The cavity perturbation method for evaluating hematocrit via dielectric properties

A cavity technique based on frequency shift was used to measure dielectric properties (dielectric constant and loss factor) of some particulate materials as a function of temperature. The materials studied were alumina, cobalt/alumina, dolomite, and sand. The properties were measured at various points between room temperature and 600 degrees C in the frequency range of 925-995 MHz. The dielectric constant and loss factor of all samples, except the cobalt/alumina catalyst sample, were approximately constant with temperature. The dielectric constant and loss factor of the cobalt/alumina sample exhibited a noticeable increase with temperature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The dielectric properties (components of the complex permittivity relative to free space) of ground hard red winter wheat of 11–25% moisture content were determined by dielectric spectroscopy measurements with an open-ended coaxial-line probe and impedance analyser over the frequency range from 10 MHz to 1.8 GHz at temperatures from 5 to 95 °C. Both the dielectric constant and dielectric loss factor, over the stated range of variables, decreased with increasing frequency and increased with increasing moisture content and temperature. Plots of the dielectric constant and loss factor in the complex permittivity plane revealed a linear relationship between the two permittivity components at frequencies above 1 GHz, but they showed nonlinearity at lower frequencies due to the increasing influence of ionic conduction as confirmed by Cole–Cole plots of the permittivity data.

Dielectric Properties of Uncooked Chicken Breast Muscles from Ten to One Thousand Eight Hundred Megahertz

Analysis of dielectric properties of soy sauce

The use of microwave energy is of growing interest due to brief time, volumetric heating due to its penetration and reduced processing time, making it an attractive source of thermal energy. The main objective of the present work is to study the effect of milk and tomato, strawberries juices temperatures and moisture contents, dry basis, on dielectric constant, loss tangent, loss factor and penetration depth at 2450 MHz affecting heat and mass transfer by microwave. It was found that the dielectric constant increased by increasing moisture contents, temperatures and increasing the ability of material to store energy. Dielectric constant and dielectric loss factor are exponentially satisfied with coefficients of determinations between0.84-0.91 for tomato and strawberries. The dielectric constant of milk satisfied a linear form with coefficients of determinations between 0.88-0.97. The loss tangent is deceased with increasing the moisture content indicating the energy lost or dissipated by the material, and satisfied a power form with coefficients of determinations ranged between0.75-0.98 for all tested materials.

Poly(p-phenylenediazomethine) was synthesized by the condensation reaction between glyoxal and p-phenylene diamine in different solvents like methanol, toluene, m-cresol and N,N-dimethylformamide. The dielectric properties and microwave conductivity of the pelletized samples were measured using cavity perturbation technique. The measurements were done at 2.17 GHz at room temperature (25°C). The effect of dopants on the dielectric properties and conductivity was studied using HCl and HClO4. Dielectric properties like dielectric constant, dielectric loss factor and microwave conductivity increased on doping with HCl and HClO4. Conducting polymer composites were prepared by in situ polymerization of glyoxal and p-phenylenediamine in different solvents containing different amounts of PVC, and silica. The microwave conductivity and complex permittivity of each sample was measured. The effect of dopants like HClO4 and HCl on these dielectric properties was also studied. The d.c. conductivity of the pressed samples measured by the two-probe method was also studied.

A six-port reflectometry (SPR) system was developed to predict the dielectric properties of both tumor and normal breast tissue, intended for medical diagnostic applications. Ensuring precise measurements, the SPR underwent calibration using a well-established four-step procedure, which will be briefly outlined. Afterward, the investigated coaxial probe was connected to the SPR through the calibrated measurement port. Subsequently, the exposed end of the probe aperture was immersed into synthetic samples representing both healthy and cancerous breast tissue to assess the dielectric constant, εrʹ and loss factor, εrʺ across frequencies ranging from 1.5 GHz to 3.3 GHz. The dielectric constant, εrʹ and loss factor, εrʺ were derived from the measured reflection coefficient using a closed-form equation associated with the coaxial probe. An examination was undertaken to compare the performance of a commercially available vector network analyzer (VNA) outfitted with a Keysight 85070E dielectric probe against an SPR-probe system. The comparison was based on analyzing the reflection coefficient magnitude, phase shift, dielectric constant, and loss factor of synthetic breast tissue samples. The study revealed maximum absolute errors of 0.01, 1.07°, 1.12, and 0.75 for the measured reflection coefficient magnitude, phase shift, dielectric constant, and loss factor, respectively. The calibrated reflection coefficient and predicted relative permittivity, εr can be effectively utilized to distinguish between normal (εrʹ &lt; 50) and tumor (εrʹ &gt; 50) breast tissue.

The dielectric properties of blackberry samples with a 20.0–80.0 % w.b (web basis) moisture content were determined with a network analyzer and an open-ended coaxial-line probe over a frequency range from 5 to 3000 MHz and a temperature range from 20 to 100 °C. The results showed that the dielectric constant decreased with increasing temperature but increased with increasing moisture content; however, the loss factor increased with increasing temperature and moisture content. The dielectric constant and the loss factor decreased with increasing frequency. The penetration depth decreased with increasing temperature, frequency and moisture content. A large penetration depth at 915 MHz may provide practical large-scale dielectric drying for blackberries. The dielectric constants and loss factors for blackberry by combining the above mathematical model and temperature and moisture of the sample in the microwave drying process were used to analyze and control blackberry drying technology.

