Analysis Of Field Distribution Research Articles

Fabrication of patterned TiO2 nanotube layers utilizing a 3D printer platform and their electrochromic properties

Anodization enables nano-structure fabrication through electrochemical parameter control. While various approaches exist for creating localized or patterned oxide layers, many are complex and time-consuming. This study adopted a commercial 3D printer for high-speed (1 mm/s) anodization, forming TiO2 nanotube layers on Ti substrates in G-code-designed patterns. Comprehensive characterization using XRD, SEM, XPS, and simulated electric field distribution analysis revealed well-defined nanostructures and provided insights into the formation mechanism. Furthermore, viologen-anchored TiO2 showed significantly improved electrochromic performance compared to pristine TiO2, with a higher reflectance difference (46.2 % vs. 6.85 %). This 3D printing-anodization hybrid method offers a rapid approach to fabricating patterned TiO2 nanostructures, showing promise for electrochromic devices with enhanced optical modulation capabilities.

Investigation of aerodynamic processes in porous materials based on triply periodic minimal surfaces

RELEVANCE: The relevance of this work lies in the study of new porous materials for use in compact, highly efficient heat exchange devices. PURPOSE: To investigate the hydro-aerodynamic properties of flows passing through porous inserts based on triply periodic minimal surface (TPMS) topologies. To develop a methodology for studying porous materials with ordered structures. To identify potentially suitable TPMS-based porous materials for application in heat exchange equipment. METHODS: Numerical (CFD) and experimental methods were used to address the research objectives. Ansys Fluent 2019 R3 software was utilized for numerical modeling. Experimental samples for the physical experiments conducted on the VENT-08-7LR-01 laboratory setup were fabricated using SLA additive technologies. The porosity of the samples ranged from 0.73 to 0.89. The experiment was conducted with inlet velocities ranging from 0.3 to 4.5 m/s. RESULTS: New empirical dependencies of pressure drop on flow velocity were obtained for inserts based on the surfaces: Primitive (P), Fischer Koch S (FKS), Neovius (N), and Schoen's I-WP (IWP). The airflow through the N structure showed the highest pressure drop, while the P structure had 8 times less pressure drop at the same velocity. Stagnation zones, which can negatively impact heat transfer, were identified in the porous inserts. Changes in local flow velocity in the porous inserts were determined to correlate with the insert's transparency. CONCLUSION: The research results can be used for designing cooling systems with TPMS-based ribbing. Based on the analysis of the velocity vector field distribution and pressure drops, the FKS and IWP structures have potential applications in heat exchange equipment.

Nanostructures/TiN layer/Al2O3 layer/TiN substrate configuration-based high-performance refractory metasurface solar absorber

Metasurface solar absorber serves as a kind of important component for green energy devices to convert solar electromagnetic waves into thermal energy. In this work, we design a new solar light absorber configuration that incorporates the titanium nitride substrate, aluminum oxide layer, titanium nitride layer, and the topmost refractory nanostructures. The metasurface absorber based on this configuration can achieve an average spectral absorption of over 91% and a total solar radiation absorption of 91.5% at ultra-wide wavelengths of 300–2500 nm. It is discovered that the excellent performance of the proposed metasurface absorber is attributed to the synergistic effects of surface plasmonic effect and Fabry–Pérot (FP) cavity resonance by comprehensive analysis of the simulated field distributions. Furthermore, the effect of geometrical parameter of the proposed configuration on absorber performance is studied, indicating the proposed configuration possesses a large fabrication tolerance. Moreover, the proposed configuration is not sensitive to the polarization direction and the angle of incident light. It is also found that the use of other refractory metal materials and other shapes as the topmost absorbent nanostructures also have good results with this configuration. This work can offer a universal platform for constructing and guiding the design of refractory metasurface solar absorbers.

