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This study investigates the counterintuitive behaviors of a microwave‐induced atmospheric pressure plasma jet (APPJ) under the influence of an external electrostatic field applied by one or a pair of parallel electrode plates subjected to DC voltages. The findings demonstrate that the plasma jet consistently deflects toward the electrode plate with an electrostatic potential, irrespective of the direction of the applied field. The deflection becomes more pronounced with increasing voltage on the electrode plate until the ionic wind generated by the high voltage significantly affects the jet's behavior. Remarkably, a negative voltage induces a greater deflection compared to a positive voltage. To further investigate this discovery, the dielectric properties and the non‐neutral characteristics of the APPJ are analyzed, and the simulations of the electric field distribution reveal a non‐uniform distribution, which plays a crucial role in understanding the mechanism behind the observed behaviors of the plasma jet. This study provides a comprehensive understanding of the underlying mechanism driving the observed phenomena and sheds light on the collective behavior of plasma jets under non‐uniform electric fields. The findings of this study offer valuable guidelines for investigating and controlling the behavior of APPJs. [ABSTRACT FROM AUTHOR]

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]

A dual-band sensor based on a planar rectangular cavity loaded with pairs of improved planar resonator is used to measure the permittivity difference of liquids with a small volume ($2.5~\mu \text{l}$). The planar cavity is connected by two microstrip transmission lines, constituting a two-port device with two branches. A pair of interdigital capacitor (IDC)-based split ring resonator (SRR) is coupled to the middle part of each branch. The distance between the IDC–SRRs is large, and their coupling can be neglected. Thus, two resonance frequencies are produced (4.15 and 9.18 GHz). One frequency is generated from the resonance of the two IDC-based SRRs (4.15 GHz), whereas the other results from the coupling of the rectangular cavity and the two IDC-based SRRs (9.18 GHz). Frequency splitting is used to detect changes in the dielectric characteristics of the liquids. If the two branches (IDC-based SRRs) of the proposed sensor are placed on the same liquid, only two resonance frequencies are obtained. When two different liquids are loaded by the sensor, the resonance frequency will be split into four. A planar rectangular cavity is used instead of a splitter configuration to motivate the two IDC–SRRs. This novel design affords a dual-band miniaturized sensor. [ABSTRACT FROM AUTHOR]

The progress of spin rectification effect, which has the potential in powering the nanoscopic devices wirelessly, has been impeded by its low conversion efficiency. To solve this problem, a 5.8 GHz planar inverted F‐shaped antenna, which is designed to harvest radiated microwave power as well as foster a field enhanced area surrounding a permalloy (Py, Ni80Fe20) monolayer, is presented. The electric and magnetic field are enhanced by ~17.5‐fold and ~ 45‐fold, respectively. With the proposed antenna, a photovoltage of 0.85 μV can be detected in the monolayer 1.5 m away from the transmitting antenna, with input power of 30 dBm. This work provides an effective method to enhance the spin rectification effect signal in the far field region and paves the way for spintronic devices to be potentially utilized in practical wireless applications, such as quantum information, photovoltaics, and nanogenerator. [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]

In this paper, a random forest regression (RFR) is proposed to reconstruct the statistical characteristics of electric fields in perforated enclosures. The power balance method and a diffusion equation–based model have been applied to the analysis of such problems; however, they are unable to account for the statistical nonisotropy problem. To solve it, RFR is used to predict the variances of six basic electric fields, the real and imaginary parts of the three rectangular electric field components, in perforated enclosures under external excitation. Using the predicted variances, the probability density function to represent each basic electric field can be generated as they are assumed to obey normal distribution with zero mean value. Then the statistical characteristics of other electric fields can be calculated by an analytical method and Monte Carlo method. Using the proposed method relies on RFR, the overall statistical characteristics of electric fields in perforated enclosures with the electric dimensions less than ten times the wavelength can be accurately reconstructed. Using the predicted statistics, the practical electromagnetic compatibility problem, such as global shielding effectiveness of a perforated enclosure, can be evaluated in seconds. [ABSTRACT FROM AUTHOR]

Conventional microwave oven heating has the problem of poor heating uniformity and low heating efficiency. A novel microwave oven heating model has been proposed for improving heating uniformity by making the electric field in the microwave oven drastically change by changing the geometry of the microwave oven during the heating process. The transformation optics method is used to solve the computational difficulties caused by the continuous change of the mesh during the motion. Finally, the experiment verified the correctness of the simulation. In addition, important factors affecting heating efficiency were discussed. [ABSTRACT FROM AUTHOR]

