Search Results (651)

Infrared cameras used in radio telescopes often suffer image degradation in complex optical and thermal environments. Solar radiation, convergent reflected light, and thermal emission from support structures can substantially impair imaging performance. To address this problem, this paper proposes a split reflective ellipsoidal baffle for suppressing infrared imaging degradation. Unlike conventional baffles, which mainly rely on structural occlusion and surface absorption, the proposed design functions as an upstream stray light regulation unit. It also establishes a computational framework integrating ellipsoidal vane geometry, realistic edge microtopography modelling, ray-tracing simulation, and detector plane irradiance response analysis. First, the reflective properties of the ellipsoidal surface are used to construct an off-axis stray light propagation constraint model. Under this model, incident stray radiation is redirected away from the effective imaging path or guided into light-trapping regions between adjacent vanes. Second, a laser confocal microscope is used to capture the true three-dimensional edge morphology of vanes with different materials and machining angles. This strategy addresses the limitations of the conventional 0.02 mm rounded edge approximation, which cannot accurately represent real scattering behaviour. The measured morphologies are then converted into high-fidelity computational models compatible with ray-tracing analysis. Furthermore, stray light suppression performance is evaluated using point source transmittance, detector plane irradiance distribution, and grey scale response in experimental images. Simulation and darkroom experiments show that the proposed baffle suppresses residual stray light more effectively than conventional absorptive baffles. The results demonstrate a computable, manufacturable, and experimentally verifiable strategy for front-end stray light control and baffle optimisation. This strategy can also support image quality enhancement in infrared imaging systems operating under complex optical and thermal environments. Full article

Polarimetric synthetic aperture radar (Pol-SAR) is one of the most important approaches for sea-surface target detection, but under rainfall conditions it tends to be distorted by the electromagnetic (EM) propagation effects and clutter interference of rainfall. To address this problem, this paper proposes a joint compensation method to mitigate the impacts of rainfall on the detection of sea-surface targets. In the method, a composite imaging model that thoroughly takes into account the propagation and scattering effects of rainfall, sea surface, and ship targets is first established. Then, a range-wise algorithm is proposed to effectively estimate the propagation effects, which are used to compensate for the radar echoes distorted by rainfall. Consequently, a hierarchical search strategy is employed to optimize the receiving polarization state to better discriminate the targets from rainfall and sea clutter. Simulation results show that, across the tested sea-surface wind and rainfall conditions, the proposed method improves the signal-to-clutter-plus-noise ratio (SCNR) by 4 to 13 dB compared with the polarimetric whitening filter, demonstrating its effectiveness under coupled rain–sea conditions. Full article

We present a novel algorithm for the retrieval of non-spherical particle microphysical parameters (PMP) from 3β + 2α + 3δ optical data taken with multiwavelength lidar. The 3β + 2α + 3δ optical datasets describe particle backscatter coefficients (β) at three wavelengths, λ = 355, 532, and 1064 nm, particle extinction coefficients (α) at two wavelengths, λ = 355 and 532 nm, and particle linear depolarization ratios (PLDR, δ) at three wavelengths, λ = 355, 532, and 1064 nm. The algorithm can be used for retrieving bimodal particle size distributions (PSDs). The PSDs can comprise mixtures of spheres and spheroids (SS). One or both modes can comprise spheroid-shaped particles or spherically shaped particles. The spheroids are used for approximating an arbitrary ensemble of non-spherical particles. The algorithm works on the basis of a combination of direct and analytical inversion methods. The algorithm uses the spheroid reference look-up table (RLUT) we developed and presented in part 1 of our research work. The algorithm uses constraints regarding the particle complex refractive index (CRI) and information on relative humidity (RH) in the atmosphere (in the case of aerosol lidar observation) for suppressing retrieval uncertainties. We carried out a numerical simulation study to evaluate the algorithm’s performance. In these numerical simulations, we considered perturbed synthetic 3β + 2α + 3δ optical data that mimic different organic carbon (OC)–dust (D) mixtures. Such mixtures are suitable examples for describing bimodal PSDs that consist of a fine mode of spherical particles and a coarse mode of non-spherical particles. The results of the numerical simulation show that (1) the PMPs of each mode of these particle mixtures can be found separately, (2) the mean retrieval errors of the effective radius, number, surface-area, and volume concentrations of these mixtures are 25%, 52%, 9%, and 28%, respectively, and (3) the mean retrieval error of single-scattering albedo (SSA) at 355 nm of these mixtures is as low as ±0.02. SSA retrieval accuracies at 532 and 1064 nm degrade because the complex refractive index (CRI) of OC and D particles depends on the measurement wavelength. In future studies, we will upgrade the algorithm such that it takes into account a spectrally dependent CRI. We also compare the results of our novel algorithm with our TiARA2.1 algorithm. The errors obtained from the TiARA2.1 algorithm are approximately three times larger compared to the errors we obtain with our novel ATLAS algorithm for the case of the OC-D mixtures considered in the present study. We explain the higher accuracy of the PMP retrievals by the use of three PLDRs and the extra constraints placed on CRI and RH. Full article

