The present study aimed to develop a green and sustainable approach for the synthesis of a TiO2-chitosan nanocomposite using Laggera alata leaf extract and to evaluate its physicochemical characteristics and potential biomedical activities. Preliminary phytochemical screening of the aqueous leaf extract revealed the presence of alkaloids, flavonoids, phenols, tannins, saponins, and carbohydrates, while glycosides, terpenoids, steroids, and proteins were not detected. The synthesized TiO2-chitosan nanocomposite was characterized using UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX). UV-Visible analysis showed an absorption edge around 450 nm, with estimated optical band-gap energy of 1.89 eV. FTIR analysis confirmed the presence of characteristic functional groups associated with chitosan and Ti-O/Ti-O-Ti vibrations, while XRD analysis indicated the crystalline nature of the TiO2 component with an average crystallite size of approximately 23.3 nm. FE-SEM revealed predominantly spherical shape structures with moderate aggregation, while EDX confirmed the elemental composition of the synthesized material. The nanocomposite demonstrated concentration-dependent antioxidant activity in both DPPH and ABTS assays, with IC50 values of 68.98 and 62.78 μg/mL, respectively. Similarly, concentration-dependent inhibition was observed against α-amylase and α-glucosidase, with IC50 values of 156.23 and 254.87 μg/mL, respectively. The nanocomposite also exhibited concentration-dependent cytotoxicity against A431 human epidermoid carcinoma cells, accompanied by morphological alterations and increased apoptotic activity. Overall, the findings demonstrate that L. alata-mediated TiO2-chitosan nanocomposite possesses promising antioxidant, enzyme inhibitory, cytotoxic, and apoptosis-inducing activities. The green synthesis strategy provides a sustainable route for producing a multifunctional nanocomposite; however, further mechanistic, toxicity, and in vivo studies are required to establish its biomedical applicability.
Classical Maxwell–Bloch models are often inadequate for describing electromagnetic wave propagation in complex optical media where memory effects, anomalous relaxation processes, and long-range electromagnetic interactions are important. To address these limitations, this work develops a fractional nonlocal Maxwell–Bloch framework that simultaneously incorporates Caputo fractional temporal memory and nonlocal electromagnetic coupling. The principal novelty lies in the unified treatment of temporal memory and spatial nonlocality within the Maxwell–Bloch framework, together with the corresponding analysis of their effects on optical-wave dynamics. The proposed model captures hereditary polarization dynamics and spatially distributed electromagnetic interactions that are not represented in the standard local integer-order formulation. The analytical part establishes the well-posedness structure of the governing system, including existence, boundedness, and stability properties of solutions in appropriate functional spaces. A spectral stability analysis is further employed to characterize fractional instability thresholds and transitions in the resulting wave propagation. Numerical simulations demonstrate the emergence of localized fractional optical structures, memory-dependent pulse propagation, nonlinear wave interactions, and complex dynamical regimes. A systematic parametric study further shows that variations in the fractional order significantly modify the electric-field profile, energy evolution, and pulse amplitude. The results demonstrate that the combined effects of fractional temporal memory and spatial nonlocality can substantially alter the propagation and stability of electromagnetic waves compared with the classical Maxwell–Bloch limit. The framework therefore provides a unified mathematical and computational basis for investigating memory-dependent and spatially nonlocal optical dynamics.
