Abstracts:Terahertz holographic technology, benefiting from the abundant resources, low photon energy, and strong penetration capabilities of terahertz, demonstrates tremendous potential in ultrawideband and high-speed wireless transmission for next-generation communication. However, current terahertz holographic components suffer from limitations such as restricted information capacity and poor communication security, hindering further development and practical application in the telecommunications field. Here, we report a thermally modulated metasurface with controllable far-field radiation characteristics and demonstrate a dual-band holographic encryption device. The structural symmetry of the meta-atom is broken to excite electromagnetic-induced transparent modes and Fano resonance modes with opposite far-field transmission characteristics at 0.34 and 0.42 THz, respectively. Utilizing the phase transition between insulating and metallic states in temperature-responsive vanadium dioxide, the asymmetric parameters of the meta-atom could be altered to achieve resonance modulation, resulting in amplitude enhancement or attenuation. Based on the proposed meta-atom, the controllable 2-bit encoding units could be constructed at 0.34 and 0.42 THz through structural parametric adjustments. Finally, a holographic element featuring 3-D encryption across polarization, temperature, and frequency is demonstrated in simulation with information including “L,” “C,” and “O.” The proposed strategy will advance the development of encrypted information transmission and integrated communication devices.

Abstracts:Coreless winding topologies are a pivotal design element in a diverse range of electromagnetic devices, from high-precision actuators to high-energy pulsed-power systems. These configurations are essential for achieving high power density and rapid dynamic response, with conventional topologies including rectangular, skewed, diamond, and hexagonal. To further reduce material consumption, improve magnetic flux utilization, and enhance electromagnetic performance, this article proposes a novel elliptical winding topology, with a focus on its implementation in coreless brushed permanent magnet dc motors (CBPMDCMs). The structural design of the motor and elliptical winding is first introduced. Detailed analytical models for back EMF, electromagnetic, and mechanical characteristics are then developed and validated through 3-D finite element analysis (3-D FEA). A comparative study is subsequently conducted between the elliptical winding and conventional windings under identical performance requirements. The results demonstrate that the elliptical winding achieves higher flux utilization, lower copper consumption, improved efficiency, and stronger short-term overload capability, while maintaining competitive electromagnetic and mechanical performance.

Abstracts:This article investigates the role of plasma support electromagnetic (EM) interactions and surface plasmon polariton (SPP) in enhancing the performance of terahertz (THz) wireless body area networks (WBANs) for consumer health applications. A bending log-periodic graphene-based antenna is proposed, comprising multiple log-periodic graphene elements excited through a silver nanostrip feedline to support plasmonic wave confinement. The antenna demonstrates dual-band operation at 5.95 and 6.31 THz, where the excitation of SPP modes leads to strong field localization and reduced propagation losses. The antenna exhibits impressive return loss values of −47.71 and −24.27 dB at 5.95 and 6.31 THz, respectively, ensuring minimal signal reflection. The front-to-back ratio (FBR) is 11.12, with an efficiency of 81% and 50.7% the antenna achieves a directivity of 10.14 dBi. It is ensuring reliable performance in plasma-mediated THz propagation. Bending analysis validates structural robustness under realistic WBAN conditions, while a three-layered human body model is employed to assess the specific absorption rate (SAR), confirming low exposure levels suitable for long-term wearable and implantable applications. Further, computer simulation technology (CST), HSS, and ADS results have been verified and validated using mathematical modeling. The integration of plasma-driven SPP mechanisms with graphene antenna technology highlights a pathway toward high-performance THz WBANs, enabling safe and continuous health monitoring through smart textiles and advanced biomedical platforms.

Abstracts:Imperfect electrical contact between two rough conductors is often involved in electromagnetic field analysis, where the contact zone is a very thin domain with complex geometry and is physically modeled as contact resistance. In electromagnetic simulations, contact resistance is usually characterized by a constant-thickness contact layer with the corresponding conductivity. However, since the thickness of the contact layer (tens of micrometers) is much smaller than the sizes of the armature and rail (tens of millimeters), this spatial multiscale phenomenon requires an extremely large number of meshes, making simulations too costly. In this article, the imperfect sliding electrical contact between the rail and armature in railguns is taken as the subject. A boundary condition model is presented, where the contact layer is replaced as a zero-thickness interface with strongly discontinuous interface conditions connecting the surroundings. This model avoids meshing the thin layer and reflects changes in contact pressure and liquid aluminum material in interface conditions. In addition, a general discontinuous Galerkin (DG) framework ensuring the interfacial strong discontinuity is introduced by defining numerical fluxes that follow the discontinuity. This method is precise and guarantees good condition numbers, even in extreme cases of very large or small contact conductivities. To verify the correctness and effectiveness, current density results were calculated using the boundary condition model and the classical contact layer model (CLM) and were found to be consistent; the element number and computation time of the boundary condition model are less than those of the classical model. Furthermore, the effects of imperfect electrical contact on electromagnetic fields were analyzed using the abovementioned methods at velocities of 0, 100, 500, and 1000 m/s.

