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This paper presents a coupling method of the finite element method and the boundary element method to compute the transmembrane potential (TMP) of an erythrocyte in a low-frequency electric field. We compute an in vitro erythrocyte's TMP induced by external electric fields by this hybrid method. It takes advantage of the homogeneous characteristics from both intracellular region and extracellular region. Moreover, we may use a fine three-dimensional (3-D) mesh around the thin membrane and avoid 3-D meshes in other regions. Numerical results of a spherical cell show that the hybrid method is accurate. The computed threshold of the applied electric field for membrane electric breakdown agrees well with those experimental results. Numerical results can also guide us to locate the maximum induced TMP on the erythrocyte membrane in various electric fields. Some further applications of the hybrid method are also discussed.

Microwave-assisted chemical reactions have been widely used, but the overheating effect limits further applications. The aim of this paper is to investigate the coupling degree of the electromagnetic field and thermal field in microwave-heating chemical reactions whose polarization changes as the reactions proceed. First, the entropy-balance equation of microwave-heating polar-molecule reactions is obtained. Then, the coupling degree of the electromagnetic field and the thermal field in microwave-heating polar-molecule reactions is derived, according to the entropy-balance equation. Finally, the effects of reaction processes on the degree of coupling are discussed. When the time scale of the component-concentration variation is much greater than the wave period during the chemical processes, the degree of coupling is sufficiently small, and the electric and thermal fields are considered as weakly coupled. On the other hand, the degree of coupling may change during the reactions. If the absolute value of the coupling degree becomes larger, due to the change in component concentration, this will lead to a transition from weak coupling to strong coupling. [ABSTRACT FROM AUTHOR]

This article reports experimental observation of rotating plasma discharges in a coaxial structure at a frequency of 2.45 GHz and under atmospheric pressure. In contrast to other cases, the discharge in our case spins without external static magnetic field or moving electrodes. Its formation and impact factors are experimentally explored. Results show that the rotating discharge, especially the peculiarities of its rotation velocity, is attributed to the combined action of gas flow and electromagnetic field intensity between the conductors. Raising the electromagnetic field intensity or reducing the gas flow rate in appropriate ranges can result in a notable increase of the rotation speed. Experiments also demonstrate that the rotation properties are independent of the coaxial dimensions. This article is supposed to provide a new thinking and guidelines for inducing rotating discharge in a coaxial structure without electrodes moving or external magnetic field. [ABSTRACT FROM AUTHOR]

Microwave selective/localized heating has been widely used in special areas, e.g., medical treatment and food processing, but the control of selective/localized heating in restricted space, e.g., microwave ovens, is difficult to accomplish. In this article, a Giuseppe Peano fractal phased-array antenna is designed, and the phase of each radiator is derived to achieve the arbitrary spatial division of the electromagnetic field in a cavity based on the superposition principle of waves. Then, a multiphysics model of microwave heating is established by coupling the electromagnetic field and heat transfer to simulate the directional control of microwave heating in a cavity. An experimental system is built, and the heating results are measured using an infrared thermal imager to verify the temperature distribution in different spatial regions. Finally, the feasibility of the model for different heating targets is discussed. [ABSTRACT FROM AUTHOR]

A 5.8 GHz Fabry–Perot resonator antenna is proposed to improve the performance of the spin rectification effect and inverse spin Hall effect in the far field region. A planar inverse F-shaped antenna and a metamaterial superstrate are used to increase the magnitude of the electromagnetic field. The microwave electric field is enhanced by ∼10-fold, while the magnetic field is enhanced by ∼80-fold. Experimental results prove that the dc signal from the spin rectification effect and inverse spin Hall effect is significantly improved. This letter paves the way for the use of spintronic devices in wireless excitation applications. [ABSTRACT FROM AUTHOR]

• Time reversal is applied to achieve directional microwave heating. • A method is proposed to quantify the difference of electromagnetic field distribution before and after time reversal. • A method for calculating the amount of information during time reversal based on information theory is presented. • A directional microwave heating model based on time reversal is established and simulated. Microwave heating has found extensive applications across diverse industries. However, achieving directional heating remains a significant challenge due to the complexities involved in controlling the electromagnetic field distribution. To address this issue, a novel directional heating method based on time reversal is proposed in this paper. A small signal source is placed at the heated medium to radiate electromagnetic waves. The information received by each receiving unit undergoes specialized processing before being transmitted back to the cavity. Consequently, the time reversal electromagnetic field of each receiving unit gathers at the heating material to achieve directional heating. Moreover, methods are being proposed to calculate the amount of information during time reversal using information theory. These approaches also aim to quantify the disparity in electromagnetic field distribution before and after the time reversal process. A comprehensive multi-physics model of microwave heating is established to simulate the directional heating process based on time reversal. An experimental system is also constructed to validate the proposed model, where the heating results are measured by an infrared thermal imager and a thermocouple. Finally, the effects of frequency, power and phase on the performance of directional microwave heating are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, the electromagnetic environment (EME) characteristics on Wangjiang campus of Sichuan University, a typical densely populated urban area, are measured and analyzed. According to the people's daily routine, the EME measurements are performed during daytime, nighttime, weekday, and weekend, respectively. By measuring the electric field (E‐field) values along the main roads on the campus, the maps of E‐field spatial distribution are obtained. Results indicate that the EME on the campus is relatively stable. The probability density functions of three orthogonal components of E‐field are all lognormal distribution and very similar to each other due to depolarization phenomenon and polarization rotation of multipath propagation. Moreover, the total E‐field is also lognormal distribution because of the high linear correlation between the components. In addition, E‐field were also measured over time on three different sites, playground, laboratory, and student dormitory, in order to get time‐varying characteristics of the EME. Results suggest how the people's activities influence on EME. All measurements on Wangjiang campus show that the maximum E‐field value is far below the regulatory exposure limits proposed by the International Commission on Non‐Ionizing Radiation Protection. Key Points: Electromagnetic environment characteristics on Wangjiang campus of Sichuan UniversityMeasurement of E‐field spatial and temporal distributionThree orthogonal components of E‐field obey lognormal distribution [ABSTRACT FROM AUTHOR]

