Electromagnetic Field Distribution Research Articles

Wavelength-tunable infrared chiral metasurfaces with phase-change materials.

Optical phase-change materials exhibit tunable permittivity and switching properties during phase transition, which offers the possibility of dynamic control of optical devices. Here, a wavelength-tunable infrared chiral metasurface integrated with phase-change material GST-225 is demonstrated with the designed unit cell of parallelogram-shaped resonator. By varying the baking time at a temperature above the phase transition temperature of GST-225, the resonance wavelength of the chiral metasurface is tuned in the wavelength range of 2.33 µm to 2.58 µm, while the circular dichroism in absorption is maintained around 0.44. The chiroptical response of the designed metasurface is revealed by analyzing the electromagnetic field and displacement current distributions under left- and right-handed circularly polarized (LCP and RCP) light illumination. Moreover, the photothermal effect is simulated to investigate the large temperature difference in the chiral metasurface under LCP and RCP illumination, which allows for the possibility of circular polarization-controlled phase transition. The presented chiral metasurfaces with phase-change materials offer the potential to facilitate promising applications in the infrared regime, such as chiral thermal switching, infrared imaging, and tunable chiral photonics.

ID: 221013 Optimizing Spinal Cord Stimulation Using a Novel Green's Function-Based Generalized Activating Function

Prior work has shown that patient-specific computational modeling and optimization of epidural electrical stimulation (EES) of the spine can be used to rapidly restore locomotion in paraplegics [1]. To this end, Rowald et al. describe a pipeline for generating detailed spine models from medical imaging data. For a given model, electromagnetic field distributions are calculated for the activation of each electrode contact and coupled to electrophysiological simulations of axon populations within each root and rootlet. Optimal exposure conditions for the safe and selective activation of target roots may thus be identified.

A High-Quality Optical Sensor with High Resolution Based on Coin-like Resonator

A nanoscale plasmonic temperature sensor via a metal-insulator-metal (MIM) structure is proposed in this paper, and the waveguide structure is composed of a coin-like resonator. The finite element method (FEM) is used to study the structure’s transmission characteristics and electromagnetic field distributions. The calculated maximum temperature sensitivity is about 0.38 nm/°C, and the figure of (FOM) merit can be as high as 30,158, higher than most of the published MIM structure research. Compared to the structure without a square resonator, the FOM is enhanced by about 479%. We believe the proposed sensor can be a promising platform for future sensing applications such as filters, absorbers, and splitters.

A Review of the Computational Investigation of Three-Dimensional Transient Magneto-Thermal Coupling Characteristics of Electromagnetic Railgun Armature and Rail in High-Speed Sliding Electrical Contact

In order to investigate the dynamic process of electromagnetic field distribution, temperature change and the deformation during the launching process of electromagnetic railgun. It is necessary to conduct a three-dimensional coupled electromagnetic-temperature-structure analysis of the rail and armature, which requires the establishment of the corresponding multi-physics field model and the use of appropriate software and algorithms to complete the relevant simulation calculation and solution results. Based on this, this paper summarizes the current domestic and foreign research methods for multi-physics field characteristics under sliding electrical contact conditions, analyses the advantages and disadvantages of each method, and focuses on the updates of the three-dimensional finite element program EMAP3D based on Lagrangian description and the advantages of multi-field coupling. Finally, several considerations and operable spaces for multi-physics field coupling simulation are summarized to provide technical support for subsequent studies on multi-physics field characteristics for high-speed sliding electrical contact condition.

