Journal of Microwave Power and Electromagnetic Energy最新文献

{"title":"Editor’s message: cooling evolution for validating microwave heating models","authors":"J. Aguilar-Garib","doi":"10.1080/08327823.2021.1959236","DOIUrl":"https://doi.org/10.1080/08327823.2021.1959236","url":null,"abstract":"Heating with the purpose of conducting a process is one of the most important non-communication applications of microwaves. Given the importance of the temperature as a variable for designing different systems, such as curing, sintering, drying, or food cooking, there is a great deal of interest in measurement techniques, as well as modeling and simulation. Since it is very important to know the thermal profile and its evolution while heating of materials, there are great efforts in the designing of instruments and devices for temperature measurement, and the development of mathematical models for calculating the heat distribution and temperature profiles. Both, temperature measurement and validation of the models are in the case of microwave heating very difficult. In addition to conduction, convection, and radiation (infrared) mechanisms for heat transfer, in the case of microwaves the generated heat within the sample depends on the electric field profile that depends on the permittivity of the sample, that depends on the temperature, which in turn depends on the electric field and the permittivity. It is impossible to have a homogeneous material, slight differences in composition affect everything else. In most cases, the only available information is the external temperature. This is a common problem in engineering known as the boundary value problem. Heat transfer is described with differential equations, solved either analytical or numerical, to describe the temperature inside the sample. It is possible to insert thermocouples, in the case of conventional heating, to follow thermal evolution, but that is more complicated in the case of microwaves because even when they could sense the temperature correctly, they affect the electric field. Validity of a model depends on the accuracy of the set of equations for describing the involved phenomena often referred to as “Multiphysics”, and the right thermal and electromagnetic characterization of the system, as well as the knowledge of the functional relation of the properties with different variables. However, the thermal profile calculated with such a model requires some sort of validation, and it happens that the inner of the sample cannot be seen. Physical evidence of the achieved temperatures can be found after heating, such as cured zones, phase transformation, or confirmation of molten zones, but in the case of microwaves that information does not allow to build a thermal profile because they could be either thermal sources or thermal absorbers, therefore the possibility of validating a thermal profile is limited. The validation of microwave heating models could be conducted by focusing on the cooling part after the microwaves are shut off so that we have only conduction within the sample with known boundary conditions. We have access to the external temperature, then we can follow that evolution. The idea consists of heating a sample with microwaves at certain conditions and calculating th","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"14 1","pages":"173 - 174"},"PeriodicalIF":1.5,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85709827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microwave upgradation of Yunnan lignite: dielectric properties, drying pattern and kinetics","authors":"Lei Guo, Chenhui Liu, C. Srinivasakannan, Gao Jiyun","doi":"10.1080/08327823.2021.1952834","DOIUrl":"https://doi.org/10.1080/08327823.2021.1952834","url":null,"abstract":"Abstract The work attempts to investigate the dielectric properties and microwave drying characteristics of Yunnan lignite, so as to upgrade it. The effect of drying temperature, moisture content and microwave heating frequency on dielectric properties was measured using resonant cavity method. Results indicate that both the values of ε′ and ε″ presented two stage at the investigated temperatures. Bulk water was found to be the main factor contributing to an increase in the ε′ and ε″. Microwave drying kinetics of lignite were carried out. The Page model was the best model reflecting the drying kinetics, and the effective diffusion coefficient and active energy at different drying stages were obtained. In addition, the microwave drying mechanism has been proposed based on the study of dielectric and drying properties of lignite. The SEM images indicated that microchannels were formed within the lignite particle by the microwave pumping effect. FT-IR spectra showed that the oxygen-containing functional groups and hydrogen bonds between them were break by microwave drying. Based on the achieved results, the microwave treatment at 150 °C is helpful to upgrade the lignite.","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"15 1","pages":"248 - 269"},"PeriodicalIF":1.5,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84673608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The use of microwaves in the process of obtaining nanopowders","authors":"L. Bandici, G. Banu, A. Ficai, D. Ficai","doi":"10.1080/08327823.2021.1916681","DOIUrl":"https://doi.org/10.1080/08327823.2021.1916681","url":null,"abstract":"Abstract We present a new approach to the study of microwave efficiency (MW) and microwave susceptors in the process of obtaining high quality nanopowders. Susceptors accelerate the processing of various poorly absorbent materials in the microwave field, reduce processing time and energy consumption. We calculated the electric field by a three-dimensional modelling of a microwave applicator designed to obtain nanopowders. The main objective is to optimize the technology of nanopowder production, by using raw materials and catalysts to ensure low processing temperatures. The performance of nanopowders was evaluated by physical-chemical, morphological, phase