Dielectric characterization of rapeseed (Brassica napus L.) from 10 to 3000 MHz

Dielectric properties of salmon ( Oncorhynchus keta) and sturgeon ( Acipenser transmontanus) caviar at radio frequency (RF) and microwave (MW) pasteurization frequencies

Dielectric properties of four small-sized watermelon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and an impedance analyser over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of the melons and also on tissue samples from the edible internal tissue. Moisture content and soluble solids content (SSC) were measured for internal tissue samples, and SSC (sweetness) was used as the quality factor for correlation with the dielectric properties. Individual dielectric constant and loss factor correlations with SSC were low, but a high correlation was obtained between the SSC and permittivity from a complex-plane plot of dielectric constant and loss factor, each divided by SSC. However, SSC prediction from the dielectric properties by this relationship was not as high as expected (coefficient of determination about 0.4). Permittivity data (dielectric constant and loss factor) for the melons are presented graphically to show their relationships with frequency for the four melon cultivars and for external surface and internal tissue measurements. A dielectric relaxation for the external surface measurements, which may be attributable to a combination of bound water, Maxwell–Wagner, molecular cluster or ion-related effects, is also illustrated. Coefficients of determination for complex-plane plots, moisture content and SSC relationship, and penetration depth are also shown graphically. Further studies are needed for determining the practicality of sensing melon quality from their dielectric properties.

The dielectric relaxation of benzyl alcohol substitutents (benzyl alcohol, m -methylbenzyl alcohol and m -nitrobenzyl alcohol) with methyl methacrylate and butyl methacrylate in dilute solution of carbon tetrachloride is measured at 9.37 GHz using Frequency domain (X-band) technique. Different dielectric parameters like dielectric constant (e׳), dielectric loss factor (e״) at Microwave frequency, static dielectric constant (e 0 ) and dielectric constant at infinite dilution (e ∞ ) at optical frequency have been determined. From the measured dielectric data, the relaxation time (t) calculated using Higasi method and activation energies (∆F t and ∆F η ) have been determined. All the dielectric parameters that are vary with the substitutent change in benzyl alcohol and chain length of acrylic esters. Suggests that, the proton donating ability is varying with the substitution of benzyl alcohol and proton accepting ability is varying with the chain length of acrylic esters. The relaxation time and molar free energy activation of 1:1 molar ratio is greater than other higher molar ratios (i.e. 3:1, 2:1, 1:2, 1:3) confirm that the existence of most likely 1:1 complex formation between the studied systems and also complex formation formed between free hydroxyl group of substituted benzyl alcohols and carbonyl group of acrylic esters (MMA and EMA).

Dielectric properties [dielectric constant (ε′) and loss factor (ε″)] of 8% and 10% (w/v) bentonite pastes at 2450 MHz were measured from - 25C to 90C by the cavity perturbation technique. the dielectric constant decreased as moisture content decreased and temperature increased (temperature ≤ OC). the relationships between loss factor, moisture content, and temperature were not straightforward due to the ionic loss (d.c. conductivity). Because of the similarities between bentonite pastes and most food materials in dielectric constant, loss factor, and penetration depth, bentonite pastes can be good model food systems to study microwave heating.

The reflection coefficient of water layer placed on mercury has been measured at a wave length 9.8 cm. and at 5.5°C. From the curve of reflection coefficient vs. thickness of the water layer, dielectric constant and loss factor (or refractive index and absorption coefficient) have been calculated according to the procedure described previously. Water has shown anomalous dispersion and absorption at this wave length. The dielectric constant and loss factor have been measured for ebonite, bakelite and methacryl resin at the same wave length, by the transmission method.

This paper presents an experimental and analytical study of irreversible change in piezoelectric wafer active sensor (PWAS) electromechanical (E/M) impedance and admittance signature under high temperature exposure. After elevated to high temperatures, change in the material properties of PWAS can be quantified through irreversible changes in its E/M impedance and admittance signature. For the experimental study, circular PWAS transducers were exposed to temperatures between 50 °C and 250 °C at 50 °C intervals. E/M impedance and admittance data were obtained before and after each heating cycle. Irreversible temperature sensitivity of PWAS resonance and anti-resonance frequency was estimated as 0.0246 kHz °C−1 and 0.0327 kHz °C−1 respectively. PWAS transducer material properties relevant to impedance or admittance signature such as dielectric constant, dielectric loss factor, mechanical loss factor, and in plane piezoelectric constant were determined experimentally at room temperature before and after the elevated temperature tests. The in-plane piezoelectric coefficient was measured by using optical-fiber strain transducer system. It was found that the dielectric constant and in-plane piezoelectric coefficient increased linearly with temperature. Dielectric loss also increases with temperature but remains within 0.2% of initial room temperature value. Change in dielectric properties and piezoelectric constant may be explained by depinning of domains or by domain wall motion. The piezoelectric material degradation was investigated microstructurally and crystallographically by using scanning electron microscope and x-ray diffraction method respectively. There were no noticeable changes in microstructure, crystal structure, unit cell dimension, or symmetry. The degraded PWAS material properties were determined by matching impedance and admittance spectrums from experimental results with a closed form circular PWAS analytical model. Analytical results showed that impedance and admittance strongly depend on elastic coefficient, dielectric constant, mechanical loss factor, dielectric loss tangent and in plane piezoelectric constant. These properties were found to be susceptible to change after high temperature exposure.