Atmospheric retrievals of M dwarfs, brown dwarfs, and exoplanets depend on molecular opacities whose quality varies widely across species, and that variation is not yet routinely quantified. This work introduces QORE (Quantum-validated Opacity Retrieval Engine), an opacity-maturity layer that scores each opacity product on five components (provenance, temperature coverage, pressure broadening, completeness, experimental refinement), combines them by a geometric mean, and folds the scored opacities into one forward model. The two least-mature members of a six-species demonstration set are treated with quantum chemistry: for the transition-metal oxides FeO and CrO, absent from standard line-list databases, double-shell CASSCF/NEVPT2 supplies provisional ground-state vibrational anchors (CrO harmonic frequency to 1.8%); for dimethyl sulfide and disulfide (DMS/DMDS) a VPT2 temperature–pressure grid replaces the single-condition cross section in current use. The upgrades raise the maturity of this six-species demonstration set from 0.25 to 0.58, a conclusion insensitive to the component weighting and to one-tier score reassignments. These values grade the selected opacity products only and are not a general quality score for QORE or for any atmospheric retrieval. All production opacities are computed classically; the electronic-structure workflow behind the new products is separately exercised end to end on quantum-computing hardware as a supporting certification, and no quantum advantage is claimed. The scored opacities fit the M8.5–Y4 emission sequence, matching the regime-appropriate Sonora grids in raw fit quality at the coldest objects while trailing them, on raw fit and on information criteria, at the warmer ones, and fit the JWST transmission spectra of K2-18 b and WASP-39 b; in a controlled K2-18 b test within QORE’s simplified transmission branch, the temperature- and pressure-resolved opacity lowers the DMS Bayes factor from lnBF =4.08 to near zero. The score is a heuristic input-quality diagnostic, not a detection statistic or an uncertainty estimate, and the retrieval results are model-conditional.
We begin with a question: Can the curvature of spacetime be the coarse-grained shadow of knotted topology? To answer this question, we develop an effective topological field theory in which the leading scalar-curvature channel of an emergent geometry is sourced not by matter inserted by hand, but by gradients of a knot-density proxy ‘ρ’ built from a continuous unit-vector fibre field. The microscopic substrate is a Faddeev–Skyrme theory whose Hopfion excitations carry an integer Hopf charge ‘Q’, with ‘ρ’ constructed from the topological two-form . Assuming statistical isotropy of the coarse-grained ensemble, we take a conformally flat infrared metric as the leading-order ansatz and impose, as a modelling requirement within this class, that the scalar curvature be linear in □ρ with no independent quadratic-gradient term. This admissibility condition selects the logarithmic factor as the unique simple solution, and yields the weak-gradient relation . The logarithmic form is selected by the geometric admissibility condition within the conformally flat ansatz. It is compatible with dilute-gas microstate counting and large-deviation analysis under their shared dilute-gas factorisation assumption; the latter two supply consistency checks, not independent derivations of the functional form. Crucially, the conformally flat sector has a vanishing Weyl tensor: it recovers only the Poisson-type Ricci-scalar/focusing channel, and a genuine tensor (spin-2) sector remains an open problem. A generalised Raychaudhuri equation carries direction-resolved gradient information and includes a positive Skyrme defocusing term that regularises high-gradient regions while remaining negligible at observable scales. Extending the picture phenomenologically, odd-Q sectors are assigned fermionic Finkelstein–Rubinstein statistics, and a mass functional with three dimensionless shape coefficients of is matched by construction to the electron, muon and tau at Q = 1, 3, 7 — an interpolation, not a prediction. Extrapolating the calibrated functional to Q = 11 and Q = 15 gives heavy-neutral-lepton-like benchmark masses; under a benchmark Type-I seesaw mixing prescription, their suppressed active–sterile mixings imply kilometre-scale decay lengths, placing them beyond currently approved displaced-vertex searches. The result is a mathematically constrained emergent-gravity construction with controlled, falsifiable extensions — and an honest map of what a full unification still has to deliver.