Analysis of Power Transfer Characteristics of IPT System With Near Field Magnetic Coupling

This article investigates the working principle of the inductive power transfer (IPT) system from the perspectives of electromagnetic field distribution. According to the limitations of frequency and transmission distance, it is proved in this paper that the IPT system works in the near field, where the energy density of the magnetic field is much stronger than that of the electric field. Therefore, only the magnetic field in the IPT system needs to be considered in approximate power analysis. The mutual inductance model of the IPT system is an approximate and simplified form of the electromagnetic field model. The complex form of the Poynting vector of the IPT system is integrated over an intermediate infinite plane of the two coils to reveal the power transfer characteristics including the active and reactive power. When the system is in full resonance, only active power is transferred without reactive power, which is consistent with the results obtained from the circuit model. This article is useful to provide an insight into the power flow and energy distribution of the IPT system.

Research on electromagnetic coupling characteristics of UAV circuits in the Complex electromagnetic environment

The overall circuit model and Complex electromagnetic environment model of a typical UAV are built to explore the survivability of multirotor in the complex electromagnetic environment. The composite theoretical calculation model of the metal cavity aperture coupling and internal circuit coupling is constructed using the established UAV circuit model, which is based on the equivalent magnetic dipole algorithm and the FDTD algorithm. The terminal coupling voltage in the UAV circuit and the electromagnetic field distribution inside the metal cavity are estimated. CST software is used to simulate the response of UAV circuits in the same condition, and the correctness of the theoretical calculation model is confirmed. Then, the terminal coupling voltage of the PCB is used to create an electromagnetic coupling efficiency model. The findings reveal that the constructed composite theoretical model can accurately characterize the electromagnetic coupling characteristics of UAV circuits in the complex electromagnetic environment, with an error range of 1%~8%. When comparing the terminal coupling voltage of PCB in various complicated electromagnetic environments, the High-power microwave (HPM) has the maximum coupling efficiency. HPM initially causes the UAV circuits to attain the damage threshold under identical event conditions and target specifications. The findings could be used as a guide for multirotor circuit board protection in the complex electromagnetic environment, as well as for the development of high-power electromagnetic pulse weaponry.

Design of embedded metamaterial solar absorber based on genetic algorithm

To effectively collect the solar energy, a metamaterial solar absorber operating in the UV to NIR wavelength range is designed, which consists of an embedded structure stacked with Ti and SiO2. The embedded structure can enhance the magnetic and electric fields to improve the absorption rate. However, the parameter space of the embedded structure is very huge to increase the optimization search time. Therefore, the absorption rate is calculated by the finite difference time domain method and the parameters of the absorber are optimized by genetic algorithm. The results show that the absorption rates of the optimized absorber are all over 95% in the 300–2500 nm and the average absorption rate is 98.7%, and the absorber is of polarization independence and the average absorption rate remains above 95% at an oblique incidence angle of 60°. By analyzing the electromagnetic field distribution of the absorber at the resonance wavelength, it can be concluded that the high absorption characteristics in the wideband are mainly achieved by the combined effects of local surface plasmon resonance, electric dipole resonance, propagating surface plasmon resonance and Fabry-Perot cavity resonance. Perfect absorber in the solar spectral range have significant value in fields such as solar energy harvesting and information detection.

Analysis of the Influence of Remanence on the Performance of Current Transformer Caused by DC Ice Melting of Transmission Lines

This paper theoretically analyzes the performance changes of the measuring winding and protective winding of the current transformer behind the iron core of the DC ice melting current magnetized transformer. According to the actual ice melting situation, a finite element simulation model is established to calculate the electromagnetic field distribution inside the transformer, quantify the remanence generated by the ice melting, and design a verification test to measure the remanence and transmission characteristics of the current transformer after the ice melting current is magnetized. Based on theory, simulation, and experiment, suggestions for the treatment after ice melting are put forward.

Ultra-Broadband Solar Absorber and High-Efficiency Thermal Emitter from UV to Mid-Infrared Spectrum.

