Three-dimensional Electromagnetic Field Research Articles

Multi-channel vortex beam based on single layer transmission-type metal metasurface

We design a transmission type flexible metasurface which operates at 0.1 THz. The metasurface consists of a polyimide substrate and a metallic copper film. Using the geometric phase principle, four vortex beams with different channels and different topological charges are generated under the linearly polarized beam incident. Through three-dimensional electromagnetic field simulation and experimental tests, it is proved that the designed metasurface can generate multi-channel vortex beams, where the topological charges of the vortex beam are ± 1 and ± 2. The metasurface has high transmittance in the frequency band of 0.092THz to 0.106THz, 0.202THz to 0.283THz, 0.318THz to 0.345THz, and so on, which can generate multi-channel vortex beams at multiple frequency bands. Metasurfaces designed based on this method can be applied in optical communication.

Grounded source transient electromagnetic 3D forward modeling with the spectral-element method and its application in hydraulic fracturing monitoring

A long wire with large current source transient electromagnetic (TEM) monitoring, with a large detection depth, low cost, safety, and environmental protection, has unique advantages in the testing and identification of unconventional reservoir fluid and the evaluation of stimulated reservoir volume. So, the TEM 3D forward modeling method has become a research hotspot. Although the finite-element method (FEM) is a type of numerical algorithm that has been widely applied in three-dimensional (3D) electromagnetic field forward modeling, the efficiency and accuracy of FEM require further improvement in order to meet the demand of fast 3D inversion. By increasing the order of the basis function and adjusting the principle of mesh discretization, the precision of the mixed-order spectral-element (SEM) result will be increased. The backward Euler scheme is an unconditionally stable technique which can ignore the impact of the scale of the time step. To achieve a better description of the nonlinear electromagnetic (EM) response of the grounded source TEM method and to optimize the efficiency and accuracy/precision of the 3D TEM forward modeling method significantly, we proposed the use of 3D TEM forward modeling based on the mixed-order SEM and the backward Euler scheme, which can obtain more accurate EM results with fewer degrees of freedom. To check its accuracy and efficiency, the 1D and 3D layered models are applied to compare the SEM results with the semi-analytical and FEM solutions. In addition, we analyzed the accuracy and efficiency of the SEM method for different types of order basis functions. Finally, we calculated the long-wire source TEM response for a practical 3D earth model of a shale gas reservoir for fracturing monitoring and tested the feasibility of the TEM method in a hydraulic fracturing monitoring area to further demonstrate the flexibility of the SEM method.

Analysis of C-V2X Antenna Performance on Vehicular Panoramic Glass

This paper presents an analysis of a cellular vehicle-to-everything (C-V2X) quarter-wavelength monopole antenna performance when mounted on full glass roof. Antenna gain measurements performed on a full glass roof exhibited a performance degradation in a linear average gain (LAG) of 8 dB compared to when the same antenna is mounted on a metallic ground plane. In addition, the antenna radiation pattern on the glass roof had deep nulls. Due to a lack of information about the electrical material properties and architecture of the full glass roof sample from the glass supplier for proprietary reasons, a series of gain measurements were performed for the C-V2X monopole when mounted on different glass material samples. The measurement findings suggested the existence of a metal layer in the glass roof sample. Based on this information, the antenna was simulated using a full-wave, three-dimensional electromagnetic field solver on the full glass sample with a low-emissivity (low-E) coating on the edges of the full glass roof. The simulation results showed acceptable agreement with the measurements. A practical solution is suggested to improve the C-V2X antenna performance on the full glass roof. Specific absorption ratio (SAR) analysis is conducted for the passengers in the front and rear seats due to the passenger radiation exposure from the C-V2X monopole antenna mounted on the glass roof. The SAR study showed that the effect of the roof-top C-V2X monopole antenna radiation on the passengers is negligible.