A Tunable Transparent Graphene Absorber with Multifrequency Resonance

AbstractThe demand for multinarrowband absorber has attracted increasing interest among researchers in recent years. However, integrating multifrequency absorption, tunability, and high optical transparency into an absorber remains a crucial challenge. In this study, a multiband, tunable, and transparent microwave meta‐absorber is theoretically proposed and experimentally demonstrated. This meta‐absorber is composed of resonant patterns made from graphene and indium tin oxide (ITO), placed on a substrate of lithium niobate (LN). By introducing P‐type doping to reduce the resistance of monolayer graphene to around 300 Ω, the impedance matching of the absorber is promoted, consequently manifesting ten absorption points within 40 GHz. The electric field distribution analysis and an equivalent circuit model are employed to elucidate the physical mechanisms of the multiband absorber. Additionally, the lithium niobate dielectric layer possesses a substantial dielectric constant and exhibits phase transition characteristics with temperature changes. When the temperature increases to 250 °C, a comprehensive tuning range of more than 5.49 GHz within 40 GHz range is realized. The maximum tuning range for a single frequency point is 1.33 GHz. With the broadening of the band, the meta‐absorber can provide multiple tunable ranges, making it more favorable for practical applications in optical modulator and sensor.

Switchable phase modulation and multifunctional metasurface with vanadium dioxide layer

Abstract Metasurface, comprising subwavelength unit cells, offers a flexible modulation of the optical phase. However, traditional metasurfaces are typically engineered to function solely in one mode, limiting their efficiency and adaptability. In this study, we proposed a switchable metasurface consisting of gold bars deposited on polyimide and vanadium dioxide (VO2) layer. Upon the phase transition of VO2, this switchable metasurface exhibits functionality in both transmissive and reflective modes. Specifically, it efficiently converts left circularly polarized (LCP) light into right circularly polarized (RCP) light. For the dielectric (metallic) phases of VO2, the design behaves as metalens with a focal length of 1000 (906) μm at working frequency of 1.2 THz, respectively. Furthermore, the vortex phase can be effectively manipulated with topological number from 1 to 4 through the analysis of the electric field distribution. A directional emission from 12.9° to 42.2° is obtained in the reflective mode and Airy beam paths way can also be well regulated at 1.49 THz. The phase modulation is further achieved by varying the inter-mediums and its thickness. Finally, the sensing ability is explored with different covered solution. Consequently, this multifunctional and adaptable metasurface offers valuable insights for the development of reflectors, modulators, lenses and sensors.

Research on Regulation Method of Variable-Air-Volume Air Conditioning System with “Personal Space”

In large public facilities, such as airport terminals or open-plan office spaces, the HVAC system typically consumes substantial amounts of energy. However, individuals often gather at specific areas while other zones are occupied by transient or occasional users. To minimize operational energy usage, this paper aims to reduce thermal comfort demands in non-targeted areas. This paper introduces a method for regulating the thermal environment around occupants exclusively in the variable-air-volume (VAV) air conditioning running mode. The investigation utilizes Airpak modeling and experimental verification techniques. Additionally, an analysis of temperature field and velocity field distributions within the room under the “personal space” operation mode is presented. The results suggest that adjusting the numbers of air vents, openings, airflow velocities, and air supply orientations can establish a comfortable thermal environment for inhabitants and reduce the overall ADPI value. The combined air supply mode leads to a 16.7% reduction in power usage compared to traditional full-space operation.

Investigation of magnetic domain interactions and switching mechanism in sputter deposited Fe–Co–Al thin film

To create a high-density data storage system, a thorough understanding of magnetic domain interactions is essential. In this work, we present a systematic study of magnetic domain state interaction and switching mechanism of Fe–Co–Al films across various thicknesses. Structural analysis confirms the formation of an A2-type disorder structure. Magnetic investigation reveals that all films are soft magnetic in nature, exhibiting a predominant in-plane magnetic anisotropy with a low coercive field that increases from 1.9 mT to 3 mT as the film thickness grows from 5 nm to 25 nm. Analysis of first-order reversal curves reveals the formation of multi-domain (MD) states. An enhancement of magnetic domain interactions occurs as the contour graph shifts along the coercive field direction with an increase in film thickness. Switching field distribution (SFD) analysis reveals broader SFD curves, indicating more inter-grain interactions as magnetostatic interactions between magnetic grains intensify with thickness. Further, magnetic force microscopy analysis confirms the presence of MD structures in all films. Magnetization reversal dynamics elucidates domain wall pinning near to zero field and possesses a large out-of-plane switching field. Simulations are performed to corroborate experimental findings. These findings underscore the critical role of domain state configuration and switching mechanisms for designing spintronic devices using soft magnetic thin films.

