Electromagnetic Waves Research Articles

Lightweight TiC/ZrC ceramic foams were successfully fabricated using a self-foaming method to address thermal-electromagnetic coupling in extremely high-temperature environments. These ceramic foams feature an interconnected pore structure, achieving a porosity of 75.2% and a density of 0.41 g/cm3. The foam demonstrates low thermal conductivity of 0.21 W·m-1·K-1, promising broadband electromagnetic wave absorption with a minimum reflection loss (RLmin) of -33.9 dB and an effective absorption bandwidth (EAB) of 3.7 GHz. Additionally, it exhibits high load-bearing strength of 26 MPa. The exceptional multifunctionality of these ceramic foams is primarily due to their interconnected pore structure and the solid solution strengthening of TiC in ZrC ceramics. Notably, the ceramic foam also shows remarkable high-temperature resilience. After undergoing five thermal cycles at 1600 °C, the material maintains its structural integrity and performance stability, with electromagnetic absorption characteristics dropped to RLmin of -28.7 dB, along with a mechanical strength of 9 MPa.

During the last seconds of a binary neutron-star merger, the tidal force can excite stellar oscillation modes to large amplitudes. From the perspective of premerger electromagnetic emissions and next-generation gravitational wave (GW) detectors, gravity (g-) modes constitute a propitious class. However, existing estimates for their impact employ linear schemes, which may be inaccurate for large amplitudes, as achieved by tidal resonances. With rotation, inertial modes can be excited as well, and while their nonlinear saturation has been studied, an extension to fully consistent gravito-inertial modes, especially in the neutron-star context, is an open problem. We study linear gravito-inertial modes and the nonlinear saturation of these modes and investigate the astrophysical consequences for binary neutron-star mergers, including the possibility of tidally excited dynamo activity. A new (non)linear formulation based on the separation of equilibrium and dynamical tides is developed. Implementing this into the 3D pseudo-spectral code MagIC a suite of nonlinear simulations of tidally excited flows with an entropy and/or composition gradient in a stably stratified Boussinesq spherical-shell are carried out. The new formulation accurately reproduces results of linear calculations for gravito-inertial modes with a free surface for low frequencies. For a constant-density cavity, we show that the axisymmetric differential rotation induced by nonlinear _2g and _1g modes may theoretically be large enough to amplify an ambient magnetic field to ≳ 10^ G. In addition, rich nonlinear dynamics are observed in the form of parametric instabilities of the _1g mode. The stars are also spun-up, which extends the resonance window for any given mode. This study provides nonlinear numerical support for a recently proposed scenario where, to accommodate the nonthermal precursor flares seen in some short gamma-ray bursts, the magnetic field of a premerger star is amplified by resonant g-modes. It further suggests that g-mode resonances may have a stronger impact on GW signals than previously estimated.

Effects involving interactions between electromagnetic waves and applied electric field in materials, commonly known as electro-optic effects, have remarkably diverse applications ranging from telecommunications to next-generation photonic devices. Identification of materials with large electro-optic response is highly desirable for these applications; however, associated experiments remain challenging. Ab initio simulations provide a convenient avenue for evaluating the strength of electro- and elasto-optic effects in crystals, as well as other related properties. Here, we introduce an efficient workflow for predicting tensorial electro-optic coefficients (Pockels and Kerr) in non-magnetic crystals of most symmetries, including all the necessary ingredients, such as dielectric, elasto-optic, and electrostrictive tensors. This approach can also be utilized for evaluating descriptors in high-throughput evaluations of optical properties. We benchmark our simulations on tetragonal BaTiO3 and wurtzite AlN crystals, obtaining, where available, reasonably good agreement with the results of prior experimental and theoretical reports.

Time reversal techniques have been investigated for ultrasound and electromagnetic waves. They offer some advantages, particularly in cluttered and inhomogeneous environments, for point-to-point applications. The instrumentation usually employed for electromagnetic time reversal involves costly vector network analyzers, different interconnected generators and receivers, or a base station for mobile phones. This article explores the use of a low-cost commercial software-defined radio, in frequencies between 700 MHz and 2100 MHz, with indoor tests showing its performance and observed voltage gains for the received pulse.

Green synthesis is a sustainable alternative to conventional material synthesis methods, minimizing environmental impact, and improving process safety. This study reports the synthesis of cobalt tungstate (CoWO 4 ) via a green synthesis route using natural polymerizing agents derived from plant‐based (agar–agar) and animal‐based (gelatin) sources. Structural characterization is performed by X‐ray diffraction, complemented by Rietveld refinement to obtain precise crystallographic parameters. A microwave filter featuring a Matryoshka‐type fractal geometry is fabricated and utilized for the experimental evaluation of the electromagnetic response of the synthesized samples. Transmission losses are correlated with the crystalline structure of CoWO 4 , with the aim of optimizing the material for microwave‐frequency applications. The results indicate that the stoichiometric composition and crystal structure directly influence the interaction of CoWO 4 with electromagnetic waves, impacting transmission levels and losses at different frequencies.