For the nonlinearly phenomena on the dielectric properties of dimethyl sulfoxide (DMSO)-ethanol mixtures under a low intensity microwave field, we propose a conjecture that there exist some abnormal molecular clusters. To interpret the mechanism of abnormal phenomena and confirm our conjecture about the existence of abnormal molecular clusters, an in-depth investigation about the structure evolutions of (DMSO)m(C2H5OH)n (m = 0-4; n = 0-4; m + n ≤ 4) molecular clusters induced by external electric fields has been given by using density functional theory. The results show that there exist some binary molecular clusters with large cluster radii in mixtures, and some of them are unstable under exposure of electric fields. It implies that the existence of certain abnormal molecular clusters in DMSO-ethanol mixtures results in their abnormality of dielectric properties. [ABSTRACT FROM AUTHOR]

The heating efficiency of sodium chloride solution would be increased with elliptically polarized microwave electric field for that a more frequent motion of water molecules and ions would be generated with multidirectional polarization electric field. [Display omitted] • The heating efficiency of sodium chloride solution with elliptically polarized and linearly polarized microwave electric field was compared. • Rotation autocorrelation function was used to study rotating motion of water molecules with different heating modes. • The hydrogen bonds between water molecules of sodium chloride solution were simulated. Our molecular dynamics simulation results show that the elliptically polarized microwave electric field would increase the heating efficiency of sodium chloride solution. The growth rate of the heating efficiency is positively correlated with the concentration of the sodium chloride solution and intensity of applied electric field. The rotation autocorrelation function results confirm that water molecules would do a more frequent rotational motion with the multidirectional polarization of elliptically polarized microwave electric field. The result of the more frequent rotational motion is consistent with that of the higher microwave energy absorption of energy analysis. The following analysis of hydrogen bond shows that the existence of ionic solutes would break the hydrogen bonds between water molecules and make it easier for water molecules to rotate with the applied electric field. These results indicate that elliptically polarized microwave electric field can indeed improve the heating efficiency of salt solution. [ABSTRACT FROM AUTHOR]

A two-port U-shaped Coplanar Waveguide (U-CPW) used for broadband complex permittivity measurement of high loss solutions is presented. Compared with the one-port measurement device, this two-port U-CPW coupled with artificial neural networks algorithm has the ability of reducing the multiple-solutions. Also, the measured T/R (transmission/reflection) coefficients were used instead of simulated reflection coefficients for training the neural networks that enhanced the accuracy of measurement results. Two real-valued neural networks associated with the U-CPW are used to reconstruct the two parts of the complex permittivity separately from the measured T/R coefficients. First, a large number of measured T/R coefficients of broadband frequency points of ethanol-water mixtures along with their theoretical complex permittivity are used to train two separate neural networks. Second, the trained networks are employed to reconstruct the complex permittivity of other solutions using the measured T/R coefficients. Compared with the results of Cole-Cole equation, the reconstructed results of methanol-water mixtures and ethanol-methanol mixtures at different volume fractions have been obtained with sufficient degree of accuracy in the frequency range 1-3 GHz at 20°C. For predicted values using the developed artificial neural network (ANN) architecture and those obtained from literature, the average relative errors of real and imaginary parts of complex permittivity are 2.27% and 2.12%, respectively. [ABSTRACT FROM AUTHOR]

The temperature of water under the irradiation of two incoherent microwaves rise faster than that of one microwave. [Display omitted] • A microwave Separated Field Reconstructed (SFR) device is established. • Incoherent microwaves heat water at a higher heating rate than one microwave. • The higher heating rate is due to the more discrepant electric field directions. To improve microwave heating efficiency, a combined experimental and simulated investigation of incoherent microwaves heating of water was carried out. The experiment was conducted with Separated Field Reconstructed equipment, which can provide incoherent microwaves generated from two independent sources. Both the experimental and simulated results indicated that, with same total powers, the heating rate of water under the irradiation of two incoherent microwaves was increased than that of one microwave. The enhancement can be understood qualitatively that the more discrepant electric field directions of incoherent microwaves would stimulate more molecular collisions, which would result in a higher heating rate. [ABSTRACT FROM AUTHOR]

The microwave non-thermal effect is still a controversial issue. Here, the influence of weak microwaves on the spatial collision and energy distribution of water molecules is studied by the molecular dynamics simulation. The results show that the polarization of microwaves makes the change of spatial collision and energy distribution. The spatial collision probability of water molecules increases obviously in the direction of electric field and the proportion of high energy molecules decreases while the proportion of intermediate energy molecules increases. This shows the constrains of microwave fields on the water molecules, and these consequences would be helpful to understanding the microwave non-thermal effect and the mechanism of microwaves accelerating chemical reactions. [ABSTRACT FROM AUTHOR]