Simulation of power frequency high power electromagnetic coupling heater and analysis of influencing factors

Aiming at the problems existing in current electric energy replacement, such as the random energy fluctuation of the power grid, the energy storage of the power grid and the consumption of new energy, electromagnetic coupling heating technology and methods based on power frequency high power is proposed. According to the theory of electromagnetic induction heating, Maxwell’s equations are used to establish a three-dimensional electromagnetic field simulation model, determining the size of the core and the windings, and completing the structural design of the heater. Based on the simulation model of electromagnetic coupling heater, the back electromotive force of the primary winding, the induced current of the secondary winding, the B–H curve field diagram of the core, and the J-field diagram of the secondary winding are analyzed to explore heating efficiency of the heater and verify the correctness of electromagnetic coupling heating mechanism. The relationship between the coupling gap, the number of heat dissipation rings, and the air gap and heating efficiency of the heater was further explored, and the model structure of the heater was optimized according to the variation rules so that heating efficiency of the heater reached more than 99%. The electromagnetic coupling heater achieves high efficiency, cleanliness and low carbon, and power frequency high power, which is of great significance to the renewal of electric heater in the future.

Autoencoder-extended Conditional Invertible Neural Networks for Unfolding Signal Traces

The reconstruction of cosmic ray-induced air showers from measurements of radio waves constitutes a major challenge. In this work, we focus on recovering the full three-dimensional electromagnetic field from two recorded signal traces of an antenna station covering two horizontal polarization directions. The simulated field is folded by a direction and frequency-dependent characteristic antenna response pattern, resulting in voltage signal traces as a function of time. Both signal traces are contaminated by simulated background noise. We use conditional Invertible Neural Networks (cINNs) to learn posterior distributions, from which the most likely electromagnetic field given a measured signal trace can be inferred. To improve robustness, we extend the method with an autoencoder by reducing the parameter phase space and decoupling the cINN from specific data shapes. Thereby, each signal trace is condensed into a small number of abstract parameters in the latent space on which the cINN operates. The presented method shows promising results and can be transferred to other unfolding problems where the recovery of the pre-measurement state is of interest.

Detection Method for Shrinkage Cavities Inside Spheroidal Graphite Cast Iron Using Vibration Measurement by Electromagnetic Force Excitation

The inspection of shrinkage cavities formed inside spheroidal graphite cast iron during the manufacturing process of spheroidal graphite cast products, including large cast structures and machine parts, is considered to be important for quality assurance of cast products. X-ray and ultrasonic methods are generally used for this inspection. However, the former inspection method takes a long time and considerable equipment costs, the latter method requires the use of water as a contact couplant and to polish the surface of the inspection site of the cast iron. In an actual manufacturing factory, there is a demand for a simple and quick method for inspecting shrinkage cavities inside cast iron. In this research, as a simple and high-speed inspection method to evaluate shrinkage cavities inside cast iron by measuring of the vibration of the electromagnetic force is proposed. Three-dimensional electromagnetic field analysis using the finite element method and displacement analysis was performed to analyze the phenomenon, and the usefulness of this method was confirmed by verification experiments.

Generation of a sub-wavelength sized optical needle with arbitrary longitudinal rotation.

We show that under tight focusing conditions, arbitrarily rotating the longitudinally polarized optical needle in space is possible. Applying the Richards and Wolf vector diffraction methods, the explicit expressions underlying the simultaneous control depth of focus (DoF), intensity suppression of the sidelobes, as well as the orientation of the optical needle can be obtained, and then the strength vectors of the three-dimensional electromagnetic fields can be calculated. Calculations reveal that the sidelobe suppression ratio reaches 5.35% of the principal lobe, the optimal DoF is 5.1λ, and the maximum length is about 18.2λ. In addition, we specify the necessary conditions for rotating the sub-wavelength sized optical needle in the longitudinal field. Such an optical needle with controllable length, purity, and orientation can provide a flexible approach and additional degree of freedom for 3D precise fabrication and some other potential application areas.