Solar energy is currently a very popular energy source because it is both clean and renewable. As a result, one of the main areas of research now is the investigation of solar absorbers with broad spectrum and high absorption efficiency. In this study, we create an absorber by superimposing three periodic Ti-Al2O3-Ti discs on a W-Ti-Al2O3 composite film structure. We evaluated the incident angle, structural components, and electromagnetic field distribution using the finite difference in time domain (FDTD) method in order to investigate the physical process by which the model achieves broadband absorption. We find that distinct wavelengths of tuned or resonant absorption may be produced by the Ti disk array and Al2O3 through near-field coupling, cavity-mode coupling, and plasmon resonance, all of which can effectively widen the absorption bandwidth. The findings indicate that the solar absorber's average absorption efficiency can range from 95.8% to 96% over the entire band range of 200 to 3100 nm, with the absorption bandwidth of 2811 nm (244-3055 nm) having the highest absorption rate. Additionally, the absorber only contains tungsten (W), titanium (Ti), and alumina (Al2O3), three materials with high melting points, which offers a strong assurance for the absorber's thermal stability. It also has a very high thermal radiation intensity, reaching a high radiation efficiency of 94.4% at 1000 K, and a weighted average absorption efficiency of 98.3% at AM1.5. Additionally, the incidence angle insensitivity of our suggested solar absorber is good (0-60°) and polarization independence is good (0-90°). These benefits enable a wide range of solar thermal photovoltaic applications for our absorber and offer numerous design options for the ideal absorber.

Имитационное моделирование воздушных линий электропередачи напряжением 610 кВ для исследования алгоритмов определения места возникновения однофазных замыканий на землю

As part of evolution of single phase to earth faults protection methods and tools in 6–10 kV networks the development of simulation study methods of these networks and their components becomes relevant. A significant direction in this area is upgrading of sensors installed directly on the wires and electrical transmission towers. These sensors are installed in the conditions of an electromagnetic field acting on them and dynamically changes both in time and space, especially during emergency modes including single phase to earth faults. Application of modern software offers a challenge for complex simulation study of electromagnetic fields distribution at the location of the measuring transducers in continuously variable electromagnetic environment. The above-noted statement determines the relevance of the research goal, which is the development of a simulation study method of 6–10 kV overhead power lines, the model of which is designed to study existing and create new single phase to earth fault location algorithms and devices. To solve the tasks set the methods of simulation study of overhead transmission lines and corresponding medium voltage networks in PSCAD and COMSOL Multiphysics software have been used. The general concept of design of a 6–10 kV network and an overhead transmission line simulation model is formulated. The geometrical parameters of the section of the model of an overhead power transmission line to simulate electromagnetic transients are selected, considering the frequency dependence of the line parameters (inductance and active resistance). The proposed model of the overhead transmission line is verified, and recommendations for its application are given. The developed “inductive” component of the proposed overhead transmission line model allows to provide high accuracy of calculation of transient components of currents and voltages during single phase to earth faults. It makes possible to use this model for the development and research of single phase to earth fault location algorithms. The developed approach to simulation study of an overhead transmission line is the field of interest for further research, as it makes it possible to calculate the components of the electric field which are observed during single phase to earth faults.

Design of a simple side-incident TE11 mode microwave probe for nondestructive pipe inspection

This study proposed a simple side-incident TE11 mode microwave probe for the rapid and long-range inspection of cracks in metallic pipes. The probe feeds the microwaves to a metallic pipe, which works as a waveguide; the reflection signal provoked by a defect is measured for detection and localization. The probe enables the detection of both circumferentially and axially oriented cracks, unlike those reported in earlier studies. To achieve better performance, numerical simulations were conducted to evaluate the conversion efficiency and optimize the insertion length of the coaxial cable and the exposed length of the cable core wire. The simulation results suggest that the optimized probe configuration is feasible for pipes with various diameters by proportionally changing the current probe configuration. Although injected microwaves propagated in two directions, the ratio of microwaves to one direction could be controlled by adjusting the inclination angle and the exposed length of the cable core wire. Subsequently, three TE11 probes fabricated according to the simulation results were used to detect circumferential and axial slits in a brass pipe. The results showed that circumferential slits in the vertical positions (parallel to the nontilted coaxial cable) and axial slits in the horizontal positions (perpendicular to the nontilted coaxial cable) caused large reflections, consistent with the electromagnetic field distribution of the TE11 mode microwaves in a circular waveguide. Further experiments verified the feasibility of the designed probe for pipes with different diameters and for directional pipe inspection.