The objective of this paper is to introduce the application of quantum annealing (QA) to electromagnetic (EM) engineering. We demonstrate that numerous EM design and inverse problems naturally admit a mathematical formulation in terms of binary quadratic interactions. By utilizing didactic, simplified examples, we illustrate how this underlying physical structure allows for a direct mapping of EM problems onto Quadratic Unconstrained Binary Optimization (QUBO) models and equivalent Ising Hamiltonians. All numerical experiments are conducted using Simulated Annealing as a classical proxy, since the primary contribution of this work is the QUBO formulation itself rather than its execution on quantum hardware. Our results suggest that a broad class of EM problems—including array thinning, reconfigurable intelligent surface optimization, subarray partitioning, and electromagnetic inverse scattering—are suitable candidates for optimization using near-future quantum annealing architectures, once hardware connectivity and noise floors reach the required specifications. Full article

To investigate the slope stability of the north bank anchorage of the Yellow River Three Gorges Bridge during foundation pit excavation and operational stages, a true three-dimensional geological model was established using Rhino6 and numerical simulations were performed using FLAC3D7.0, supplemented by stereographic projection kinematic analysis and the shear strength reduction (SSR) method. Systematic simulations were conducted for foundation pit excavation, main cable load application, heavy rainfall, and two seismic loading conditions, and the deformation characteristics and plastic zone evolution patterns of the slope under different conditions were analyzed. The stereographic projection kinematic analysis indicates that the dominant discontinuity sets do not constitute kinematically admissible planar sliding, wedge sliding, or toppling failure modes, confirming the validity of adopting a continuum model. The numerical simulation results show that the maximum slope displacement after foundation pit excavation is 13.13 mm, with the plastic zone exhibiting a discontinuous scattered distribution, and the slope is overall stable. After the application of the main cable load, the maximum displacement decreases to 7.86 mm; the counterweight effect of the anchorage self-weight significantly improves the deep stability, while the horizontal cable force generates a wedge-shaped shear plastic zone at the slope toe. Under heavy rainfall conditions, rock mass saturation leads to an increase in the maximum displacement to 11.76 mm with expanded plastic zone volume, where the deterioration of strength parameters and the increase in pore water pressure are the primary causes of reduced stability. Under seismic conditions, the maximum displacements under the natural and artificial seismic waves are 15.83 mm and 17.29 mm, respectively, exhibiting a significant elevation amplification effect with extensive plastic zone development in the shallow surface layer. The shear strength reduction analysis yields factors of safety of 2.4 and 2.27 for the heavy rainfall and seismic conditions, respectively, both significantly exceeding the code requirements, demonstrating that the slope possesses an adequate safety margin under extreme loading conditions. Full article