methods.","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"98 1","pages":"107 - 127"},"PeriodicalIF":1.5,"publicationDate":"2021-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90803177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of microwave radiation on the magnetic properties of ludwigite and iron-boron separation","authors":"Wei-jun Huang, Yajing Liu","doi":"10.1080/08327823.2021.1916682","DOIUrl":"https://doi.org/10.1080/08327823.2021.1916682","url":null,"abstract":"Abstract To effectively separate and recover the valuable elements iron and boron from ludwigite, this study investigated the magnetic properties and the magnetic separation efficiency. And the reactivity of boron component in the B-bearing tailing was studied. The results indicated that the saturation magnetization of ore samples was increased with the increase of microwave power and heating time. Under condition of 40 s with 4 kW, the saturation magnetization of ore samples increased from 12.73 emu/g for the raw ore to 24.70 emu/g for the treated ore, an increased of 94.03%. After magnetic separation, the grade and recovery rate of iron in the iron concentrate and the boron grade in the tailing for the treated sample with 4 kW for 40 s were increased by 19.74%, 31.46% and 86.46% in comparison with those of the untreated ore. The sample was heated to 600 °C at 4 kW and held for 20 min, the reactivity of boron component in the B-bearing tailing reached 86.68 wt%, which increased by 34.01% compared with that of the raw ore and 4.43% compared with that of the optimal traditional roasting value at 700 °C for 2 h, indicating that the roasting temperature and time were obviously decreased and the reactivity was significantly improved by the microwave radiation.","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"8 1","pages":"93 - 106"},"PeriodicalIF":1.5,"publicationDate":"2021-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78336417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microwave-heated high-silica glass cloth reinforced polyimide-based metamaterial absorber for aircraft deicing","authors":"Zehai Zhang, Jun Zhang, Xiao Liu, Kun Zheng, H. Yi, Jian-sheng Wang","doi":"10.1080/08327823.2021.1916679","DOIUrl":"https://doi.org/10.1080/08327823.2021.1916679","url":null,"abstract":"Abstract This study discusses development of a microwave-heated thin-panel metamaterial absorber (MA) for application in aircraft deicing. The base of the MA was selected to be high-silica glass cloth reinforced polyimide (GCRP), manufactured through the autoclave process. The material’s surfaces were sprayed with metal powder as per the absorber design. In simulation with an optimized parameter set, the MA had a minimum reflectivity of −35 dB at 2.45 GHz. Two rounds of microwave heating experiments were conducted, studying different MA designs. In the first round of experiments, conducted in a stainless-steel mesh chamber, the minimum reflectivity of the first six samples tested, observed at 2.45 GHz, was approximately −5 dB. The accompanying thermal images indicate that the MA is heated periodically, according to the spatial distribution of the electromagnetic field, with an overall heating rate of approximately 0.001 °C/s/W. Clearer thermal images were obtained in the second round of experiments, conducted in a microwave anechoic chamber, where a heating rate of 0.01 °C/s/W was observed near the new MA’s resonant frequency of 2.28 GHz. At this frequency, the MA’s reflectivity was −7.63 dB. These results indicate that the developed MA has potential for application in aircraft deicing.","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"28 1","pages":"140 - 152"},"PeriodicalIF":1.5,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86958167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical modeling of a high power triode-based self-excited oscillator: a path forward more efficient designs and a better frequency stability of low cost high power RF sources","authors":"Victor Guillot","doi":"10.1080/08327823.2021.1916678","DOIUrl":"https://doi.org/10.1080/08327823.2021.1916678","url":null,"abstract":"Abstract Triode-based circuits are still the less expensive and more reliable high power sources for industrial applications between 13.56 and 40.68 Mhz. Among them, self-excited oscillators feature the lower cost but with a frequency stability preventing them to address all ISM frequencies and applications. This article demonstrates the possibility to model numerically self-excited oscillators with power triodes using a class-C practical circuit. Advantages over existing analytical calculations and graphical derivations are shown. A method is proposed to evaluate the frequency stability in presence of internal imperfections and external perturbations. These tools offer the possibility to design and analyze more efficiently this family of oscillators especially for demanding applications regarding frequency stability.","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"2 1","pages":"153 - 171"},"PeriodicalIF":1.5,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82781568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plasma cleaning under low pressures based on the domestic microwave oven","authors":"Li Wu, Zhuang Liu, Wencong Zhang, Xi Feng","doi":"10.1080/08327823.2021.1916680","DOIUrl":"https://doi.org/10.1080/08327823.2021.1916680","url":null,"abstract":"Abstract This article proposed a new solution to do the plasma cleaning under low pressure based on a domestic microwave oven. A conical bottle was placed in the oven according to the electric field distribution calculated by finite element method and Helmholtz equation. A vacuum pump was employed to make a low pressure environment in the bottle to generate plasma. Experiments demonstrated that discharges in the domestic microwave oven under low pressures from 100 Pa to 300 Pa can be easily triggered and maintained when the working gases were argon and air. The lower the pressure was, the easier