ANALYSIS OF HIGH-FREQUENCY C-CORE MAGNETIC FLUX LEAKAGES FOR BONE TUMOR WITH INDUCTION HEATING BY USING MULTI-COIL

High-frequency magnetic field has been developed pervasively. The induction of heat from the magnetic field can help to treat tumor tissue to a certain extent. Normally, treatment by the low-frequency magnetic field needed to be combined with magnetic substances. To assist in the induction of magnetic fields and reduce flux leakage. However, there are studies that have found that high frequencies can cause heat to tumor tissue. In this paper present, a new magnetic application will focus on the analysis of the high-frequency magnetic nickel core with multi-coil. In order to focus the heat energy using a high-frequency magnetic field into the tumor tissue. The magnetic coil was excited by 915 MHz signal and the combination of tissues used are muscle, bone, and tumor. The magnetic power on the heating predicted by the analytical model, the power loss density (2.98e-6 w/m3) was analyzed using the CST microwave studio.

SINTERING OF MLCC’S BARIUM TITANATE WITH MICROWAVES

A comparison of microwave and conventional, in an electric resistance furnace, sintered layers of dielectric base barium titanate (BaTiO3) of the kind employed for multilayer ceramic capacitors (MLCC) was performed. Two kinds of samples were used for each processing method; the layers alone without electrodes, and the green MLCC with the layers and electrodes interdigitated. Samples were exposed to microwaves for 20 minutes and heated up to 1050°C and 1150°C for sintering in a crucible with graphite that acted as reduction agent and microwave susceptor. Conventional sintering was performed in the same arrangement but lasted 120 minutes since it was found that 20 minutes was not enough time to achieve sintering. Heating rate in both cases was 10 °C/min. It was observed that the layers without the electrodes achieve about the same densification for both processes, while in the case of the green MLCC’s the results were variable, ranging from sample that became dust, to cracked samples and some well sintered ones. At least in the microwave case, it is possible that the variability of the results is due to the importance of the location of the sample in the cavity that in turn affects the electric field pattern, especially because the presence of the electrodes that can cause overheating around them.

SOLID-STATE MICROWAVE PROCESSOR FOR FOOD TREATMENT

Uneven heating and hot spots, irregular matching conditions and deterioration of organoleptic qualities are typical drawbacks of magnetron-based food processing with microwave radiation. The proposed “Kopernicook” modular architecture, based on multiple solid-state generators governed by a distributed software platform, allows highly accurate parametric control, full customization of radiation patterns and dynamic self-regulating workflows. The first results, validated with industrial applications, show great flexibility of operation, optimal energy consumption and different ideas for future developments in terms of radiation patterns and feedback-triggered algorithms aimed at maximally efficient processes.

Automatic Measurement of Magnetron Rieke Diagrams

A Rieke diagram [1] is a magnetron characteristic that visualizes the dependence of the generated frequency fg and the net delivered power PL on the load reflection coefficient GR. GR is defined in a specific magnetron-to-waveguide coupling structure called the standard or reference launcher (Fig. 1). The diagram is plotted as a family of isolines of constant fg and of constant PL in the polar diagram of GR. Rieke diagrams are essential in the design of applications without isolators, such as domestic or professional microwave ovens. Constructing Rieke diagrams is tedious, time-consuming and equipment-demanding [2], [3], preventing systematic studies of their dependence on operating conditions, such as anode voltage and its ripple, filament current, mounting repeatability, etc. We have devised a procedure, centering around a high-power automatic impedance matching device (autotuner), which enables fully automatic measurement and plotting of the stated dependences. A block diagram of the setup is shown in Fig. 1. The autotuner, when terminated in a match (waterload), can accomplish a task inverse to impedance matching: realizing any desired reflection coefficient GR. The measurement consists of stepping through a grid of n suitably chosen reflection coefficients GR = xR + jyR, covering a desired area of the polar diagram. Each GR is measured accurately by the autotuner, along with the corresponding fg and PL. Thus, raw data for constructing a Rieke diagram are obtained, the data consisting of a collection of n points {GR, fg, PL}i, i = 1…n, with GR, in general, irregularly scattered in the complex plane. A dedicated MATLAB routine then reads the data, sorts them out to create tabulated functions fg = f(xR, yR), PL = f(xR, yR), approximates these by a 2D spline, and uses the splines to plot smoothed isocontours for chosen constant values of fg and PL, completing thus the desired Rieke diagram construction. We will present details of this procedure as well as real-life examples. Fig. 1. Rieke diagram measurement setup. References Meredith, R. J., Engineers' Handbook of Industrial Microwave Heating, London: The IEE, 1998, 250–270. Takahashi, H., I. Namba, K. Akiyama, J. Microwave Power, 1979, 14, 261–267.Yixue, W., Z. Zhaotang, Proc. ICMMT'98, 1998, 795–798.

