://dx.doi.org/10.1142/s0217984909021764.

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The sintering behavior and high frequency electro-magnetic properties of Ba3Co2Fe24O41ceramics were investigated for the small antenna application. All samples of the Ba3Co2Fe24O41ceramics were prepared by the solid-state reaction method and sintered at 1150°C 1400°C. From the XRD patterns of calcined Ba3Co2Fe24O41powders, the most suitable condition for calcining was 600°C–1000°C. Ba3Co2Fe24O41phase was observed in sintered Ba3Co2Fe24O41ceramics as main phase. Bulk densities increased with sintering temperature and decreased at 1400°C. Permittivity and permeability of the Ba3Co2Fe24O41ceramics increased or decreased with sintering temperature, respectively. On the other hand, loss tangent of permittivity and of permeability showed contrary tendency with permittivity and permeability. The permittivity and loss tangent of permittivity of Ba3Co2Fe24O41ceramics sintered at 1300°C were 19.896 and 0.171 at 210 MHz. and the measured value of permeability and loss tangent of permeability were 14.218 and 0.204, respectively.
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49

Bakry, Mostafa, and Ludger Klinkenbusch. "Using The Kramers-Kronig Transforms To Retrieve The Conductivity From The Effective Complex Permittivity." Advances in Radio Science 16 (September 4, 2018): 23–28. http://dx.doi.org/10.5194/ars-16-23-2018.

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Abstract. While measuring the effective permittivity of dispersive material it may be of interest to distinguish between conductivity losses (caused by free electrons) and dielectric losses (caused by bounded electrons) which both are included in the imaginary part. This usually turns out to be a non-trivial task unless suitable dispersion models for the dielectric and/or the conductivity properties of the material are assumed. In this paper we present a more general method based on the Kramers-Kronig transformations to separate the conductivity from the effective complex permittivity of a dispersive material. The Kramers-Kronig transforms (or KK-transforms) are unique integral relations between the real and the imaginary part of a complex quantity describing a causal system. The proposed method and the corresponding algorithm are tested by first supposing some fictitious values of the complex permittivity satisfying the KK-transforms. Then, different values of a conductivity are added leading to a change of the imaginary part of the effective permittivity while the real part remains the same. The effective permittivity (including a conductivity part) does generally not satisfy the KK-transforms. This fact will be employed to retrieve the conductivity from that effective complex permittivity. Finally the method is applied to measured values found in the literature to retrieve the conductivity from the effective permittivity of composite material.
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50

Khouni, Habib, and Nacerdine Bouzit. "Study of the relaxation and resonance behaviors of ternary composites: Epoxy–strontium titanate–carbon black." Polymers and Polymer Composites 28, no. 7 (2019): 451–61. http://dx.doi.org/10.1177/0967391119887573.

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The principal subject of the present article is the study of the phenomenon of dispersion as well as the effect of the concentration of strontium titanate (SrTiO3) and carbon black on the complex permittivity of ternary composites: epoxy resin–SrTiO3 –black carbon. The relative permittivity of the mixtures as a function of volume fraction of SrTiO3 was modeled by the modified Lichtenecker mixing law (MLL). A new dispersion model, based on the Lorentzian resonance model, has been proposed to describe the frequency behavior of complex permittivity. For these ternary composites, the frequency dispersion behavior of the complex permittivity that exhibits both relaxation and resonance spectra with increasing SrTiO3 concentration has been showed. The new empirical equation proposed in our work has been well describing the complex permittivity of resonance type for the SrTiO3 and carbon black composites. The effects of SrTiO3 content on the electromagnetic properties and absorption characteristics of electromagnetic waves of epoxy resin composites were studied. As the volume fraction of SrTiO3 increases, it was confirmed that the complex permittivity of the composites follows the MLL and the resonant frequency shifted toward the high frequency range. The resonance frequency of the composites was estimated in good agreement with the theoretical values calculated by the second new equation proposed in this article. Complex permittivity is measured using time domain spectroscopy in the frequency range direct current (DC) to 30 GHz.
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