Sensitive Detection of Aspartame and Vanillin by Combining Terahertz Fingerprinting With a Metamaterial

In this study, a terahertz (THz) metamaterial based on THz fingerprint is proposed for simultaneous measurement of aspartame and vanillin. The metamaterial consists of an array of concentric aluminum rings on a polyimide substrate. A three-dimensional full-wave electromagnetic field simulation is performed using the finite integral method. The metamaterial transmission spectrum contains two dips at 0.39 THz and 0.61 THz. These two frequencies correspond to the characteristic absorption peaks of aspartame and vanillin in the THz band. According to the hybrid induced transparency (HIT) principle, introducing an additive on the metamaterial surface results in the appearance of a narrow transmission peak at the corresponding transmission dip, where the peak intensity increases with the additive thickness. The calculated sensitivity of the proposed metamaterial sensor is 30.76 dB/(ng/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) for aspartame and 63.91 dB/(ng/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) for vanillin. Specific detection is realized because the characteristic absorption peaks of different additives appear at different positions in the transmission spectrum. Therefore, the proposed THz metamaterial sensor has high application value in the field of food additive detection.

IMPEDANCE BOUNDARY CONDITION OF NON-UNIFORM ELECTROMAGNETIC FIELD PENETRATION INTO CONDUCTING HALF-SPACE

The influence of the non-uniformity of the external field to its distribution on the surface of the conducting half-space is investigated on the basis of exact analytical and approximate asymptotic calculation methods of an arbitrary three-dimensional electromagnetic field. The function that generalizes the impedance boundary condition for diffusion of non-uniform field into conducting body is proposed. On the basis of calculations results comparison by exact and approximate methods for concrete model of electromagnetic system the admissible value of the upper limit of the introduced small parameter is established. References 10, figures 5.

Erbium-ytterbium co-doped photonic crystal fiber amplifier supporting amplification for orbital angular momentum

In order to reduce the loss in orbital angular momentum (OAM) long-distance communication systems, an OAM erbium-ytterbium co-doped fiber amplifier (OAM-EYDFA) based on photonic crystal fiber (PCF) is proposed and investigated for the first time in this work. We set up a three-dimensional electromagnetic field model of the PCF in Comsol and solved it by the finite element method. Then, we designed a three-dimensional model of the OAM-EYDFA based on the proposed PCF using Comsol and MATLAB. The results reveal that the proposed OAM-EYDFA has a flat-high gain of about 47 dB, a differential mode gain of lower than 0.3 dB and a noise figure of lower than 3.4 dB. Compared with existing studies, its gain is increased by at least 25 dB, and other properties are also improved. The proposed OAM-EYDFA can provide a reference for OAM-based long-distance communication systems.

A Three-Dimensional Microwave Sparse Imaging Approach Using Higher-Order Basis Functions

This paper presents a novel method for three-dimensional microwave imaging based on sparse processing. To enforce the sparsity of the unknown function, we take advantage of the fact that arbitrary three-dimensional electromagnetic fields can be decomposed into two components with respect to the radial direction: one with transverse-magnetic polarization and the other with transverse-electric polarization. Each component can be further expressed as a sum of spherical harmonics, which provide the dictionary exploited by the sparse processing algorithm. Our measurement model relates the data and the parameters of the spherical harmonics’ sources, which are uniformly distributed on a grid sampling the imaging domain. By relying on the theory of degrees of freedom of electromagnetic fields, it can be shown that only a few harmonics are sufficient to accurately represent the measured scattered field from objects whose diameter is of the order of the wavelength, thus allowing reducing the dimension of the adopted dictionary. We analyze several imaging scenarios to assess the algorithm’s performance, including different object shapes, sensor orientations, and signal-to-noise ratios. Moreover, we compare the obtained results with other state-of-the-art linear imaging techniques. Notably, thanks to the adopted dictionary, the proposed algorithm can yield accurate images of both convex and concave objects.

Bioengineered Living Bone Grafts-A Concise Review on Bioreactors and Production Techniques In Vitro.

It has been observed that bone fractures carry a risk of high mortality and morbidity. The deployment of a proper bone healing method is essential to achieve the desired success. Over the years, bone tissue engineering (BTE) has appeared to be a very promising approach aimed at restoring bone defects. The main role of the BTE is to apply new, efficient, and functional bone regeneration therapy via a combination of bone scaffolds with cells and/or healing promotive factors (e.g., growth factors and bioactive agents). The modern approach involves also the production of living bone grafts in vitro by long-term culture of cell-seeded biomaterials, often with the use of bioreactors. This review presents the most recent findings concerning biomaterials, cells, and techniques used for the production of living bone grafts under in vitro conditions. Particular attention has been given to features of known bioreactor systems currently used in BTE: perfusion bioreactors, rotating bioreactors, and spinner flask bioreactors. Although bioreactor systems are still characterized by some limitations, they are excellent platforms to form bioengineered living bone grafts in vitro for bone fracture regeneration. Moreover, the review article also describes the types of biomaterials and sources of cells that can be used in BTE as well as the role of three-dimensional bioprinting and pulsed electromagnetic fields in both bone healing and BTE.