Grain boundaries in polycrystalline Bi2Te3- and Sb2Te3-based thermoelectric materials may strongly modify charge transport through electrostatic band bending and space-charge-layer formation. In this work, surface-potential-controlled intergranular conductance is analyzed theoretically within the framework of classical semiconductor electrostatics and the grain-boundary barrier model. Calculations were performed at T=300K for p-type Bi2Te3 and Sb2Te3 using the dimensionless carrier-imbalance parameters ξ=300, 1000, and 3000 over the surface-potential interval −15≤Ys≤25. Both the absolute conductance variation |ΔG| and the signed conductance variation ΔG were evaluated.For negative surface potentials, ΔG>0 because of hole accumulation near the grain boundary. Moderate positive surface potentials produce ΔG<0, corresponding to majority-carrier depletion. At larger positive Ys, the increasing electron contribution drives ΔG back toward positive values, producing a second zero crossing of the integrated conductance variation. Increasing ξ enhances the accumulation-side response, deepens the depletion minimum, and shifts this second zero crossing from Ys≈13.7 for ξ=300 to Ys≈18.7 for ξ=3000.The dimensionless electrostatic part of the response has the same qualitative form for both materials under identical ξ and mobility-ratio conditions, whereas the dimensional amplitudes differ C=qμpLini2 through the material-dependent prefactor.The calculated values are 1.015×10−5S for Bi2Te3 and 5.297×10−6S for Sb2Te3. Consequently, for the representative parameter sets considered here, the Bi2Te3 conductance response is approximately 1.92 times larger than that of Sb2Te3. The results clarify the separate roles of surface potential, carrier imbalance, and material parameters in grain-boundary-controlled transport. The model is intended to describe qualitative electrostatic trends and does not constitute a direct calculation of the Seebeck coefficient, thermal conductivity, power factor, or thermoelectric figure of merit.
This study investigates the nonlinear dynamics of a double pendulum system with exponentially decaying mass by integrating classical mechanics with fractional calculus to capture memory-dependent chaotic behavior. The primary objectives are: (1) to quantify how time-varying mass amplifies chaos relative to fixed-mass systems, and (2) to establish a fractional-order framework that incorporates non-local effects. Using the Caputo fractional derivative and dimensionless Euler–Lagrange equations, we derive governing equations incorporating mass decay μ(τ) = μ0 e-γτ (γ = 0.1 s-1). Numerical simulations via fourth-order Runge–Kutta and Adams–Bashforth methods reveal that variable mass intensifies nonlinearity, increasing the maximal Lyapunov exponent from 0.1 s-1 (fixed mass) to 0.41 s-1—a 310% rise. Key results include: angular displacements growing by 44.4% (α: 0.18 → 0.26 rad) and 106.7% (β: 0.15 → 0.31 rad); energy fluctuations reaching 10.41 J (vs. 9.82 J for fixed mass) due to asymmetric torque from mass loss; and Poincaré sections confirming chaotic attractors only in the variable-mass case. The fractional-order model reveals that memory effects synergistically amplify chaos, providing more accurate predictions for engineering systems such as adaptive robotics (e.g., arms with shifting payloads) and aerospace vehicles (e.g., fuel-depleting spacecraft), where our model predicts instability thresholds at critical ≈ −0.015 s-1. This work bridges the gap between fractional calculus and real-world variable-mass systems, offering a robust tool for instability prediction and control design.
This study presents designs for both broad- and narrow-bandpass filters intended to operate in the mid-infrared spectrum, specifically in the 3000-5000 nm wavelength range. Silicon was used as the substrate, with thin-film material layers featuring high and low refractive indices. The results demonstrate exceptional optical performance, with transmittance and passbands positioned within the desired wavelength range, meeting various application performance requirements.
This study investigates the steady MHD flow and heat transfer characteristics of a non-Newtonian viscoelastic fluid over a two-dimensional surface. The analysis includes velocity slip, suction or injection effects, solar radiation, and finite-speed heat and mass diffusion modeled using the Cattaneo-Christov framework. The governing PDEs are converted into a system of nonlinear ODEs using appropriate similarity variables and then solved numerically to examine the effects of various physical parameters. The results demonstrate how profiles are influenced by viscoelasticity, velocity slip, thermal radiation, heat stratification, solute stratification, chemical reactions, and Prandtl numbers. The findings indicate that velocity slip and suction reduce the MBL, while viscoelastic effects increase the fluid velocity. Thermal stratification and higher Prandtl numbers decrease thermal diffusion, whereas thermal relaxation and radiation enhance temperature distribution. Stronger chemical reactions and mass relaxation elevate concentration profiles, whereas mass stratification causes them to decline. Furthermore, Nusselt and Sherwood numbers increase with greater thermal radiation, heat generation, chemical reactions, and mass diffusion, while skin friction diminishes with increased slip effects. These insights are useful for thermal and industrial engineering applications involving the control of momentum and heat transfer in non-Newtonian fluid systems.