to trigger and generate plasma, and the more uniform the plasma inside the conical bottle was. Experiments also found that this low-pressure Ar plasma generated in the domestic microwave oven can efficiently clean up the oils on the metallic sheets or glass substrates without damaging them.","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"8 1","pages":"128 - 139"},"PeriodicalIF":1.5,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89493264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Editor’s message: Substance of non-communication applications in JMPEE","authors":"J. Aguilar-Garib","doi":"10.1080/08327823.2021.1924023","DOIUrl":"https://doi.org/10.1080/08327823.2021.1924023","url":null,"abstract":"","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"44 1","pages":"91 - 92"},"PeriodicalIF":1.5,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86959965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of heating performance between inverter and cycled microwave heating of foods using a coupled multiphysics-kinetic model","authors":"Ran Yang, Qianyi Chen, Jiajia Chen","doi":"10.1080/08327823.2021.1877244","DOIUrl":"https://doi.org/10.1080/08327823.2021.1877244","url":null,"abstract":"Abstract Non-uniform heating has been a challenging problem in microwave heating due to ‘standing wave pattern’ and ‘thermal runaway’ problems. Cycled microwave heating was used to improve microwave heating uniformity of frozen products, while a relatively new approach of inverter heating was claimed to help preserve food quality during thawing/heating. In this study, finite-element-method-based coupled multiphysics-kinetic models were developed, validated, and used to investigate these controversial results by comparing the heating performances of average temperature, heating non-uniformity, and nutritional value change between the inverter and cycled microwave heating of foods. The effect of food sizes/shapes and material properties (dielectric loss) was evaluated. Results showed that there was little difference in average temperature, heating uniformity, and Vitamin C content between cycled and inverter heating for different food products. A relatively more uniform heating and lower nutritional value degradation were observed for small size low loss material; however, the improvement was not significant enough to claim the benefit of inverter heating.","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"18 1","pages":"45 - 65"},"PeriodicalIF":1.5,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88436402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Editor’s message: Microwave imaging advances","authors":"J. Aguilar-Garib","doi":"10.1080/08327823.2021.1880858","DOIUrl":"https://doi.org/10.1080/08327823.2021.1880858","url":null,"abstract":"Since visual representations are more efficient in transmitting ideas, usually, plots are preferred over tables, schemes as a complement of text descriptions and pictures as evidence in a sense of “An image is worth a thousand words.” Picturing the visible light world seems to be the easiest of all, but it depends on the details that we wish to capture; the resolution is limited by the light wavelength and our eyes are also part of the optical system. Interaction wave-matter can lead to wave transmission, absorption, and reflection, as energetic beams hitting a sample can produce secondary electrons, backscattered electrons, x-rays, or heat, which can be detected for constructing with electronic devices an image that we can see. An important application of high energy radiation is for industrial testing and analysis, such as welding cords inspection and search of cracks inside materials. The attractiveness of these techniques, considered as non-destructive in that field, is that they make it possible to see inside the samples. In the same manner, not invasive medical diagnosis is of the same interest for clinical applications, and even more, the patients, who prefer to avoid surgeries. However, ionizing radiation is hazardous for us and there is no way that it can be considered as not invasive. Certainly, concerns in medicine, regarding the exposition of patients to these radiation forms either for diagnosis or treatment purposes has increased significative since R€ ontgen discovered the x-rays to visualize, with radiography, the inside of the body, so that nowadays, the development of techniques for reducing the risks are in progress. Decreasing the doses with more sensitive devices and changing to lower energy radiation sources, such as in soft x-rays, microwaves, and RF, are among the possibilities. Insistence on claims usually presented on the internet about microwave hazards for healthy, forces to cast comments about that in terms of safety. For instance, the report entitled “Review of Published Literature between 2008 and 2018 of Relevance to Radiofrequency Radiation and Cancer” published by the FDA U.S. Food & Drug, Center for Devices and Radiological Health, in February 2020, indicates that there is insufficient evidence to support a causal association between RFR exposure and tumorigenesis. Moreover, despite the complaints against mobile phones (RFR), according to the World Bank, there were in 2019, 8196 million mobile phone subscriptions worldwide, about 1 per habitant, so that there is evidence of a certain population level of confidence. Microwave imaging is not new; more than 30 years of research have produced advances in impedance imaging with some resolution problems, antennas with good stability of the directionality, confirmation of differences between healthy and cancerous breast tissues, comparisons with images obtained by other techniques; thermography, and tomography. However, it seems that the most noticeable application is ","PeriodicalId":16556,"journal":{"name":"Journal of Microwave Power and Electromagnetic Energy","volume":"9 1","pages":"1 - 2"},"PeriodicalIF":1.5,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74269675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}