Evaluation of Microwave Applicator Design on Electromagnetic Field Distribution and Heating Pattern of Cooked Peeled Shrimp

Non-uniform temperature distribution within solid food is a major problem associated with microwave heating, which limits industrial applications. Therefore, an experimentally validated 3D model was proposed to study the effect of microwave applicator geometry on the electromagnetic field distribution and heating pattern of shrimp under different processing conditions. Simulation results were compared with physical experiments, in which a cooked peeled shrimp sample was heated using two different laboratory-scale microwave applicators (rectangular and cylindrical cavities). For the rectangular applicator, the temperature distribution within the shrimp, when examined in cross-section, was more homogeneous compared to that of the cylindrical applicator. The results showed the influence of the complex shape of the food on the temperature distribution during microwave heating, as well as of process parameters (input power and geometry cavity). Moreover, this modelling method could provide a better understanding of the microwave heating process and assist manufacturing companies to evaluate a suitable microwave applicator according to their specific purpose.

Theoretical Study of the Input Impedance and Electromagnetic Field Distribution of a Dipole Antenna Printed on an Electrical/Magnetic Uniaxial Anisotropic Substrate

The present work considers the investigation of the effects of both electrical and magnetic uniaxial anisotropies on the input impedance, resonant length, and fields distribution of a dipole printed on an anisotropic grounded substrate. In this study, the associated integral equation, based on the derivation of the Green’s functions in the spectral domain, is numerically solved employing the method of moments. In order to validate the computing method and the evaluated calculation code, numerical results are compared with available data in the literature treating particular cases of electrical uniaxial anisotropy; reasonable agreements are reported. Novel results of the magnetic uniaxial anisotropy effects on the input impedance and the evaluated electromagnetic field are presented and discussed. This work will serve as a stepping stone for further works for a better understanding of the electromagnetic field behavior in complex anisotropic and bi-anisotropic media.

Features of field modeling of electromagnetic processes of trolley busbar

Purpose. Research and analysis trolley busbar’s parameters in condition of higher current harmonic actions, with taking into account the structural features of nonlinearity of magnetic and electrical properties of materials, proximity effects, surface and external surface effects. Methodology. The researches were carried out using the electromagnetic field theory methods, the electrical circuit theory, mathematical physics, finite elements, interpolation, approximation and regression analysis. Findings. The mathematical spatial model of electromagnetic processes in a steel trolley busbar in time statement of a problem of distribution of an electromagnetic field is developed. The dependences of the distribution of equipotential lines of the resulting z-component of the magnetic potential vector along the busbar, as well as the distribution of the resulting normal component of magnetic induction and magnetic field strength in the transverse (XY) cross section at non-sinusoidal current in busbar trolleys is obtained. Along the length of the busbar, in their cross section, the magnetic field tends to a plane-parallel shape it is proved. The error of the modulus of the vector magnetic potential along the length of the busbar does not exceed 0.9-1.2%. To reduce the dimension of the problem, computational resources and calculation time, a two-dimensional plane-parallel mathematical model in the frequency setting of the electromagnetic field distribution is proposed. To take into account the nonlinear magnetic properties of steel trolleys, to determine the effective magnetization curve for the nonlinear two-dimensional problem of the electromagnetic field of the busbar it is proposed. The verification results, according to the calculated voltage drop, confirm the high accuracy of the calculation and the reliability of the obtained results (error does not exceed 1.88% ÷ 2.06%) of the two-dimensional model in the frequency setting relative to the spatial model in the problem of time-dependent electrical -magnetic field is obtained. Originality. A mathematical two-dimensional model of electromagnetic processes in the frequency formulation of the problem of electromagnetic field distribution in a trolley busbar is proposed, which takes into account design features, nonlinearity of magnetic and electrophysical properties of materials, proximity effects, surface and external surface effects, influence of harmonic current components power transmission, which allows with high accuracy and efficiency of numerical implementation to determine the parameters of the bus trolls for the corresponding values of the amplitudes and frequencies of the frequencies harmonics of the current. Practical value. Verification of the calculated voltage drop confirms the high accuracy of the calculation and the reliability of the results (error does not exceed 1.88% ÷ 2.06%) of the two-dimensional model in the frequency reference relative to the spatial model in the problem of time-dependent electromagnetic field distribution is performed.

Theoretical Analysis and Design of an Innovative Coil Structure for Transcranial Magnetic Stimulation

Previous research showed that pulsed functional magnetic stimulation can activate brain tissue with optimum intensity and frequency. Conventional stimulation coils are always set as a figure-8 type or Helmholtz. However, the magnetic fields generated by these coils are uniform around the target, and their magnetic stimulation performance still needs improvement. In this paper, a novel type of stimulation coil is proposed to shrink the irritative zone and strengthen the stimulation intensity. Furthermore, the electromagnetic field distribution is calculated and measured. Based on numerical simulations, the proposed coil is compared to traditional coil types. Moreover, the influential factors, such as the diameter and the intersection angle, are also analyzed. It was demonstrated that the proposed coil has a better performance in comparison with the figure-8 coil. Thus, this work suggests a new way to design stimulation coils for transcranial magnetic stimulation.

VISUALIZATION OF MICROWAVE ABSORPTION OF THE GRAPHITE PERIODICAL STRUCTURE WITH THERMOELASTIC OPTICAL MICROSCOPE

This paper shows a non-destructive visualization of the absorption of microwave filed by a graphite periodic structure. The visualization system was a thermo-elastic optical indicator microscope. The article presents the interaction of the electromagnetic field with graphite cylindrical cells of periodicity and shows the distribution of the electromagnetic field over the graphite cells. Depending on the distance between the periodic structure of graphite and the microwave source, the electromagnetic field distribution and absorption rate were different. The visualization was performed using a microwave signal with a frequency of $11~GHz$ and a maximum power of $35~dBm$.