A theoretical and numerical analysis of a Bell-type experiment is presented, where linear polarization measurements on nonmaximally entangled two-qubit states are modeled through a sigmoid-based threshold mechanism that violates the fair-sampling assumption required by the CHSH inequality. Numerical simulations characterize how closely this local construction can reproduce quantum-like correlations in the postselected detected sample, for both the |Φr〉 and |Ψr〉 states over a range of entanglement parameters. For the tested configurations, the model produces CHSH-type violations only in the postselected detected sample through a setting-dependent detection mechanism, operating outside the assumptions of both the CHSH inequality and Mermin’s 82.8% efficiency bound. The model is not in conflict with loophole-free Bell experiments, which specifically close the detection loophole exploited here. The CH–Eberhard analysis in the one-detector-per-side configuration yields J<0 throughout the full range of entanglement parameters, as required for a strictly local model. The model is further extended with a local adaptive-threshold mechanism implementing one-sided memory. A paired comparison shows that this specific memory rule produces a systematic and reproducible shift in the CH–Eberhard parameter J relative to the fixed-threshold model, while leaving the CH–Eberhard analysis qualitatively unchanged under the tested conditions. The results characterize how a local, setting-dependent postselection mechanism shapes Bell-test statistics across a range of entanglement parameters, within the specific configurations and threshold rules tested.
The present study addresses the effects of thermal radiation and viscous dissipation on climate change in the presence of hybrid nanoparticle fluid flow around a hemisphere fixed at an angle α to the horizontal. The main aim of this study is to investigate climate change sustainability by considering Al2O3–Cu hybrid nanoparticles in the atmosphere as a cooling process. For this purpose, a mathematical model based on nonlinear coupled partial differential equations is formulated, transformed into primitive form using suitable scaling variables, and solved numerically using the finite difference method. Furthermore, the influence of the governing parameters on the velocity, temperature, concentration, skin friction, and mass transfer rate along the hemispherical surface is investigated. The results demonstrate that increasing radiative heat flux reduces fluid velocity due to enhanced thermal radiation effects, while increasing the temperature and mass concentration by promoting thermal energy transport. Moreover, viscous dissipation enhances velocity and temperature profiles through internal heat generation, whereas it decreases the mass concentration due to increased thermal diffusion. The findings provide new insights into the influence of thermal radiation and viscous dissipation on atmospheric heat and mass transport in the presence of hybrid nanoparticles, highlighting their potential for climate-related thermal management applications. The results are presented and discussed using graphs, tables, and contour plots to highlight the physical behaviour of the flow.
Understanding energy dynamics across physical systems requires principles that extend beyond equilibrium and Lagrangian formulations. However, a general symmetry-based description of energy behavior that remains valid without invoking an action principle is still lacking. Here we show that energy dynamics can be formulated in terms of invariant symmetry structures acting directly on energy composition and exchange. By analyzing these structure-preserving transformations, we identify stable energy symmetries whose restriction or breaking gives rise to familiar laws such as classical mechanics and thermodynamics. The framework is developed independently of any specific thermodynamic theory; dynamic/non-dynamic decompositions, including GEB-type formulations and structurally motivated thermodynamic viewpoints, are used only as representative realizations. This approach provides a unified perspective on equilibrium, non-equilibrium, and complex systems, and is supported by both conceptual arguments and numerical tests in driven dissipative scenarios.