Available microwave notch-type damage detection sensors are typically based on monitoring frequency shift or magnitude changes. However, frequency shift testing needs sweep-frequency data that make scanning detection becomes difficult and time-consuming. This work presents a microwave near-field nondestructive testing sensor for detecting sub-millimeter notch-type damage detection in metallic surfaces. The sensor is loaded with an interdigital electrode element in an open-ended coaxial. It is simple to fabricate and inexpensive, as it is etched on the RC4003 patch by using printed circuit board technology. The detection is achieved by monitoring changes in reflection amplitude, which is caused by perturbing the electromagnetic field around the interdigital structure. The proposed sensor was tested on a metallic plate with different defects, and the experimental results indicated that the interdigital electrode probe can determine the orientation, localization and dimension of surface notch-type damage. [ABSTRACT FROM AUTHOR]

The resonant cavity antenna (RCA) is a class of widely used high gain antennas, but usually suffers from narrow impedance bandwidth owing to its strong resonant property, as well as relatively low aperture efficiency because of its non-uniform electromagnetic (EM) field distribution on the aperture. This article explores enhancing the RCA's impedance bandwidth and aperture efficiency by designing a non-uniform metamaterial inspired superstrate, on which the metal patches vary their sizes with respect to their distances to the superstrate's center. After optimized by the Genetic Algorithm, the proposed RCA is designed, fabricated and tested. Measured results agree well with simulated ones and show that in comparison with a RCA with a uniform metamaterial inspired superstrate, this work significantly improves the | S11| < −10 dB impedance bandwidth from 2.1% to 6.1%, the gain at the working frequency 10 GHz from 19.07 dBi to 20.55 dBi, and correspondingly the aperture efficiency from 50.5% to 71%. A further analysis estimates that due to the non-uniform metamaterial inspired superstrate, a more homogeneous distribution for both the amplitude and phase of the EM field is observed on the superstrate's aperture. [ABSTRACT FROM AUTHOR]

The artificial neural network (ANN) modeling of electromagnetic interference from a nonlinear device connected with transmission lines exposed to electromagnetic field to the linear device inside a metal enclosure is investigated in this paper. A rectangular loop antenna operating at 2.5 GHz is used to excite electromagnetic field inside an enclosure with dimension 99 × 49 × 44 cm3. Another wideband loop antenna welded with a HSMS-282C Schottky diode pair is used as the nonlinear device connected with the transmission line in order to enhance the coupling and radiating effects inside the enclosure. The linear devices are three monopole probes connected with spectrum analyzer to measure the output power. Experimental results show that the output power from probes near the wideband loop welding with a pair of diodes contains not only fundamental but harmonic components, which are caused by the nonlinear response of diodes excited by induced current. A three-layer ANN model is proposed to predict this nonlinear electromagnetic interference inside the metal enclosure. Results show that the trained BL-MLP model using 576 measured data can predict the response of probes (linear device) interfered by the loop antenna welding with diodes (nonlinear device) inside the cavity well. [ABSTRACT FROM PUBLISHER]

In some cases such as heating objects by microwave power, variation of the temperature in objects changes their dielectric permittivity and then leads to variation of the electromagnetic (EM) field. The commonly adopted method of simulation for the heating procedure is to repeatedly execute the full-wave simulation for each small time intervals, which results in a heavy computation burden. A fast algorithm for simulating 2-D sceneries is proposed for the first time. It starts with a full-wave simulation to get an initial EM field, and then corrects the EM field in an efficient way rather than repeating the full-wave simulation when the object's permittivity has slightly changed. A few sample numerical results are presented and analyzed, which verifies the accuracy, robustness, and effectiveness of the proposed fast algorithm. [ABSTRACT FROM PUBLISHER]