Abstract Within this study, we delve into novel optical solitons concerning the perturbed nonlinear Schrödinger equation, which governs the propagation of electromagnetic waves in magneto-optic waveguides. These components play vital roles in optical transmission lines and lasers, serving critical functions within integrated optical circuits as circulators, modulators, and isolators. Employing the simplest equation method, the 1 φ ( δ ) , φ ′ ( δ ) φ ( δ ) \left(\phantom{\rule[-0.75em]{}{0ex}},\frac{1}{\varphi \left(\delta )},\frac{\varphi ^{\prime} \left(\delta )}{\varphi \left(\delta )}\right) method, and the generalized Riccati equation mapping method, we derive single and multi-optical soliton solutions. Our analysis yields a diverse array of solutions, including multi-soliton, singular, combo bright-dark, periodic singular, bright, and dark optical solitons. Additionally, we discuss the parametric conditions crucial for both the existence and shaping of these solitons. The visual representation of our findings through three-dimensional, two-dimensional, and contour plots elucidates the dynamic phenomena and interprets the physical implications of these solutions using various parameter values. This research demonstrates the efficacy of rational analytical methods in elucidating the intricate dynamics of soliton solutions in nonlinear optical systems, thereby offering valuable insights for further exploration in the fields of physics, mathematics, sciences, and engineering.

Electromagnetic temporal boundaries, emerging when the constitutive parameters of a medium undergo abrupt temporal variations, have garnered significant interest for their role in facilitating unconventional wave phenomena and enabling sophisticated field manipulations. A key manifestation is temporal reflection in an unbounded spatial domain, where a sudden temporal discontinuity induces phase‐conjugated backward waves alongside anomalous spin conversion. This study explores distinctive spin‐conversion dynamics at a time‐dependent spatial interface governed by Lorentz‐type dispersion, in which the plasma frequency undergoes rapid modulation over time. The interaction of a circularly polarized wave with a space‐time interface excites electromagnetic signals at the system's natural resonance, allowing precise control over polarization states. The scattered field stems from the combined influence of temporal and spatial boundaries, yielding a superposition of the original incident wave's polarization and its phase‐conjugated counterpart.

Abstract Facing increasing absorption requirements for the low‐frequency (2–8 GHz) electromagnetic wave (EMW) energy, dielectric‐magnetic heterojunction design is heading toward a bottleneck. Herein, a unique exposure surface strategy is induced to modulate the dielectric polarization behaviors via the electronic structure manipulation. Multi‐heterointerface Co/MnO/MnO 2 (CMM) architecture with controllably tuned exposed (131) surface is developed to improve low‐frequency EMW absorption performance. Notably, increased exposure of the (131) surface in MnO 2 semiconductors significantly enhances polarization effects, which further optimizes impedance matching and boosts attenuation capability, thereby enabling 2–8 GHz frequency‐tunable absorption. The interface engineering‐mediated exposed surface and heterointerface synergistic strategy enables fundamental regulation of dielectric properties and loss mechanisms. The optimized CMM composite demonstrates a strong EMW absorption capability with a minimum reflection loss of −48.3 dB at 3.92 GHz, the effective absorption bandwidth covering 54% of the 4–8 GHz band. Meanwhile, it exhibits exceptional multifunctionality, including excellent thermal conductivity and enhanced mechanical properties. This breakthrough study provides a novel strategy for controlling interface polarization by exposed surface engineering, paving the way for high‐performance, low‐frequency EMW absorbing materials.

Abstract A particle traversing a crystal aligned with one of its crystallographic axes experiences a strong electromagnetic field that is constant along the direction of motion over macroscopic distances. For "Equation missing" and $$\gamma $$ γ -rays with energies above a few $$\textrm{GeV}$$ GeV , this field is amplified by the Lorentz boost, to the point of exceeding the Schwinger critical field $$\mathcal {E}_0 \sim 1.32 \times 10^{16}~\mathrm {V/cm}$$ E 0 ∼ 1.32 × 10 16 V / cm . In this regime, nonlinear quantum-electrodynamical effects occur, such as the enhancement of intense electromagnetic radiation emission and pair production, so that the electromagnetic shower development is accelerated and the effective shower length is reduced compared to amorphous materials. We have investigated this phenomenon in lead tungstate ( $$\textrm{PbWO}_4$$ PbWO 4 ), a high- Z scintillator widely used in particle detection. We have observed a substantial increase in scintillation light at small incidence angles with respect to the main lattice axes. Measurements with $$120~\textrm{GeV}$$ 120 GeV electrons and $$\gamma $$ γ -rays between 5 and $$100~\textrm{GeV}$$ 100 GeV demonstrate up to a threefold increase in energy deposition in oriented samples. These findings challenge the current models of shower development in crystal scintillators and could guide the development of next-generation accelerator- and space-borne detectors.