Modeling and analysis of three-dimensional quasi-stationary electromagnetic fields of non-contact inductometers placed above the conductive agricultural soil. Part ІІ

The paper is devoted to solving the problem of the theory of three-dimensional quasi-stationary electromagnetic field generated by a non-contact inductometer in its interaction with the electrically conductive agricultural soil located below it at some distance and whose specific electrical conductivity is measured. The peculiarity of this study is that it is based on obtaining an accurate analytical solution to the problem of an electromagnetic field created by an arbitrary spatial circuit with a current (contactless inductometer model) located near a magnetized electrically conductive body with a flat surface (agricultural conductive soil model). Solutions made by taking into account the closed circuits are found in the form of squares for vector and scalar potentials, magnetic and electric field strengths in an electrically conductive medium without restrictions on the geometry of the circuits, environmental properties, and field frequency. Having a precise solution, in addition to the indisputable advantage associated with the validity of the results found, allows obtaining a number of consequences that are valid for an arbitrary field in the system. Another important consequence of an accurate solution is the conclusion that an inhomogeneous electromagnetic field when penetrating into an electrically conductive space with depth always attenuates faster than a homogeneous field. For pulsed fields, the calculation is limited to a certain period of time from the beginning of the current pulse, and the closer to the initial moment of time, the more accurately the electromagnetic field is calculated. Since the current pulse usually changes the fastest and reaches its highest values in a relatively short period of time, it is at this most important stage that the electromagnetic field is determined.

Моделювання та аналіз тривимірних квазістаціонарних електромагнітних полів безконта-ктних індуктометрів, розміщених над електропровідним ґрунтом сільськогосподарського призначення. Ч. І.

The paper is devoted to solving the problem of the theory of three-dimensional quasi-stationary electromagnetic field generated by a non-contact inductometer in its interaction with the electrically conductive agricultural soil located below it at some distance and whose specific electrical conductivity is measured. The peculiarity of this study is that it is based on obtaining an accurate analytical solution to the problem of an electromagnetic field created by an arbitrary spatial circuit with a current (contactless inductometer model) located near a magnetized electrically conductive body with a flat surface (agricultural conductive soil model). Solutions made by taking into account the closed circuits are found in the form of squares for vector and scalar potentials, magnetic and electric field strengths in an electrically conductive medium without restrictions on the geometry of the circuits, environmental properties, and field frequency. Having a precise solution, in addition to the indisputable advantage associated with the validity of the results found, allows obtaining a number of consequences that are valid for an arbitrary field in the system. Another important consequence of an accurate solution is the conclusion that an inhomogeneous electromagnetic field when penetrating into an electrically conductive space with depth always attenuates faster than a homogeneous field. For pulsed fields, the calculation is limited to a certain period of time from the beginning of the current pulse, and the closer to the initial moment of time, the more accurately the electromagnetic field is calculated. Since the current pulse usually changes the fastest and reaches its highest values in a relatively short period of time, it is at this most important stage that the electromagnetic field is determined.

An efficient dual functional Raman and Fluorescence detection platform achieved by controlling the electromagnetic enhanced field in three-dimensional Ag/ZnO composited arrays

Integrating SERS and MEF into a single platform is a challenge. Here, we design a three-dimensional electromagnetic field via decorating Ag nanoparticles onto ZnO nanorod arrays to realize dual-function detection by SERS and MEF simultaneously.