Terahertz tunable quasi-bound state in the continuum metasurface with high sensitivity based on Dirac semimetal

We have proposed a novel tunable terahertz (THz) quasi-bound states in the continuum (BIC) metasurface based on Dirac semimetal (DS). By modifying the structural parameters of the DS resonator and disrupting the C4 symmetry to induce perturbations, we achieve the conversion of BIC to quasi-BIC with a high Q-factor, reaching up to 1291.3. Moreover, we conducted a systematic analysis of the electric field distribution and surface current density for both symmetric and asymmetric configurations to elucidate the formation mechanism of the quasi-BIC. Furthermore, by varying the Fermi energy of the DS within the range of 0.1–0.2eV, we achieved continuously tunable operation with the operating frequency ranging from 1.179 to 1.248 THz and the transmission from 21.18% to 96.87%. Most notably, we investigated the sensing performance of the device, finding that its refractive index sensitivity and figure of merit (FOM) are 0.301 THz/RIU and 143.3 RIU−1, respectively, highlighting its potential for high-sensitivity applications, particularly in material detection and biomedical diagnostics.

Three-dimensional numerical simulations and experimental studies on the viscoelastic rheological and deformation behavior of polymer catheter in gas-assisted extrusion processing

Gas-assisted extrusion is an effective method for improving the deformation behavior of polymer catheters during extrusion. However, the underlying mechanisms that dictate how geometrical and constitutive models influence the complex rheological behavior of the melt are not yet fully understood, which hinders further utilization and optimization. In this study, the three-dimensional (3D) gas–liquid–gas model for catheter gas-assisted extrusion was constructed. Subsequently, the Bird–Carreau model and the Phan–Thien–Tanner (PTT) model were employed in finite element numerical simulations to analyze the complex behavior. For comparative analysis, simplified two-dimensional (2D) model numerical simulations were also conducted. Additionally, experiments on catheter gas-assisted extrusion and parameterization studies of key constitutive model parameters were performed. The findings indicate that the 3D model, when integrated with the PTT constitutive model, demonstrates superior predictability and aligns more closely with experimental results. Furthermore, as the flow rate increases, discrepancies among different models diminish, and the distance required for the melt and gas to achieve motion equilibrium decreases. The internal mechanisms behind these phenomena are elucidated through the analysis of velocity and stress field distributions. This research enhances our understanding of the complex rheological behavior in polymer catheter gas-assisted extrusion, providing valuable insights for both academic research and industrial production in this field.

Temperature Field Distribution and Thermal Stress Analysis of Pumped Storage Electric Motors

Abstract With the increasingly important role of pumped storage in energy systems, new and higher requirements have been put forward for the operation, safety, and economy of pumped storage power plants. The article takes a three-phase salient pole synchronous pumped storage motor as the research object, by using ANSYS finite element analysis software, a finite element model of a three-phase synchronous generator motor was established to analyze the internal temperature field distribution and thermal stress distribution of the motor. The results show that the higher temperature region of the entire system was concentrated at the winding, followed by the stator and rotor. Therefore, when optimizing the design of the motor in the future, the first step should be to start from the winding. The analysis of the thermal stress situation of the stator shows that the thermal stress and strain were mainly distributed at the inner diameter of the stator core, which was consistent with the distribution of the temperature field at the stator. The results of this study can provide theoretical guidance for the key maintenance areas and maintenance time of pumped storage power generation motors.