The present research investigates numerical solutions of the flow of pseudoplastic trihybrid nanofluid (PTHNF) thin-film subjected to various conditions such as viscous dissipation, non-linear momentum dissipation (Darcy-Forchheimer), and thermal radiation, as well as the impact of magnetohydrodynamics (MHD), chemical reactions, and heat source/sink and Joule heating on the same flow. THNF model consists of three different types of nanoparticles, which are titanium oxide (TiO2), silver (Ag), and copper (Cu), while sodium alginate acts as the base fluid. The effects of heat source/sink and Joule heating on the temperature distribution are noteworthy since high values of thermal conductivity enhance the thermal properties. By applying similarity transformations to the derived rheological system of Partial Differential Equations (PDEs), we arrive at a system of nonlinear Ordinary Differential Equations (ODEs), which we can then solve using the well-known (RK-4) method through MATLAB software. The study graphically discusses and illustrates the rheological effects of the power-law index, solid volume fraction, film thickness, Eckert number, and Prandtl number on momentum, thermal and concentrations fields. For the titanium oxide nanoparticle, the local sensitivity analysis reveals that the Sherwood number is the most sensitive response, followed by the Nusselt number and the skin-friction coefficient, while the wall velocity gradient is the least sensitive. For the silver nanoparticle, the sensitivity analysis identifies the Sherwood number as the most influential response, followed by the Nusselt number and the skin-friction coefficient, while the wall velocity gradient remains the least sensitive among the considered physical quantities.
In this study, we investigate the solitary wave profiles of the Konopelchenko–Dubrovsky equation with the truncated M-fractional derivative. We employed the specific wave transformation to transform the studied partial differential equation (PDE) into a nonlinear ordinary differential equation (ODE), and then using the generalized Riccati equation mapping method to obtain various solitary wave profiles such as dark breather waves, bright breather waves, periodically oscillating waves, kink waves, etc., which are demonstrated graphically by two-dimensional (2D), three-dimensional (3D), and contour diagrams. The memory or hereditary effect in the model is discussed by varying the fractional derivative parameter. Moreover, we also discuss the stability, multistability, and sensitivity analysis of this model. All graphical illustrations are created using MATLAB and Maple. The observed solitary wave profiles demonstrate that this study is novel, reliable, simple, and could be applied straightforwardly across many scientific disciplines to understand the underlying complex wave interactions.
This study investigates the quasi-static mechanical behaviour of shafts composed of saturated porous materials under angular velocity. The porosity is assumed to be uniform, and the structure is considered to be undrained. Biot's constitutive equations were employed to establish the relationship between stresses and strains. Based on the first-order shear deformation theory (FSDT) and the principle of virtual work, the governing equations of the problem were derived. An analytical solution of the equations was obtained using the eigenvalue and eigenvector method under clamped-clamped boundary conditions. The influence of different parameters such as the porosity coefficient, Skempton's coefficient, and angular velocity on the mechanical behaviour of the shafts was examined. The results indicate that both the porosity coefficient and angular velocity significantly influence the mechanical behaviour of the shafts. It was also observed that the axial stress increase with an increase in Skempton's coefficient. Skempton's coefficient has a negligible effect on the displacements and on the radial, circumferential, and shear stresses.
Perovskite materials containing lead halides demonstrate remarkable potential for optoelectronic devices due to their superior efficiency in converting light to electricity while maintaining affordability during manufacturing. However, challenges related to large-scale production, long-term stability, and comprehensive material characterization require further investigation. This work examines thermal processing strategies for fabricating formamidinium lead iodide FAPbI3 solar light absorbers, focusing on methods that balance efficiency with practical scalability. We compare photovoltaic devices manufactured under different conditions and observe similar performance outcomes. Through systematic analysis combining crystallographic measurements obtained during thermal treatment with electrical performance data, we investigate how FAPbI3 processing variables influence device characteristics. Results demonstrate that traditional five-minute heat treatment at 200 °C may be substantially shortened to merely thirty seconds at identical temperature while preserving photovoltaic output. This discovery presents an improved manufacturing pathway for FAPbI3, offering advantages for commercial-scale production and economic viability of perovskite-based photovoltaic technology.