A HIGH-POWER SOURCE OF OPTICAL RADIATION WITH MICROWAVE EXCITATION

For more than 50 years, interest to the microwave heating technology has not weakened. In addition to the traditional areas of its application, which described in detail in [1], recently there has been an expansion of technological possibilities for the use of microwave energy associated with the impact of electromagnetic waves of the microwave range on various materials (sintering of metal and ceramic powders) and media, including plasma [2]. One such new direction is the creation of high-power and environmentally friendly sources of optical radiation on the basis of an electrodeless sulfur lamp with microwave excitation [2, 3]. The purpose of this paper is to the further development of the theory and practice of microwave excitation by the electrodeless sulfur lamps, improvement the energy efficiency during energy conversion into the optical radiation and widening the application of new light sources in real practice. The results of the computer modeling of conversion process of the microwave energy into optical radiation energy are presented. The simulation results are compared with experimental data. It is shown that additional use of the solar panels for the reverse conversion of the optical radiation into DC energy with follow-up its using in the circuits of secondary power supply allows improving the energy efficiency of the light source. References Microwave Power Engineering. Edited by E.C. Okress. V. 1, 2. Academic Press, New York & London. 1968.A.N. Didenko, SVCh-energetika. Teoriya i praktika. – Moscow: Nauka. 2003.- 445 s.G. Churyumov, T. Frolova, “Microwave Energy and Light Energy Transformation: Methods, Schemes and Designs. Microwave Energy and Light Energy Transformation: Methods, Schemes and Designs” // In book “Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing.” Edited by Kok Yeow You, IntechOpen, 2018. pp. 75-91.

Microwave-assisted preparation of ZnS and ZnSe nanocrystals with different morphologies for photodegradation process of organic dyes

Zinc sulphide (ZnS) and zinc selenide (ZnSe) and manganese-doped and un-doped with different morphologies from 1D do 3D microflowers were successfully fabricated in only a few minutes by solvothermal reactions under microwave irradiation. In order to compare the effect of microwave heating on the properties of obtained nanocrystals, additionally the synthesis under conventional heating was conducted additionally in similar conditions. The obtained nanocrystals were systematically characterized in terms of structural and optical properties using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-Vis spectroscopy (DR UV-Vis), Fourier-transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area analysis. The photocatalytic activity of ZnSe, ZnS, ZnS:Mn and ZnSe:Mn nanocrystals with different morphologies was evaluated by the degradation of methyl orange (MO) and Rhodamine 6G (R6G), respectively. The results show that Mn doped NCs samples had higher coefficient of degradation of organic dyes under ultraviolet irradiation (UV).

A new concept to improve microwave heating uniformity through data-driven process modelling

For a long time, the heating pattern of the workpiece within a multimode microwave oven was considered to be highly sophisticated. As a consequence, the uneven microwave heating problem can only be partly alleviated by a random movement between the electromagnetic field and the workpiece. In this paper, we reported that the heating pattern has a specific correspondence with microwave system settings. The influence factor of the heating pattern and the corresponding mechanism were systematically studied by both theoretical analysis and experimental investigations. On this basis, a data-driven process model was established to learn the material’s dynamic temperature behaviors under different microwave system settings, and a new concept to improve the microwave heating uniformity by temperature monitoring and active compensation was proposed. The effectiveness of the method was demonstrated by a polymer composite microwave processing case study.

FEATURES OF UTILITARIAN STONEWARE FIRED WITH MICROWAVE RADIATION

The energy dependence on fossil resources and the increasing competitiveness of the stoneware industry, which is a relevant natural gas consumer, leads to new and more environmentally friendly firing methods. Microwave radiation is herein presented as an alternative heating technology for stoneware firing. The samples were fired in a multimode furnace with 6 magnetrons in its core, each one operating at a nominal power of 900 W and frequency of 2.45 GHz. A pyrometer and a thermocouple were installed in the microwave furnace for temperature measuring, control and monitoring. Pyrometer was calibrated in an electric furnace for accurate temperature measurements. During calibration, the thermocouple used in the microwave furnace was installed in the electric furnace, giving a temperature difference from the control (electric furnace) of 2 to 5 ºC, from room temperature up to 1450 ºC. To help the stoneware firing, a silicon carbide (SiC) plate was used as microwave susceptor, also working as a support base for the stoneware samples (mugs). The microstructure of the microwave fired stoneware shows features similar to those of conventionally fired samples (gas and electric heating), with the microwave requiring lower firing temperature to reach an equal structure. X-Ray diffraction and scanning electron micrograph show the relevant transformations taking place for lower temperatures when using microwave heating.

ON THE POSSIBILITIES OF PERMITTIVITY CALCULATION IN A CERTAIN BANDWIDTH FROM SINGLE FREQUENCY RESULTS

The permittivity of a material can be obtained from resonant measurements in an accurate way [1] at a single frequency (where the resonance occurs). In figure (1) results for the Debye Model at 298K temperature can be seen in the 10MHz-50GHz frequency band for distilled water. In this work we explore the possibilities of obtaining the permittivity of materials from resonant measurements in a certain frequency bandwidth around the resonance frequency. With this purpose a Debye model jointly with a certain conductivity useful for polar liquids [1], are studied to evaluate this possibility jointly with inverse techniques.