Performance enhancements of HTS power cables by minimizing the electric field enhancements for electric transport applications

Abstract Design innovations to manage the electric field enhancements and successful use of cryogenic epoxy EP37 as electrical insulation for high temperature superconducting (HTS) cables for electric aircraft applications are reported. Detailed finite element analysis (FEA) of the electric field distribution shows that the highest electric field is at the interface of the ground and electrical insulation layers. The FEA led to the design, fabrication, and experimental characterization of four model cables with stress cones and a direct bond of the ground and insulation layers. Enhanced partial discharge inception voltage (PDIV) was achieved in the model cables by minimizing the electric field enhancements at the ground layer interface. Using a helium gas mixture with 4 mol% H2, with higher intrinsic dielectric strength than pure helium, further enhanced the PDIV. The results warrant further studies on long HTS cables with EP37 as electrical insulation with a direct bond between the insulation and ground layers.

Measurement and evaluation of the flashover voltage on polluted cap and pin insulator: An experimental and theoretical study

This study investigates the flashover voltage on high voltage insulators in polluted environments, employing a combination of experimental and theoretical approaches. Utilizing Analysis of Variance (ANOVA) and the Finite Element Method (FEM), the research aims to offer a thorough comprehension of the phenomenon. The experimental aspect of the study involves subjecting insulators to polluted environments, replicating real-world scenarios, and measuring the resulting flashover voltages. This experimental study focuses on investigating flashover pollution, where artificial pollution is introduced into an experimental model. An observational approach is employed to assess the impact of conductivity and pollution distribution on the 1512 L cap and pin insulator, as well as its proposed experimental model. Complementing the experimental approach, the theoretical aspect of the study employs the FEM method to simulate and model the insulator's behaviour under pollution. This computational technique enables a detailed analysis of the electrical field distribution, surface potential, and stress repartition across the surface of the insulator. Simulations further explore the impact of pollution on flashover voltage and leakage current. The FEM results are then compared with experimental findings to validate the model's accuracy and reliability. By analyzing the collected data, the ANOVA technique is applied to identify significant differences in flashover voltage under diverse pollution levels. This statistical approach allows for the determination of the most influential factors affecting insulator performance. This research offers valuable insights into the influence of flashover voltage on high-voltage insulators in polluted environments, contributing to the development of more robust and efficient insulation systems. The combination of ANOVA and FEM methods provides a robust framework for understanding and predicting insulator performance, ultimately benefiting the power industry and promoting energy sustainability.

Multi-factor coupling analysis of electric field distribution in electrochemical machining with electrolyte suction tool

Electrochemical machining (ECM) technology holds significant potential for applications in high accuracy engineering and manufacturing. To confine the electrolyte region during ECM and mitigate the effects of reaction products and heat generation, an electrolyte suction tool has been proposed. However, the complex electric field distribution on the anode surface during the application of pulse voltage, limits the further utilization of ECM with suction tool. A multi-physics simulation model is established to calculate the region of electrolyte confinement by the suction tool, current density distribution within the electrolyte region, and material removal. The model considers the combined effects of polarization and double layer, and all key parameters are calibrated through classical electrochemical testing experiments rather than fitted based on the predicted results. This study elucidates the transient response of current density on the anode surface during the application of pulse voltage. The simulation accuracy is validated by comparing experimental and simulated current waveforms, as well as material removal profiles under different pulse parameters and electrode shapes. This research is of great significance for improving surface precision and controllability of complex structures in ECM with suction tool, promoting its further application in the field of precision machining.

Asymmetric transmission for linearly polarized terahertz waves without polarization conversion

In this study, a novel metamaterial (MM) architecture is presented, which comprises cut wires and split-ring resonators (SRRs) and demonstrates asymmetric transmission characteristics. Unlike previously reported multi-layer chiral structures, spatial asymmetry is introduced by aligning the cut wires and SRRs with the propagation direction of electromagnetic waves. This innovative alignment effectively disrupts time-reversal symmetry, enabling asymmetric transmission. A thorough analysis of the electromagnetic field distribution and surface current patterns offers insights into the fundamental mechanisms underlying this asymmetric transmission. Notably, the ability of this MM design to maintain the polarization state of transmitted waves positions it as a promising candidate for terahertz systems applications.