Environmental crises caused by plastic pollution have spurred the development of novel recovery and upcycling methods. In this study, a microwave magnetic field and magnetic catalyst cracking strategy based on a microwave multi-ridge field compressed reactor was proposed to efficiently convert polyethylene into hydrogen and high-quality carbon nanotubes while minimising energy consumption. A series of catalysts with different iron and cobalt contents was prepared and evaluated for hydrogen production from polyethylene cracking. A high hydrogen yield of 61.6 mmol·g−1 plastic was obtained in the magnetic field position with an energy consumption of only 5 W·h g−1 plastic , whereas the hydrogen yield was 45.7 mmol·g−1 plastic under microwave electric field. Under microwave magnetic field activation, the magnetic catalyst CoFeO x exhibited higher selectivity for H 2 than hydrocarbons in waste plastics. In addition, high hydrogen yields were achieved by varying the ratio of the catalyst feedstock in the electric field and intermediate positions of the reactor. This reactor separates the microwave fields in the reactor and places catalysts with different absorption characteristics at different positions, which can significantly improve the efficiency of microwave energy utilisation. [Display omitted] • Microwave magnetic field assisted pyrolysis of plastics with magnetic catalysts. • Magnetic catalyst CoFeO x was prepared by citric acid combustion method. • Hydrogen production from polyethylene up to 61.6 mmol·g−1 plastic. • Effect of magnetic catalysts on plastic cracking in microwave fields was studied. [ABSTRACT FROM AUTHOR]

• Microwave enhanced catalytic degradation of VOCs. • High electric field distribution exists on the surface of particles. • VOCs molecule activated on the catalyst surface under microwave E-field. • The surface electronic structure was changed under microwave E-field. Microwave can enhance catalytic reaction and is a promising alternative to convention heating. Herein, microwave-enhanced catalytic degradation of benzene was investigated using Co-Mn metal oxides. Numerical calculation was employed to analyze the microwave-enhanced catalytic degradation. The catalysts were synthesized by conventional citrate sol-gel method. Then, the morphologies, elements distribution and chemical structure were characterized. Compared to conventional heating, the catalysts exhibit better activity and lower apparent activation energy under microwave heating, indicating that microwave enhance catalytic degradation of benzene. Mn1Co2 exhibits good catalytic performance under microwave heating. From the finite element simulation, it is found that the E-field distribution on the spherical particle catalyst is non-uniform, and the E-field intensity is about 1.9 × 104 V/m and 4.27 × 104 V/m at the catalyst particles and the contact position. The DFT calculation results show that the electron density of Mn-O bond decreases and the charge density of Co atom increases under E-field, which is conducive to the molecule activation and electron transfer. The density of states results demonstrate the microwave E-field leads to lower electron energy on the surface, resulting in enhanced catalytic reaction. Combined with the results of finite element calculation, the microwave enhancement effect is more pronounced at the catalyst contact point. [Display omitted] [ABSTRACT FROM AUTHOR]

Anomalous dielectric relaxation in complex reactions is difficult to specify, since there is no classic model for the reacting species with anomalous subdiffusion in the presence of an external electric field. In this paper, the anomalous dielectric relaxation of a multispecies system with linear reaction dynamics is studied based on the biased continuous time random walks. Different reaction–subdiffusion equations are derived via the mathematical random subordination time and the deterministic physical time. The mathematical random subordination time is based on the assumption that the jumping probabilities are determined at the end of the waiting times, while the deterministic physical time is based on the assumption that the jumping probabilities are independent of time and evaluated at the start of the waiting times. The force fields are operated by the Riemann–Liouville fractional derivative in the reaction–subdiffusion equations with the deterministic physical time, while the opposite results are found in the reaction–subdiffusion equations with the mathematical random subordination time. The explicit expressions for the anomalous dielectric relaxation of a reversible reaction are further derived according to the two reaction–subdiffusion equations in the presence of space- and time-dependent electric fields. The numerical calculations are carried to validate the reliability of the different expressions for the anomalous dielectric relaxation, and the reaction–subdiffusion equation with the deterministic physical time is proved to be suitable for describing the anomalous dielectric relaxation. • The anomalous dielectric relaxation of multispecies reacting polar molecules is studied. • The biased continuous time random walk theory is applied in the calculation. • Only the deterministic physical time is suitable for describing the dielectric relaxation. [ABSTRACT FROM AUTHOR]

• We found that the solubility of sulfur dioxide decreases under the electric field. • The binding energy of SO 2 and water clusters decreases under electric field. • MD shows that SO 2 is difficult to diffuse under the external electric field. • The results two experiments are consistent with the calculated results. The effect of external electric fields on sulfur dioxide (SO 2) is often neglected, and it is an important source of environmental pollution. We use density functional theory (DFT) to obtain the cluster structures and intermolecular binding energies of SO 2 –(H 2 O) n in the presence of an external electric field and molecular dynamics (MD) to calculate the solutions' properties. The results show that the electric field reduces the binding energy between SO 2 and water, and inhibits the diffusion of SO 2. The positive shift of binding energy and solvation free energy indicates that the solubility of sulfur dioxide decreases under electric field, which is in agreement with our experimental results. The results are helpful to the study of the interaction between sulfur dioxide and water in the strong electric field near the high-voltage line. [ABSTRACT FROM AUTHOR]