Exhaled breath analysis offers a non-invasive route for metabolic monitoring and disease screening, but its practical implementation requires sensing platforms that combine high sensitivity, robustness, and simplicity. Here, we report an evanescent wave-excited fiber-optic surface-enhanced Raman scattering (SERS) sensor based on silver nanocubes (Ag NCs) assembled onto a fiber taper waist (FTW), and the design is further extended to an Ag/graphene oxide (GO) hybrid interface for enhanced gas detection. Finite element and finite-difference time-domain simulations were employed to optimize the FTW geometry and Ag NC dimensions for efficient evanescent-field excitation and plasmonic enhancement. The fabricated FTW-SERS probe achieved a minimum detectable concentration of 10⁻⁹ M for crystal violet, together with good linearity and a relative standard deviation below 5%. For gas sensing, ethanol and acetone vapors were detected down to 50 ppm using the Ag NC-based FTW-SERS probe. After introducing a 0.3 mg/mL GO functional layer, the minimum detectable concentrations of both analytes were further reduced to 25 ppm. In addition, proof-of-concept monitoring of exhaled ethanol after alcohol consumption revealed dynamic spectral changes consistent with ethanol metabolism. These results demonstrate the potential of evanescent wave-excited FTW-SERS probes for compact and sensitive breath-analysis applications. Full article

We explore the interaction of a plane electromagnetic wave with a topological insulator (TI) cylinder that is coated with homogeneous magnetized ferrite. TIs display exotic electromagnetic responses due to topological magnetoelectric (TME) phenomena. An analytic theory for the electromagnetic scattering from a TI scatterer is developed. The analytical expressions of the polarized electromagnetic fields for the transverse magnetic (TM) case are formulated. The so-called unknown scattering coefficients are derived by implementing the boundary conditions (BCs) on the surface of a TI. The scattering characteristics of plane waves by a TI scatterer are numerically simulated and discussed. The numerical results demonstrate that the scattering characteristics are strongly influenced by the external magnetic field, axion angle, thickness of coating layer, and incident operating wave frequency. This work could provide valuable theoretical insights into the scattering phenomena of optical waves and find promising applications in optical manipulation, particle radiation force and torque, optical diagnosis, metamaterial structures, and wave optics in random media. Full article

Developing eco-friendly metal oxide nanoparticles (NPs) with plant-based reducing and stabilizing agents offers a sustainable alternative to traditional chemical methods. Nonetheless, the detailed mechanisms by which phytochemicals influence NPs formation, antimicrobial properties, and cytocompatibility remain poorly understood, especially in systems mediated by Vaccinium. This study aimed to synthesize TiO₂ NPs and ZnO NPs using Vaccinium corymbosum (blueberry) extract, analyze their structural and surface characteristics, assess their antimicrobial effectiveness and cytotoxicity, and explore potential molecular mechanisms through computational docking. ZnO NPs were produced via alkaline precipitation (pH 12) from ZnCl₂, while food-grade TiO₂ was mixed with blueberry extract. A comprehensive characterization was carried out using techniques like X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission and scanning electron microscopy (TEM/SEM), dynamic light scattering (DLS), and high-performance liquid chromatography (HPLC) for polyphenol profiling. The antimicrobial activity was tested against Escherichia coli and Salmonella Typhimurium, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. Cytotoxicity was assessed using Gallus gallus domesticus leukocytes and Artemia salina bioassays, and molecular docking simulations were performed to examine polyphenol interactions with the bacterial DNA gyrase subunit B (GyrB). XRD analysis confirmed the presence of wurtzite ZnO (with a crystallite size of 18.2 nm) and anatase TiO₂ (12.8 nm after functionalization). HPLC identified key polyphenols, including quercetin, cyanidin, malvidin, and cyanidin-3-glucoside, with patterns indicating stronger adsorption onto TiO₂ NPs surfaces. ZnO NPs showed higher antimicrobial effectiveness (>90% inhibition at 2 mg/mL; MIC 0.5–1 mg/mL) compared to TiO₂ (72% inhibition at 16 mg/mL; MIC 8–16 mg/mL). Cytotoxicity results indicated concentration-dependent effects. Molecular docking simulations revealed favorable binding energies (−6.2 to −8.4 kcal/mol) for blueberry polyphenols with GyrB, suggesting potential synergistic antimicrobial effects and ROS production. The study highlights a successful green synthesis of bioactive TiO₂ NPs and ZnO NPs using Vaccinium corymbosum extract, where polyphenol surface functionalization enhances both colloidal stability and biological activity. This comparative research offers mechanistic insights into how polyphenol-coated NPs work and supports the development of eco-friendly antimicrobial oxide nanomaterials. Full article