On Maxwell Electrodynamics in Multi-Dimensional Spaces

The governing equations of Maxwell electrodynamics in multi-dimensional spaces are derived from the variational principle of least action, which is applied to the action function of the electromagnetic field. The Hamiltonian approach for the electromagnetic field in multi-dimensional pseudo-Euclidean (flat) spaces has also been developed and investigated. Based on the two arising first-class constraints, we have generalized to multi-dimensional spaces a number of different gauges known for the three-dimensional electromagnetic field. For multi-dimensional spaces of non-zero curvature the governing equations for the multi-dimensional electromagnetic field are written in a manifestly covariant form. Multi-dimensional Einstein’s equations of metric gravity in the presence of an electromagnetic field have been re-written in the true tensor form. Methods of scalar electrodynamics are applied to analyze Maxwell equations in the two and one-dimensional spaces.

Design of 1*4 Microstrip Antenna Array on the Human Thigh with Gain Enhancement

In this paper, at first attempted to design and simulate a stacked circular microstrip patch antenna for high gain at frequency 2.45 GHz, to apply on the industrial, scientific, and medical (ISM) applications. The antenna needs to be minimized for the array mounted on the human thigh, which has high gain and pattern scan capability. The substrate with a high relative permittivity is used for the designed antenna to minimize the dimension of the antenna. A 1*4 array antenna is designed for mount on the human thigh. The amplitude and phase of each antenna are obtained using the maximum-gain theorem to achieve the maximum gain of this array antenna. The coaxial feed is used to achieve good impedance matching, low cross-polarization, and easy control of the amplitude and phase of the element. For designing this entire array antenna, three-dimensional electromagnetic field simulation software Ansoft HFSS based on the finite element method is applied. To experimentally verify the performance, a prototype of the array antenna is fabricated and measurement is performed. The realized gain of the designed array antenna at the resonant frequency is 11 dB. This array structure can be mounted on a human thigh, waist, or head for medical applications, depending on the specific radius.

Design, Manufacture and Performance Evaluation of HTS Electromagnet Wound by YBCO Tape

Heat generation and serious energy consumption of normal-conductive suspension electromagnets influence the performance and stability of suspension systems. With the development of second generation (2G) high temperature superconducting (HTS) technologies, HTS suspension electromagnets are being considered for energy saving purpose. In this paper, a suspension system with three suspension electromagnets is designed, which is comprised of two normal-conductive suspension electromagnets and a 2G-HTS suspension electromagnet. A three-dimensional (3D) electromagnetic field simulation based on finite element method (FEM) is carried out, and the force test platform of suspension electromagnet is built for performance evaluation of the HTS suspension electromagnet. The experimental results show that the current of HTS suspension electromagnet is steady loaded from 0 A to 70 A under 77 K working conditions, with the suspension force meet the requirements. This work provides a certain theoretical and practical foundation for the future superconducting suspension projects.

Fabrication and Evaluation of a Magnetically Coupled EMI Filter Designed With Topology Optimization

In this article, topology optimization was used to design a magnetic core structure on a π-type filter circuit. The newly designed magnetic core canceled the noise generated by conducted and induced currents, and as a result, showed dramatically improved electromagnetic interference (EMI) filter performance. Topology optimization was executed using three-dimensional electromagnetic field analysis to capture the magnetic coupling effect. The designed magnetic core was fabricated by machined milling and its performance was evaluated by measuring the noise reduction effect of a simple EMI filter equipped with the core. The EMI filter equipped with our optimized magnetic core showed about 30 dB higher performance than a filter with conventional ring-shaped cores.These results show that the performance of an EMI filter can be improved by optimizing the structure of its magnetic core.

Two-point polarization correlations of random paraxial and nonparaxial electromagnetic fields

We investigate the two-point polarization correlation properties of random, statistically stationary, two-dimensional (2D) and three-dimensional (3D) electromagnetic fields. To this end two specific mutual polarization correlation functions are introduced, one based on a geometric approach using the Poincar\'e vectors and the other on the energy distribution employing the Jones vectors. Both approaches provide equivalent information about the space-time polarization correlations and enable one to associate with the field a polarization length over which the equal-time polarization states remain essentially unchanged. For fields obeying Gaussian statistics, the polarization correlation functions take on simple forms in terms of measurable quantities representing electromagnetic coherence. The formalism is demonstrated with two examples: blackbody radiation inside a cavity and in the far zone of a cavity wall aperture.