Electromagnetic wave propagation algorithm: A novel electromagnetic wave propagation-inspired optimizer for engineering applications

Low-reflection electromagnetic interference shielding composite foams with asymmetric structure towards infrared camouflage and response switching.

Excellent absorption-dominant electromagnetic interference shielding performances of asymmetric gradient layered composite films exploited with assistance of machine learning.

Multifunctional polysulfone composite membranes via constructing electrically conductive gradient and magnetic-core/electric-shell dual-gradient microstructures: A strategy to tackle multiple hazards.

Physical foundations for trustworthy medical imaging: A survey for artificial intelligence researchers.

Hypervelocity impacts (HVI) from micrometeoroids and orbital debris can produce dense plasmas that may interfere with spacecraft electronics via electromagnetic radiation. This work presents a computational framework to characterize plasma formation during the early stages of an HVI event. A solid-state shock model is used to calculate post-shock, pre-ionized thermodynamic properties for iron-on-iron impacts across a range of velocities (6–50 km/s), employing five different equations of state (EOS). These results serve as inputs to a 0D3V Monte Carlo collision model, which simulates the transient ionization of the shocked material. At low impact velocities (<15 km/s), all EOS produce similar results but diverge at higher velocities due to differences in how they capture phase transitions and quantum effects. The system enters a warm dense matter regime in the post-shock, pre-ionized phase, characterized by strongly coupled ions and moderately degenerate electrons. Ionization occurs on the order of femtoseconds, which is much faster than plasma expansion or electromagnetic propagation over an impactor's characteristic length, validating the assumption of instantaneous plasma formation. We find lower impact velocities will produce partially ionized plasmas, while higher impact velocities will produce fully ionized plasmas, with the threshold defining “low” and “high” velocities depending on the EOS used. Overall, this work provides estimates of temperature, density, and ionization levels immediately after impact, offering improved initial conditions for plasma expansion and radiation models. It also underscores the need for more accurate EOS in extreme regimes and lays the groundwork for future integration with experimental validation and electromagnetic diagnostics in the context of spacecraft missions.

Several assumptions at the foundation of the standard cosmological model have as a direct consequence a specific relation between cosmological distances, known as the distance duality relation, whose violation would be a smoking gun of deviations from standard cosmology. We explore the role of upcoming gravitational wave observations in investigating possible deviations from the distance duality relation, alongside the more commonly used supernovae. We find that, when combined with baryon acoustic oscillations, gravitational waves will provide similar constraining power to the combination of baryon acoustic oscillations and supernovae. Moreover, the combination of observables with different sensitivities to electromagnetic and gravitational physics provides a promising way to discriminate among different physical mechanisms that could lead to violations of the distance duality relation.

Decoupled manipulation of electromagnetic and acoustic waves via fully-structural-designed hybrid metamaterials

Multidimensional heterostructure synergistic modulation of carbonyl iron/biomass-derived carbon composites for broadband efficient electromagnetic wave attenuation

Graphene can effectively enhance the impedance matching and dielectric loss capability in dielectric loss/magnetic loss dual-mechanism absorbers, and influences the overall magnetic loss capability of the material through various mechanisms. In this study, carbonyl iron/graphene composite absorbers with different graphene contents were prepared using the solution blending method. An absorbing honeycomb structure was fabricated using aramid honeycomb as the substrate via an impregnation process. The complex permittivity and complex permeability of the materials were tested within the 2–18 GHz frequency band. The absorption capability and mechanism were comprehensively analyzed alongside the reflection loss curves. Furthermore, the influence of graphene on the magnetic loss capability of the dual-mechanism absorbing material was investigated through VSM tests. Research indicates that the content and distribution of graphene can enhance the dispersion of CIP. In addition to a significant improvement in dielectric loss, it also exerts an influence on magnetic loss through a synergistic mechanism.

Enhanced electromagnetic wave absorption of La-doped Ba3Co2Fe24O41 Z-type hexaferrite with wide effective absorption bandwidth