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The complex electric permittivity of Baijiu (one of the most consumed beverages) is measured over a frequency range of 2 to 20 GHz using a low-cost open-ended coaxial probe and a portable microwave analyzer. The Cole-Cole equation is used to fit the permittivity data, and the parameter values related are extracted using the particle swarm optimization. A linear relationship is obtained between these parameters and the alcohol by volume. A strong dependence of the permittivity on the alcohol content is also observed for other alcoholic drinks, including brandy and whisky. The study demonstrates that the microwave technique provides an efficient solution in the effort to determine the alcohol content and the principal component analysis is a powerful tool for the quick estimation of the dielectric properties. The sensor presented can contribute to efficient on-site quality control of alcoholic drinks. PRACTICAL APPLICATION: The microwave approach presented could offer an economical approach for the characterization of Baijiu and a general solution to the alcohol content determination for the alcoholic drinks industry., (© 2021 Institute of Food Technologists®.)

A new approach for the detection of cracks in a tooth is presented using a microwave coaxial sensor. In the test, the probe tip is in close contact with the tooth surface, and the fringe electromagnetic fields interact with the tooth. The presence of any crack affects the effective permittivity, causing changes in the signal received. Cracks in two representative teeth are evaluated. Low signal power was applied during the scan, and no heating effect was produced. From the scanning of the positions right on and away from the cracks, significant differences are seen in the magnitude and phase of the reflection coefficient. By comparison, it is found that better performance can be achieved using the phase at a high frequency. The probe is also used for permittivity determination. The permittivity of the crown is computed using the error correction technique, and the data are used in further modelling. In the analysis, the phase greatly changes when the thickness of the dielectric layer is below the aperture diameter. Thus, the characteristic of the limited signal penetration is revealed, enabling local inspection and accurate identification. With a simplified geometric model, it is shown that the air gap between the probe tip and the tooth surface does not contribute much to the whole sensing volume. In addition, there is close correlation between the extent of the crack and the phase, suggesting the potential for quantitative characterisation. The methodology proposed here could provide an alternative solution to efficient non-destructive detection of cracked teeth. [ABSTRACT FROM AUTHOR]

Microwave non-destructive testing has received extensive attention in recent years owing to its advantages of non-contact inspection, no need for a coupling medium or sensors attached on the object surface, a relatively easy measurement setup and no ionising radiation hazards. As an alternative method, it has been used for monitoring and evaluation of the structural integrity of glass fibre-reinforced polymer composite structures. This paper provides a comprehensive overview of the microwave-based techniques for composites, including material characterisation, strain sensing, near-field and far-field damage detection, and microwave-based thermography. Discussions on the research trends are presented. [ABSTRACT FROM AUTHOR]

Focuses on a study which proposed a microwave and thermal method to model high-power ferrite devices. Description of the microwave finite-element analysis; Discussion on the operating regions of magnetic loss that must be avoided; Investigation of the thermal characteristics of a differential phase shift ferrite-loaded waveguide; Calculations for selected bias field.

A linked static/microwave finite element solver for the analysis of ferrite-loaded waveguides with arbitrary geometry and magnetization is described. The magnetostatic solution of the DC bias circuit and ferrite magnetization curve are used to construct the tensor permeability for the microwave solver. This avoids using normalized tensor entries or demagnetizing fields and it caters for non-uniform bias fields. Split phase constants and a higher-order mode diagram are presented for the case of a quasi-planar stripline edge mode phase shifter. Field plots illustrate the edge mode phenomena. Copyright © 1999 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a detailed investigation of the electromagnetic (EM) properties of carbon fibre-reinforced polymer composites (CFRP) is presented. The electric permittivity, electrical conductivity, signal penetration and microwave absorption are discussed. Unidirectional composite laminate samples were characterised over X band (8–12 GHz) using the microwave transmission line technique. It is shown that the real part of the permittivity of the composites is not significantly anisotropic whereas the imaginary part is highly anisotropic. More microwave energy is reflected in the parallel case, while more energy is absorbed in the orthogonal case. These experimental results are studied at three geometric levels: macro-meso scale (laminate/lamina level) relating to lay-up and fibre direction dependence, microscale (fibre level) relating to the real part of the permittivity and nanoscale level relating to the imaginary part of the permittivity. The findings can contribute to improved design of carbon fibre composites for electromagnetic applications, like shielding, curing and non-destructive inspection. [ABSTRACT FROM AUTHOR]

The microwave transmission line technique is presented as an effective method for the evaluation of honey for the first time. The electrical permittivity is an intrinsic parameter of a material that can be used as an index of added water content. For the permittivity calculation, it is found that the combination of the characteristic matrix method and Tischer’s model can offer the highest accuracy. A genetic algorithm is introduced to provide an initial approximate permittivity value and acquire the Cole-Cole parameters of the honeys examined. The accuracy provided by the methodology used in this study is superior to that offered by a commercially available probe. Operating at room temperature and a frequency range of 6–8 GHz, the measurements demonstrate that the permittivity of honey increases with increased added water. A relationship between the added water content and the permittivity of honey-water mixture is established, which could be a powerful tool for detecting honey adulteration. [ABSTRACT FROM AUTHOR]