Abstracts:In this work, the effect of an ac-driven pin-to-pin gliding arc discharge (GAD) on premixed NH3/O2 combustion is experimentally investigated. The discharge substantially improves flame stability and extends the lean flammability limit from $\varphi =0.55$ to 0.30. Meanwhile, an approximately 80% reduction in NO emissions is achieved under plasma-assisted conditions. With increasing oxygen flow rate, the discharge undergoes a transition from glow to spark types, which promotes the ignition of lean mixtures. Optical emission spectroscopy (OES) identifies the presence of OH ${}^{\ast }$ , NH ${}^{\ast }$ , and N ${}_{2}^{\ast } $ species only when plasma participates in burning, while the intensity of NH ${}_{2}^{\ast } $ emission is markedly increased. As the equivalence ratio increases, OH ${}^{\ast }$ emission decreases, whereas NH ${}^{\ast }$ , NH ${}_{2}^{\ast } $ , and N ${}_{2}^{\ast } $ emissions are strengthened, implying enhanced NH3 dissociation induced by the plasma. Based on these results, we propose a set of DeNOx reaction pathways involving plasma-generated NHx radicals.

Abstracts:Accurately and efficiently solving the physical characteristics of electromagnetic railguns is essential for understanding their dynamic behavior and ensuring reliable design. However, an effective real-time solution for the multiphysics coupling characteristics of electromagnetic railguns has yet to be proposed. This article develops a modified set of governing equations for electromagneticthermal coupling based on the arbitrary LagrangianEulerian (ALE) dynamic mesh framework and applies them to the transient electromagnetic launch process. Additionally, a hybrid meshing strategy combining sliding and dynamic meshes is introduced, where sliding meshes are utilized for the armature region and the rail sections in contact with the armature, while dynamic meshes are applied to the remaining rail sections. This approach effectively balances computational accuracy and complexity, enabling precise real-time solutions for the multiphysics characteristics of transient and high-speed models. To validate the proposed method, numerical results from static meshes, single-physics simulations, and the modified multiphysics coupling solution are compared with experimental data. The results demonstrate the effectiveness and efficiency of the proposed approach in achieving accurate and real-time multiphysics simulations of electromagnetic railgun launches.

Abstracts:This article presents the coupling characteristics of shielded multiconductor cables under high-altitude electromagnetic pulse (HEMP) numerically and experimentally. The numerical analysis is employed to study the coupling characteristics of a representative shielded multiconductor cable under different conditions first. The impacts of cable wiring configurations, cable parameters, and propagation direction of incident electromagnetic waves are given. Then, a horizontally polarized hybrid EMP simulator is constructed, and some radiated tests are conducted to validate the conclusions obtained in numerical analysis. The results show that the open circuit of the shielding layer results in the core wire coupling to the same high voltage as the shielding layer, while grounding the shielding layer significantly reduces the coupling voltage on core wires. In addition, increasing cable height, cable length, elevation angle, and azimuth angle all result in an amplification of the level of coupled current. The experimental outcomes of the radiated tests validate the effectiveness of the simulation and the precision of the numerical analysis results.

Abstracts:Neutral beam injection (NBI) is a key auxiliary heating technology used in magnetic confinement fusion devices. With the scale up of the device, the requirement of beam energy is higher. A negative ion source-based neutral beam injection (NNBI) system is an inevitable choice, but the NNBI system presents significant engineering complexity and technical challenges. To investigate and master core NNBI technologies, an NNBI test facility is currently being developed under the Comprehensive Research Facility for Fusion Technology (CRAFT) in China. The initial operational targets for the CRAFT NNBI system are to achieve a beam with energies in the range of 200400 keV, the neutral beam power of 2 MW, and the pulse duration of 100 s. In the negative ion source, the beam divergence is one of the important parameters that determines the pulse duration and energy of the beam. A large beam divergence will cause heavy thermal load on the electrode grids and additional heat load on the beamline components. These can cause the breakdown of grids and interrupt the acceleration process. The accelerator beam optics design for the CRAFT NNBI dual-driver negative ion source is based on IBSimu. Two diagnostic methods, beam emission spectroscopy (BES) and secondary electron emission (SEE), are adopted to analyze the optical characteristics of beam in the experiments. The experimental results verify the simulation results calculated by IBSimu, confirming the limitations and reliability of the simulation program.

Abstracts:The Z-Pinch Initiation Facility (ZIF) was built to investigate the effect of initial conditions (e.g., rate of voltage rise) on the stability of a dense Z-pinch formed from a frozen deuterium fiber. The motivation was work initially performed in 1987 by the Naval Research Laboratory (NRL) and Los Alamos National Laboratory (LANL) that reported stability far longer than predicted by magnetohydrodynamic (MHD) theory. NRL observed stability as long as the current was rising, up to 640 kA and 130 ns. ZIF can drive up to 250 kA in 80 ns through a single 34-cm-long fiber. In some cases, apparent stability was observed based on visible light streak camera photographs and neutron detectors, which replicated the NRL results. However, in all cases on ZIF, the more extensive diagnostics revealed turbulent $m =0$ behavior that dominated the pinch dynamics. Visible light framing images showed short wavelength $m =0$ activity (ka~20) as early as 30 ns after start of the current. Laser shadowgraphy also showed $m =0$ activity. These are consistent with 2-D and 3-D simulations of the experiments. The 2.45-MeV neutrons are produced during the current rise and as much as 120–230 ns after current peak. There are still unresolved differences between the ZIF and previous results, which may be due to differences in the Z-pinch current driver. This is one of four papers on ZIF. Others discuss the ZIF pulsed power, the ZIF diagnostic suite, and simulations. An archive of all results will be made available to the public in 2026.