LiDAR-based 3D object detection is critical for autonomous driving perception. Ensuring robust sensing under adverse weather is essential for safe deployment. Current physics-based simulation methods focus on atmospheric effects but offer limited ground-level modeling, leading to domain gaps between simulated and real-world snowy data. Ground-level effects are challenging to model due to diverse physical interactions: wet surface reflectivity changes, vehicle-induced spray, and multi-layer snow scattering. This paper proposes a simulation method with more comprehensive ground-effect modeling for snowfall scenarios. Our approach introduces two modules: (i) an extended spray model with precipitation-controlled parameters that jointly models spray noise and wet ground attenuation, and (ii) a multi-layer dual-mode backscattering model that captures both diffuse and specular reflections on snow-covered ground. Both modules share a unified precipitation-driven parameterization. Higher snowfall rates simultaneously control spray generation, wet surface reflectivity, and snow accumulation depth. This design ensures physical consistency and makes the approach applicable across diverse LiDAR systems without sensor-specific tuning. Experiments on the STF dataset demonstrate consistent improvements over four state-of-the-art methods under both heavy and light snowfall. Clear-weather performance is preserved. Evaluations on roadside LiDAR further confirm generalizability to infrastructure-based scenarios. Full article

Poly(amidoamine) (PAMAM) dendrimers are widely recognized as versatile nanocarriers due to their tunable architecture and ability to associate with bioactive molecules. In this study, generation 3 PAMAM dendrimers functionalized with triphenylphosphonium (TPP) were employed to investigate the association of structurally related phenolic compounds—caffeic acid, p-coumaric acid, and cinnamic acid—through either covalent conjugation or non-covalent encapsulation. Physicochemical characterization by NMR, dynamic light scattering, and zeta potential measurements revealed the formation of supramolecular aggregates rather than isolated dendrimer units, with hydrodynamic diameters ranging from 127 to 260 nm and positive surface charge across all formulations. Encapsulation efficiencies determined by HPLC reached 93.8% for caffeic acid, 78.9% for p-coumaric acid, and 71% for cinnamic acid, indicating differential association behavior. Molecular dynamics simulations over 1 μs supported these findings, showing stronger and more stable interactions for polar antioxidants, particularly caffeic acid, driven by hydrogen bonding and electrostatic interactions, while cinnamic acid displayed preferential binding in more hydrophobic dendrimer regions. Radical scavenging assays (DPPH• and ABTS•+) demonstrated that all formulations retained antioxidant capacity, although dendrimer association modulated scavenging kinetics. In cellular assays under oxidative stress, free caffeic acid exhibited the strongest immediate reduction of intracellular reactive oxygen species, whereas dendrimer-associated systems showed reduced but significant activity, consistent with decreased solvent accessibility and slower release predicted by simulations. Overall, these results highlight a trade-off between molecular retention and immediate biological efficacy, demonstrating that the mode of association governs antioxidant accessibility and performance. This combined experimental and computational approach provides a mechanistic framework for the rational design of dendrimer-based delivery systems aimed at balancing stability and functional activity. Full article