This study investigates the magneto hydrodynamic (MHD) boundary layer flow and double-diffusive heat and mass transfer characteristics of a hybrid nanofluid composed of silver (Ag) and magnesium oxide (MgO) nanoparticles dispersed in water over a vertically oriented cone with convective surface heating. The novelty of the work lies in the simultaneous incorporation of Cattaneo–Christov heat and mass flux theories to model non-Fourier heat conduction and non-Fickian mass diffusion in the presence of hybrid nanofluid effects, space-dependent internal heat generation/absorption, and first-order chemical reaction. A uniform transverse magnetic field is applied to examine electromagnetic control of the transport processes. The governing nonlinear partial differential equations describing continuity, momentum, energy, and concentration are transformed into a coupled system of nonlinear ordinary differential equations using suitable similarity transformations. The resulting system is solved analytically through the Optimal Homotopy Asymptotic Method (OHAM). The results demonstrate that increasing the magnetic parameter significantly suppresses the velocity field due to the enhanced Lorentz force, while simultaneously elevating the temperature distribution because of resistive heating effects. The inclusion of Ag–MgO hybrid nanoparticles substantially enhances thermal performance, yielding nearly 31.2% improvements in heat transfer rate compared with the base fluid. Furthermore, thermal and solutal relaxation parameters delay heat and mass diffusion, thereby reducing thermal and concentration boundary layer thicknesses. Stronger chemical reaction effects markedly decrease concentration profiles through accelerated species consumption. These findings highlight the potential of hybrid nanofluids in advanced cooling technologies, nuclear energy systems, and high-performance thermal management applications.
We propose a minimal-change protocol for engineering multi-qubit quantum states with controllable properties. Starting from a fixed computational-basis input state, the protocol allows controlled variation of state cardinality while evaluating multipartite correlations via standard entanglement measures. Using Hadamard, Pauli-X, and CNOT gates, we separate cardinality expansion from correlation redistribution. Hadamard gates determine wavefunction support size, and CNOTs distribute correlations without increasing occupied basis states. State cardinality serves as a structural descriptor rather than an entanglement classifier. A five-qubit case study shows systematic expansion from low-cardinality superpositions to larger supports while maintaining strong multipartite entanglement. Fidelity and global entanglement analyses indicate that fidelity reductions are due to intentional state reconfiguration, not a loss of correlations, and the framework extends to arbitrary N-qubit systems with favorable resource scaling.
Harmonic suppression in permanent magnet magnetic resonance imaging (MRI) passive shimming is essential to avoid significant degradation of homogeneity caused by uncorrected harmonic fields, which directly compromises image quality and spatial accuracy. However, traditional passive shimming methods, though capable of partially canceling impurity harmonics, struggle with higher-order harmonic components and fail to simultaneously satisfy the dual objectives of harmonic suppression and improved field homogeneity. In addition, shim thickness in permanent magnet MRI shimming must be constrained to accommodate spatial limitations of the magnet gap while simultaneously achieving material efficiency and system lightweighting. To address these limitations, this paper proposes a harmonic passive shimming method with target magnetic field constraint (HPS-TMFC), which integrates target field constraints into the harmonic optimization model to establish a constraint framework encompassing maximum shim thickness limits, magnetic field inhomogeneity boundaries, and targeted harmonic suppression—thus enhancing control over field uniformity and high-order harmonics. Results demonstrate that the HPS-TMFC achieved a field inhomogeneity of 42.1 ppm (While the initial field inhomogeneity before homogenization is 4367.214 ppm)—representing an approximately 50% improvement over the harmonic method and a 13% enhancement compared to the field method. The above results indicate that the method proposed in this paper can effectively suppress harmonic components while significantly reducing magnetic field non-uniformity, and reduce the consumption of shims.