Transient Electromagnetic Smoke Ring Due to a Grounded-Wire Source

The concept of a “smoke ring” in electromagnetic fields can be used to describe the spatial distribution and diffusion of electromagnetic fields with either frequency or time. This provides an intuitive basis for the qualitative interpretation of artificial-source electromagnetic measurement results. The existing discussions regarding this field of study have mainly focused on the smoke rings of a magnetic dipole or loop source. In the present work, smoke rings of other commonly used grounded-wire sources in the time domain are investigated. The results show that the smoke ring of grounded-wire sources is more complex than that of magnetic sources. A grounded-wire source can generate an induced current in both horizontal and vertical directions. The horizontal induced current includes positive and negative parts. Both parts of the horizontal induced current maximum diffuse downward perpendicular to the surface, but the diffusion velocity of the negative part is faster, approximately 5.6 times that of the positive part. The vertical induced current maximum diffuses at 45° from the grounded surface with a velocity approximately 5 times that of the positive horizontal induced current. The smoke ring of the horizontal induced current closely resembles a basin, while that of the vertical induced current is more similar to two separate cylinders. Finally, the imaging depth based on horizontal and vertical induced currents is obtained by the statistical relationship between the induced current maximums and the diffusion depth, which are equal to 1.4 times and 1.25 times the diffusion depth, respectively.

Enhancing light extraction efficiency of GaN LED by combining complex‐period photonic crystals with doping

AbstractThe light extraction efficiency (LEE) of GaN‐based light‐emitting diodes (LEDs) was limited by intense total internal reflection and the photothermal effect. In order to solve this problem, a method to synergistically control the LEE of GaN‐based LEDs by ​​combining the complex‐period photonic crystals (PhCs) with M (M = Al, In) material doping is proposed. The forbidden band width of two‐dimensional (2D) PhC array, three‐dimensional (3D) LED model, M doping, and electromagnetic field distribution are investigated respectively. By doping the M, the LED emission wavelength range is regulated to achieve the dual‐band emission. Furthermore, a triangular complex‐period photonic structure is introduced to establish stacked or etched PhCs models. By combining the plane wave expansion and finite difference time domain algorithm, the structural parameters of PhCs and M concentration dependent LEE are investigated, and the electromagnetic field distribution is explored also. The results show that the optimal LEEs can be achieved are 19.08% and 13.96% for blue light and ultraviolet, respectively, which are larger than that of traditional flat‐panel LED (4%). This work provides theoretical results and technical support for the design of LEDs with high luminous efficiency.