The simulation of synthetic aperture radar (SAR) echo signals usually relies on complex hardware equipment and a large amount of scene data, which results in high costs and low efficiency. In order to simulate SAR echo signals of ship targets in the sea quickly and accurately in complex environments at a lower cost, this paper proposes a SAR echo simulation method based on model segmentation and electromagnetic scattering characteristic simulation. This method first implements the simulation of sea models under different sea conditions based on PM wave spectrum model and the Monte Carlo method, and segments them according to the requirements of simulation resolution. Then, it uses Python API 3.11 in Blender 4.5 to segment the ship model automatically and optimize the visible surface elements and mesh for each sub-model. Next, it uses Lua API in Feko to simulate the electromagnetic scattering characteristics of each sub-model of the sea and the ship target automatically, and obtains the required radar cross section (RCS) data of the ship target in the sea after processing. Finally, SAR echo simulation is realized through dual-channel technology. To further verify the simulation result, the chirp scaling (CS) algorithm is used for imaging processing. The results show that this method can realize SAR echo simulation of various ship targets under different sea conditions in a quick, accurate and cost-effective manner without the need for any hardware equipment. Full article

As a rigorous and comprehensive foundation for electromagnetic information theory (EIT), we develop a general theory that elucidates the universal stochastic structure of radiated electromagnetic (EM) fields and induced currents in generic EM information transmission systems. The framework encompasses arbitrary random scatterers, input information fields, and EM mutual coupling. The system is modeled as a multiply connected, arbitrary Riemannian manifold within the language of differential geometry. Our approach exploits exact Green’s functions (GFs) on manifolds to construct a novel electromagnetic random field theory (EM-RFT). Interpreted as response functions localized on the surfaces of transceivers and scatterers, the GFs allow us to treat the internal physical details of the EM system as a black box, redirecting analytical attention toward external input–output relations in line with signal processing and communication theory. This integration of random fields (RFs), electromagnetics, and GFs yields a unified framework for deriving and characterizing the stochastic structure of arbitrary EM information transmission systems. We rigorously establish that EM random fields satisfying Maxwell’s equations can always be constructed using system GFs driven by external information fields. The theory further decouples stochastic input RFs from random fluctuations associated with the communication medium (e.g., scatterers), and introduces general correlation propagators valid for arbitrary EM links. Using the Karhunen–Loève expansion, all EM random fields are represented as sums of random variables, providing both a simulation framework for arbitrary EM RFs and a basis for evaluating mutual information between input and output spatial domains at arbitrary locations in the system. Full article

Dielectric and magnetic spherical hollow shells are employed in many applications as standard building units. These structures are commonly subjected to size reduction to obtain a high surface area/volume ratio, a property that is in favor of specific applications. However, the size reduction enhances the importance of physical mechanisms that originate from surfaces, such as the depolarization effect. Here we tackle the problem of dielectric and magnetic spherical hollow shells, consisting of a linear, homogeneous and isotropic parent material, subjected to an external potential, $U_{ext}(\mathit{r})$, of any spatial form (either dc (static) or ac of low-frequency (quasistatic limit)). By applying the method-of-linear-recursive-solution (MLRS) to the Laplace equation, we calculate analytically the internal, $U_{int}(\mathit{r})$, and total, $U_{tot}(\mathit{r})$, potentials in respect to the external one, $U_{ext}(\mathit{r})$. From $U_{int}(\mathit{r})$ and $U_{tot}(\mathit{r})$ we calculate all relevant scalar and vector physical entities of interest. The MLRS unveils straightforwardly the existence of two distinct depolarization factors, $N_l=l/(2l+1)$ and $N_{l+1}=(l+1)/(2l+1)$, both depending on the degree, $l$, however not on the order, $\mathrm{m}$, of the mode of the external potential, $U_{ext}^{(l,m)}(\mathit{r})$. These depolarization factors, $N_l$ and $N_{l+1}$, originate from the outer, $r=\mathrm{b}$, and inner, $r=\mathrm{a}$, surfaces and are accompanied by two extrinsic susceptibilities, ${\chi }_{e,l}^{ext}={\chi }_e/(1+N_l{\chi }_e)$ and ${\chi }_{e,l+1}^{ext}={\chi }_e/(1+N_{l+1}{\chi }_e)$, respectively. Importantly, $N_l+N_{l+1}=1$, irrespective of the degree, $l$, as it should. The properties of spherical hollow shells are investigated through analytical modeling and detailed simulations, with emphasis on application-relevant scenarios including resonance phenomena in scattering, quantitative materials characterization, and shielding/distortion. The generic MLRS strategy provides a flexible and reliable route for analyzing depolarization processes in other dielectric and magnetic building-unit geometries encountered in practice. Full article