Background Recent advances elaborate the combining magnetohydrodynamics (MHD) with Cross fluid dynamics presents an innovative range of research that mixtures the non-Newtonian performance of multifaceted fluids with the electromagnetic regulator of fluid flow. This pairing has significant inferences in industries, biomedical, and engineering uses. Furthermore, the non-Newtonian fluids have multiplied considerable importance among scientists because of their noteworthy realism in engineering, biological and technical tools. Additional and further uses of exhausting non-Newtonian fluids are actually established in the current domain, counting slurries, fissile devices, creams, melted polymers, and tissues. Transportation tools elaborate in these flow situations, specifically for precise viscous non-linear fluids, are fetching extra significance to recognize as project necessities acquire additional stringent. Objective The current study examines the heat transfer via heat sink/source in chemical reactive Cross fluid with magneto stagnation point flow with stretching surface. A Cross fluid depends on shear rate and is generalized Newtonian in nature. The fluid exhibits electrical conductivity when a magnetic fluid is applied. The governing Partial differential equations (PDEs) are converted into Ordinary differential equations (ODEs) by exhausting similarity changes. Methods Numerical algorithms exist for these modified equations that are determined by using Bvp4c technique. Analysis is conducted on various parameters on temperature, velocity and concentration profiles. Results The results regarding velocity, temperature and concentration are examined using graphs. Results indicate the velocity decays for magnetic number, whereas intensifies for Weissenberg number. The Prandtl factor diminishes the temperature field. The chemical reaction factor enhances and Lewis number decreases the concentration field.
This paper presents a novel dual-resonance ultra-wideband (UWB) circularly polarized (CP) metasurface-loaded ring antenna, exhibiting |S11|<−10 dB over 2.1–2.78 GHz and 3.9–10 GHz (combined FBW ≈130%, compliant with FCC Part 15.517 UWB definition), with asymmetric slot perturbation and an electromagnetic bandgap (EBG) ground for enhanced gain in 5G and satellite communication systems. The antenna is fabricated on an RT/duroid 5880 substrate with relative permittivity ɛr=2.2, loss tangent tanδ=0.0009, thickness h=1.6mm, and overall dimensions of 40×40mm2. A 5 × 5 frequency selective surface (FSS)/metasurface grid is employed to improve impedance matching and radiation characteristics. The axial ratio (AR) remains below 3 dB over two distinct circular polarization (CP) bands, 3.5–4.8 GHz and 6.4–8.3 GHz, providing stable dual-band RHCP operation. Outside these frequency ranges, the AR increases beyond 3 dB and the polarization gradually transitions toward elliptical and linear states; hence, the CP behavior is explicitly characterized as dual-band rather than ultra-wideband. In this context, the term UWB refers to the impedance bandwidth, where |S11|<−10 dB is achieved over 2.1–2.78 GHz and 3.9–10 GHz, resulting in a combined fractional bandwidth of approximately 130%, consistent with FCC Part 15.517. With the inclusion of the EBG ground plane, the antenna achieves a peak realized gain of 12.5 dBi. The asymmetric slot perturbations of 0.8 mm and 0.6 mm effectively excite orthogonal resonant modes, thereby enhancing circular polarization purity within the two AR bands. Furthermore, the metasurface layer suppresses surface-wave propagation, resulting in an average front-to-back ratio (FBR) exceeding 25 dB and a peak FBR of approximately 30 dB at 8 GHz, while maintaining radiation efficiency greater than 85%. The broadside radiation patterns exhibit cross-polarization levels below −20 dB across the useful impedance bandwidth. Owing to its compact configuration and favorable bandwidth–gain trade-off, the proposed antenna outperforms conventional CP ring antennas and is well suited for sub-6 GHz 5G systems, low-Earth-orbit (LEO) satellite communication links, and radar applications.