Design and measurements of 6 x 6 m collimator reflector with rounded edges

Compact antenna test range (CATR) is designed to form a plane wave at a small distance from the aperture of the collimator reflector, which allows measurements to be made under far field conditions in a compact anechoic chamber. Currently, collimators are in demand due to the technical re-equipment of the industry for the production of 4G, 5G and Internet of Things stuff. The typical size of a quiet zone for these needs is 1–1.5 m. Along with antenna pattern measurements, collimators are widely used for RCS measurements. In the latter case, the measured objects may have dimensions several times larger than the average size of the quiet zone. Manufacturing, installation and adjustment of collimator reflector of several meters in size is a non-trivial task that requires separate study for each project. An incorrect choice of the reflector geometry can lead to an increase in mass and size, which entails an increase in production costs and the anechoic chamber designed for the CATR. In addition, increase in mass imposes additional requirements on the rigidity of the rack to which the reflector is attached, and the foundation under the collimator. As a rule, large-sized reflectors consist of a dozen fragments, which leads to the need to have special adjustment mechanisms for precision tuning of the reflector fragments. These and other problems need to be solved when developing large CATR. The article presents the issues faced by the LLC «RadioLine» in the process of manufacturing and setting up a collimator stand with a 6 x 6 m reflector. The issues of choosing the geometry of the reflector, its focal length have been highlighted. It has been shown how the agreement of the results of three-dimensional modeling of the reflector and production capabilities has been carried out. The features of the design of the reflector rack are touched upon, in particular, the appropriateness of using two materials: one for the base, and the second for the truss, which is connected to the reflector. After discussing the design features, a scheme for measuring the electromagnetic field distribution in a quiet zone, approaches to improving the quality of the RF characteristics of the CATR have been presented. It is noted that in the process of setting up the collimator, in order to determine the directions to the sources of diffraction, it is useful to apply the recalculation of the measured electromagnetic field in the quiet zone into the plane wave spectrum. At the end of the article, quiet zone cuts have been shown at frequencies of 0.75 GHz, 8.2 GHz and 50 GHz. Average peak-to-peak ripple of the amplitude-phase distribution in the operating frequency range of the CATR is 1 dB in amplitude and 10 degrees in phase.

Ultra-fast all-optical 8-to-3 encoder utilizing photonic crystal fiber

This work proposes a novel design of an 8-to-3 encoder in a photonic crystal fiber (PCF). It is composed of a buffer and three OR logic gates using circular air holes in a silicon dioxide substrate. We have employed the plane-wave expansion technique to analyze the band structure of the proposed PCF and the beam propagation method to study the transmission efficiency and electromagnetic field distributions. Our findings reveal that the encoder operates well within the main third telecommunication window, which corresponds to 1530–1565 nm. The numerical calculations show that transmissions greater than 70% and less than 0.05% are logics 1 and 0, respectively. The proposed encoder has a maximum delay of 7.5 ps, and its total footprint is about 140 µm × 14 µm × 3 mm. This makes the proposed PCF-based encoder suitable for simple and low-cost fabrication, which may find applications in optical communication devices and integrated circuits.

Adjustment of eccentricity and split angle for improved SERS and refractive index sensing of TiN nanodonuts

The unique refractory plasmonic properties and strong enhancement of the electric field within the inherent gap of titanium nitride (TiN) nanodonuts make them excellent candidates for surface-enhanced Raman scattering (SERS)- and refractive index (RI)-sensing applications. The eccentricity and split angles are critical parameters for tuning the localized surface plasmon resonance (LSPR) properties of the donuts, which were numerically investigated using the finite element method herein. We demonstrated that the proposed donuts provided efficient SERS and RI sensing substrates capable of working in regions ranging from ultraviolet (UV) to near-infrared (NIR). By adjusting the eccentricity and split angles, the corresponding optimized RI sensitivity and SERS enhancement factor reached 1,374 nm RIU−1 and 6.8 × 104, respectively. Moreover, the effects of both incident polarisation and electromagnetic (EM) field distributions on the LSPR properties were elucidated and discussed. This study provides new insights for understanding the LSPR properties of TiN nanoparticles and enables the rational design of efficient refractory plasmon-based SERS and RI-sensing substrates.

Experimental, analytical and numerical study of the electromagnetic field distribution in pulsed power plasma stimulation (PPPS)

Electromagnetic (EM) field generated during a pulsed power plasma discharge (PPPD) laboratory experiments was matched against an analytic solution, and numerically using a finite element module of the COMSOL RF software. The EM field was calculated during and after the plasma pulse. Agreement between the numerically and analytically calculated EM field with laboratory experimental measurements provides support for extension of the model to a larger scale and eventually to reservoir scale. The validated model was used to quantify the signal attenuation level in different media. The results of the comparative model show that different environments around the sample will have more impact on magnetic field transversely (perpendicular plane of current direction) than longitudinally within the sample domain. Existence of water (with higher electric permittivity) plays important role in signal penetration depth away from the source signal. This preliminary model provides the framework for future design of lager scale electromagnetic simulation of PPPS (Pulsed Power Plasma Stimulation) technique as source signal at various design configurations.