Noble metal nanostructures provide versatile platforms for light manipulation through localized surface plasmon resonances (LSPRs). Among them, triangular silver nanoplates (AgNPTs) exhibit strong field-enhancement and spectral tunability, yet assembling them reproducibly on solids is challenging. We report a two-step functionalization strategy for constructing ordered AgNPT dimers on silica substrates, combining 3-aminopropyltriethoxysilane (APTES) anchoring with 1,4-butanedithiol bridging. AFM reveals face-to-face dimers with well-defined sub-nanometer gaps. Large-area AFM statistics collected over multiple regions (N = 80 nanoplates per condition) confirm reproducible and selective vertical dimerization. Extinction spectroscopy reveals sequential dielectric and coupling effects: thiol adsorption red-shifts the main resonance from 700 to 780 nm because of increased local refractive index and near-field damping, whereas dimerization partially restores it to ≈750 nm, consistent with plasmon hybridization within rigid ∼0.7 nm molecular gaps, where nonclassical moderation may occur but classical hybridization fully explains the observed shifts. Concomitantly, the extinction intensity doubles, following an exponential growth toward saturation during assembly. Surface-enhanced Raman scattering (SERS) measurements using 4-mercaptobenzoic acid (4-MBA) confirm a fourfold increase in the SERS enhancement factor from monolayer to bilayer, consistent with near-field coupling and hotspot formation at interplate junctions. Quantitative plasmon sensitivity analysis yields comparable results between experiments and finite-difference-time-domain simulations, confirming that the observed spectral shifts arise from near-field coupling and dielectric modulation rather than ensemble effects. This reproducible methodology enables precise tuning of NPT orientation, spacing, and optical response, providing a robust platform for enhanced sensing, SERS, and nanophotonic device engineering. Full article

Surface Acoustic Wave (SAW) technology, long central to analog signal processing and RF filtering, is undergoing a major renewal. Driven by advances that decouple SAWs from traditional piezoelectric materials and fixed-function devices, the field is gaining unprecedented control over acoustic, optical, and electronic interactions at the micro and nanoscale. This review synthesizes these developments across four fronts: new physical mechanisms for SAW manipulation, emerging material platforms, ranging from thin films to 2D systems, along with reconfigurable device architectures and circuits, and the expanding landscape of applications they enable. Optical methods are reshaping how SAWs are generated and controlled, bypassing the limits of conventional electromechanical coupling. Coherent optical excitation of high-Q SAW cavities via Brillouin-like optomechanical interactions now grants access to modes in non-piezoelectric substrates such as diamond and silicon, while on-chip SAW excitation in photonic waveguides through backward stimulated Brillouin scattering opens new integrated sensing routes. In parallel, magneto-acoustic experiments have revealed nonreciprocal SAW diffraction from resonant scattering in magnetoelastic gratings. On the device side, ZnO thin-film transistors integrated on LiNbO₃ exploit acoustoelectric coupling to realize voltage-tunable phase shifters; UHF Z-shaped delay lines achieve high sensitivity in a compact footprint; and parametric synthesis of wideband, multi-stage lattice filters targets 5G-class performance. Atomistic simulations show that SAW propagation in 2D MXene films can be engineered via surface terminations, while aerosol jet printing and SAW-assisted particle patterning provide agile, cleanroom-light fabrication of microfluidic and magnetic components. These advances enable applications ranging from hybrid quantum systems and quantum links to lab-on-a-chip particle control, SBS-based and UHF sensing, reconfigurable RF front-ends, and soft robotic actuators based on patterned magnetic composites. At the same time, optical techniques offer non-contact probes of dissipation, and MXenes and other emerging materials open new regimes of acoustic control. Conclusively, they are transforming SAW technology into a versatile, programmable platform for mediating complex interactions in next-generation electronic, photonic, and quantum systems. Full article