The design and application of magnetic landmark used for magnetic fiducialization of HEPS insertion devices*

Abstract Achieving high performance in synchrotron radiation light sources demands increased precision in fiducialization and alignment of insertion devices (IDs). Conventional sensor systems utilizing Hall probes for high-precision magnetic field measurements face limitations in determining the absolute position of the magnetic center of IDs. In this paper, the Magnetic Landmark (MLK), a novel solution based on a magnetized block structure, is designed to address this challenge. The MLK serves as an intermediary, establishing contact between the magnetic center of IDs and their externally accessible fiducials, thus enabling high-precision alignment. Through analysis of magnetic field distribution, self-calibration precision, and practical application of the MLK, the following conclusions are drawn: when the Hall probe is positioned within 0.5 mm of the magnetic field zero point inside the MLK, the measurement accuracy of the zero point for normal and skew quadrupole magnetic fields reaches 7 and 2 μm, respectively. Additionally, the self-measurement accuracy of the MLK is 10 and 4 μm in the transverse and vertical directions, respectively. These accuracies meet our usage requirements. The MLK demonstrates efficacy in aligning the magnetic center of High Energy Photon Source (HEPS) In-air undulators, achieving alignment accuracies of 16 μm in the transverse direction and 11 μm in the vertical direction, surpassing the 30 μm accuracy stipulated in the physical design. Furthermore, the device proves applicable for measuring the magnetic center of other types of HEPS insertion devices, including Cryogenic undulators.

Simulation based comparative analysis of electric field stress on insulated cross-arm

Insulated cross-arms for overhead transmission lines have become increasingly common in the past decade. The 3D finite element analysis (FEA) of the electric field distribution in insulated cross-arms is particularly intriguing due to the differences from conventional glass or ceramic insulators. The complex geometry of composite cross-arms, which feature four separate insulator strings and varying shed profiles, poses a challenge in modelling them using 3D FEA packages. The findings indicate that insulated cross-arms can operate within suitable parameters for traditional composite insulators. This paper presents and analyses the electric field distribution around an insulated cross-arm, which aims to replace existing high-voltage insulators and the steel cross-arms of transmission towers. The design of grading devices plays a crucial role in ensuring the safety of these structures. The use of grading ring devices at both ends of the insulator has proven effective in relieving stress on the insulator string under normal and abnormal conditions, enabling the insulated cross-arm to function effectively with conventional composite insulators. Significant reductions in electric field strength were observed, amounting to approximately 35.93 % inside the core, 31.14 % on the core surface, 35.64 % through the shed, and 16.67 % above the shed for compression members. For tension members, reductions from the low-voltage end to both ends were around 33.82 % inside the core, 38.55 % on the core surface, and 17.48 % through the shed. However, an 8.43 % increase was observed above the shed, indicating a deviation from the decreasing trend observed in other areas. These research findings provide valuable insights for designing and managing high-voltage systems, ensuring effective insulation and enhanced safety. It benefits electrical utilities and transmission line manufacturers by improving reliability and safety for overhead transmission lines.

Threshold Voltage Modulation and Gate Leakage Suppression of Enhancement‐Mode GaN HEMT by Metal/Insulator/p‐GaN Gate Structure

Herein, a metal/insulator/p‐GaN gate HEMT (MIP‐HEMT) with Si3N4 gate dielectric layer is fabricated. Compared to the conventional p‐GaN HEMT, the MIP‐HEMT has a higher threshold voltage (Vth) of 4.8 V and better gate leakage suppression. The mechanism of threshold voltage increase in MIP‐HEMT is elucidated through an analysis of the electric field distribution in the gate region and the proposed gate capacitance model. Furthermore, MIP‐HEMTs with gate dielectric layers of varying dielectric constants and thicknesses are designed and simulated. The obtained results lead to the derivation of an empirical formula for the threshold voltage of the MIP‐HEMT under ideal dielectric/p‐GaN interface conditions, in relation to the dielectric constant and thickness of the gate dielectric layer. Additionally, simulations are conducted on the MIP‐HEMT incorporating fixed charges at the dielectric/p‐GaN interface, and the impact of interface charges is investigated. This refinement enables a more accurate prediction of the MIP‐HEMT's threshold voltage. Conclusively, MIP‐HEMTs can effectively modulate the threshold voltage by manipulating the parameters of the gate dielectric layer, thereby extending the threshold voltage range of conventional enhancement‐mode devices.