Analysis of Electric Transmission Failure Induced by Electrostatic Migration and Deposition of Abrasive Dusts in SADA

The electric transmission failure induced by the electrostatic migration and deposition of the friction-pair-produced abrasive dusts in the Solar Array Drive Assembly (SADA) is studied for the first time by integrating experiments and Finite Element Method (FEM) simulation. Particle morphology and composition are characterized by SEM and X-ray EDS, respectively. The size, distribution and average charge of the abrasive dusts are characterized by PSDA as well as the home-made particle charge measurement device. The results show that the dusts’ sizes are in the range of 10–40 μm, and the dusts are primarily composed of Ag and a small amount of Cu and S. Sliced abrasive dusts with an average diameter of 30 μm and a charge of 85 e are used for the FEM prediction of particle trajectory, which is consistent with the theoretical calculation results. The electromagnetic field distribution in the SADA and the electrostatic migration and deposition of abrasive dusts are predicted and analyzed by adopting the FEM method. The experimentally observed dusts’ trajectories in a vacuum chamber with 0.02 Pa vacuum degree are consistent with the simulation results, which qualitatively verifies the accuracy of the FEM model. The predicted results show that the irradiation-induced conductivity increase in polyimide material has little influence on the electric field distribution and the migration and deposition of the abrasive dusts but has great influence on the local current density. Both the potential differences between the two adjacent conducting rings and the loose contact between the electric brush and the conducting rings have significant influence on the migration and deposition of the abrasive dusts, which may greatly increase the surface discharge risk and the electrical transmission instability in the SADA. This study is conducive to the safe and stable operation of the on-orbit spacecrafts.

Research on Material Selection and Electromagnetic Characteristics of Composite Electromagnetic launcher

The armature and rail thermal ablation caused by the current concentration phenomenon will affect the service life of the guideway during the operation of the compound four-rail electromagnetic emitter. With different rail materials simulated and analyzed using the finite element analysis method and the ANSYS software, the composite four-rail electromagnetic launcher’s current density distribution and electromagnetic field distribution were designed to optimize and improve the thermal ablation of the armature and rail of the composite electromagnetic launcher. The results show that the copper steel composite electromagnetic launcher can improve the current concentration and electromagnetic shielding ability.

Design and Study of the Key Characteristics of a New DC Vacuum Interrupter With a High Peak and Low Residual Magnetic Field

With the rapid development of multiterminal high-voltage direct current (HVdc) transmission systems, the research and development of high-speed and stable high-voltage dc circuit breakers have received attention. Among them, mechanical dc circuit breakers based on manual zero-crossing dc breaking technology have been applied in practical projects, owing to their small size, low on-state loss, and low price. However, this method adds a high-frequency current, which deteriorates the magnetic field between the poles of the interrupter when the arc is broken. Therefore, the development of HVdc circuit breakers that maintain high peak magnetic fields and low residual magnetic fields at high frequencies has become the key to the development of multiterminal HVdc transmission. To solve this problem, this article proposes a new interrupter for a vacuum dc circuit breaker based on artificial zero-crossing technology and studies its key characteristics, such as temperature rise, electromagnetic field, and arc column plasma distribution characteristics. The results reveal that the new interrupter proposed in this article has a low-temperature rise, uniformly distributed electric field, high peak value and low remanence of the longitudinal magnetic field, and uniformly distributed plasma in the arc column, and exhibits arc diffusion. Its ability to cope with high-frequency current is significantly higher than that of the traditional cup-shaped axial magnetic field (AMF) contact system interrupter, which is conducive to the high-speed and stable breaking of the interrupter.