A novel cosimulation algorithm that combines physical-model-based multiphysics simulation with equivalent-model-based circuit simulation is proposed. In the algorithm, multiphysics simulation couples multiple physical equations (e.g., the electromagnetic, semiconductor transport, thermodynamics equations, etc.) to be solved numerically by an iterative approach. The multiphysics simulation is for modeling the electrothermal behavior of semiconductor devices, and then, it is incorporated into the circuit simulation to extend the simulation from semiconductor devices to circuits. Employing the proposed algorithm, sample numerical results for the temperature effect on circuits comprising commercial p-type–intrinsic–n-type diodes with a model number of mot_bal99lt1 are obtained and compared to measurement data. The comparison shows a good agreement between these two sets of data, which validates the feasibility and accuracy of the proposed algorithm. Moreover, the proposed algorithm can provide a useful physical mechanism for understanding temperature effect on semiconductor devices and circuits. [ABSTRACT FROM PUBLISHER]

Multiphysics modeling is an essential tool to understand the heating characteristics of microwave processing food products. However, when the heated sample is moving and deforming during the heating process (e.g. the long-term microwave drying process), the huge mesh distortions caused by the sample's motion and deformation will make the simulation impossible. To solve this problem, a hybrid double-layer Arbitrary-Lagrange-Eulerian (ALE)/implicit algorithm is proposed in this paper, where the sample's motion and deformation is tracked by a double-layer ALE framework and convert to time-varying implicit variables. By doing so, the influence of the sample motion and deformation on the electromagnetic field distribution will be characterized by the evolution of time-varying implicit variables, rather than by explicit modeling, which reduces the mesh distortion and makes the calculation possible. A two-dimensional and a three-dimensional model of microwave cavities containing a rotating and deforming food are given to describe the algorithm in detail. Experiments for the three-dimensional model are also conducted to validate the proposed method. Results show that the shrinkage of the food may have a negative impact on the heating performance (especially energy efficiency) and corresponding remedies need to be performed for long-term microwave heating processes. • Double-layer ALE framework is used to track the deformation and movement of foods. • Mesh distortion caused by the food deformation and motion is weakened by the proposed hybrid algorithm. • This algorithm is applicable to the cases with the moving food expanding or shrinking. • Heating dynamics of microwave heating processes considering heat and mass transfer, deformation, and motion is analyzed. [ABSTRACT FROM AUTHOR]

Making samples moving during microwave heating is popular way to improve the heating uniformity. However, the common methods, e.g. using turntable and conveyor belt, can only make samples move in one plane, resulting in limited effect on improving the heating uniformity. In order to improve the uniformity of microwave heating in both horizontal and vertical directions, a rotary lifting turntable is used to drive the sample to rotate and lift during heating in this work. To observe the improvement of heating uniformity caused by the rotary lifting motion, an algorithm based on level set methods and implicit function are used to model the process. The electromagnetic field distribution during the heating process obtained by the model is verified by the discrete locations. The transient-temperature of three points and the spatial temperature profile obtained by the model are verified by the experiments. With this model, the heating effect of samples in rotary lifting motion is compared to that of samples only in rotary or lifting motion. The results show that the heating effect of the samples in rotary lifting motion is better than that of most of the samples in static state and single motion mode. In addition, influences of rotating speed, lifting speed, sample properties, and diameter of spiral motion on the heating effect is also analyzed. Since the proposed motion mode is aimed to change the horizontal and vertical position of the sample in the electromagnetic field to make the sample absorb microwave uniformly in all directions, it can be applied to all kinds of microwave cavities regardless of geometric shapes. • A multiphysics model for heating processes with a solid sample in rotary lifting motion is developed. • Implicit function and level set methods are used to update the permittivity of the moving region. • Heating efficiency and uniformity are improved by the rotary lifting motion. • Influence of rotating and lifting speed, sample property, and diameter of spiral motion on the heating effect is analyzed. [ABSTRACT FROM AUTHOR]

Moving objects are widely applied in microwave heating process for improving heating uniformity. In order to improve the heating effect, various moving objects with complex shapes will be used in microwave heating. However, for objects with irregular shapes, it is difficult to model the object movement due to the difficulty of characterizing the object's boundaries. In this paper, by using Arbitrary Lagrange Eulerian (ALE) method to track the object movement, the position of the object is expressed by a time-varying implicit function. The impact of the moving object on the electromagnetic field distribution is therefore represented by the change of the implicit parameter. Meanwhile, after the heat source is transformed back to the initial position by a coordinate transformation method, the calculation of the heating process of the moving object can be realized in a fixed mesh structure, thus re-meshing is avoided. A 2-D model and a 3-D model with rotating objects in irregular shapes are used to illustrate the proposed method. Experiments are conducted to testify the validity of the proposed method. Good agreements have been obtained. Moreover, the results show that, for dealing with the cases with moving objects in complex shapes, this method is much more accurate and efficient than the ALE-remeshing method. • Instead of using mathematical definition, ALE method was used to update the implicit function of the moving object. • Boundaries of arbitrary shape moving objects during microwave heating can be simply traced by the proposed ALE scheme. • Remeshing was avoided due to the use of time-varying implicit function to express the motion of the object. • Compared with ALE-remeshing method, the proposed method was more efficient and accurate. [ABSTRACT FROM AUTHOR]