Enhanced electromagnetic wave absorption in ultrathin cement-based composites with integrated multi-dimensional carbon materials

The challenges posed by electromagnetic waves (EMW) cause significant interference in electronic device operation, jeopardizing information security and disturbing normal biological functions, which necessitate attention. Multi-scale carbon/cement-based composites were developed for EMW absorption by integrating multi-dimensional carbon materials, including carbon nanotubes (1D), graphene (2D), and modified carbon microspheres (3D). These composites demonstrate exceptional EMW absorption capabilities, with a minimum reflection loss (RLmin) of −44.32 dB and an effective absorption bandwidth (EAB) of 3.644 GHz at X band, merely having a thickness of 1.90 mm. Furthermore, the superior EMW absorption properties of these composites are confirmed through radar cross-section (RCS) simulation and electric field distribution analysis. A small house is constructed of designed three-layer multi-scale carbon/cement-based composites in which the actual EMW reflection losses are less than –10 dB within the whole test frequency range, and these composites can effectively obstruct 5 G mobile phone signals. Therefore, multi-scale carbon/cement-based composites could be promising candidates for effectively solving the increasingly serious problem of electromagnetic radiation pollution.

Giant goos–hanchen shift with heigh reflection base on guided mode resonance in trapezoidal hBN/dielectric metasurface

hBN is a natural hyperbolic van der Waals material that can enhance light–matter interactions. In this work, the maximum Goos-Hanchen(GH) shift has a magnitude of −4680 μm with high reflection using the central beam method in the trapezoidal dielectric/hBN grating (TDG) metasurface (MS) where the beam waist w0≥4λ. Analysis of the electromagnetic field distribution indicated that the amplified GH shift was a result of guided mode resonances excited in the waveguide dielectric layer. The frequency and magnitude of GH shifts can be effectively controlled by adjusting the height of the trapezoidal hBN, as well as by manipulating the widths of the top and bottom dielectric layers, the period of the TDG structure, and the height of the multi-layered structure. Moreover, an evaluation of the structure-sensing properties based on the GH shift was conducted. The enhanced and controllable GH shift exhibited by the TDG MS presents promising prospects for applications in optical sensors, optical switches, and optoelectronic detectors.

Transmission/reflection mode switchable ultra-broadband terahertz vanadium dioxide (VO2) metasurface filter for electromagnetic shielding application

In this paper, we present an ultra-broadband terahertz (THz) vanadium dioxides (VO2) metasurface (MS) filter with switchable transmission/reflection modes for electromagnetic (EM) shielding application. The MS filter is composed of a three-layer periodic composite structure, consisting of two VO2/metallic hybrid layers and a metal mesh layer, which are separated by two benzocyclobutene (BCB) dielectric layers. The transmission property of the proposed MS filter is illustrated by the numerical simulation based on the finite element method (FEM) and equivalent circuit model (ECM). When VO2 is in insulating state, the designed composite structure acts as a filter with ultra-broadband bandpass response (BPR), exhibiting that the transmission coefficient exceeds 90 % from 1.07 THz to 3.78 THz, with a relative bandwidth of 112 %. However, owing to thermal excitation, the VO2 converts from an insulating to a metallic state, the composite structure can be functioned as a filter with ultra-broadband bandstop response (BSR) with a transmission coefficient less than 6 % spanning the range of 0.1 to 4.5 THz. In addition, the physical mechanism of the designed MS filter is investigated utilizing impedance matching theory and electric field distribution analysis. Furthermore, the MS filter has good polarization insensitivity and angular stability. Finally, we quantify the shielding effectiveness (SE) in two states and evaluate the impact structural parameters of the unit-cell, resulting in a SE of more than 25 dB in reflection mode across the entire operating frequency range. Our proposed MS filter with its exquisite performance has the potential to be widely applied in EM shielding.