Incident Angle Research Articles

The Generation of Superinertial Coastally Trapped Waves by Scattering at the Coast

Abstract A series of idealized numerical simulations is used to examine the generation of mode-one superinertial coastally trapped waves (CTWs). In the first set of simulations, CTWs are resonantly generated when freely propagating mode-one internal tides are incident on the coast such that the angle of incidence of the internal wave causes the projected wavenumber of the tide on the coast to satisfy a triad relationship with the wavenumbers of the bathymetry and the CTW. In the second set of simulations, CTWs are generated by the interaction of the barotropic tide with topography that has the same scales as the CTW. Under resonant conditions, superinertial coastally trapped waves are a leading order coastal process, with alongshore current magnitudes that can be larger than the barotropic or internal tides from which they are generated.

Performance Improvement of Space-Target Classifier Based on Convolutional Neural Network Using Angle of Incidence

Performance Improvement of Space-Target Classifier Based on Convolutional Neural Network Using Angle of Incidence

Simplistic metasurface design approach for incident angle and polarization insensitive rcs reduction

This paper proposes the design of a metasurface for polarization and incident angle-insensitive RCS reduction applications. An ellipse-shaped unit cell is utilized as a polarization converter, which is then arranged to form a checkerboard surface. While a single layer checkerboard structure gives a wideband RCS reduction, a double layer structure yields polarization and incident angle independent operation. The two layers have unit cells rotated 450 to each other. Experimental results demonstrate an RCS reduction bandwidth of around 90%. Further the RCS reduction remains stable with polarization and incident angle variation.

Dielectric metamaterials with effective self-duality and full-polarization omnidirectional brewster effect

Conventional dielectric solid materials, both natural and artificial, lack electromagnetic self-duality and thus require additional coatings to achieve impedance matching with free space. Here, we present a class of dielectric metamaterials that are effectively self-dual and vacuum-like, thereby exhibiting full-polarization omnidirectional impedance matching as an unusual Brewster effect extended across all incident angles and polarizations. With both birefringence and reflection eliminated regardless of wavefront and polarization, such anisotropic metamaterials could establish the electromagnetic equivalence with “stretched free space” in transformation optics, as substantiated through full-wave simulations and microwave experiments. Our findings open a practical pathway for realizing unprecedented polarization-independence and omnidirectional impedance-matching characteristics in pure dielectric solids.

Three-Dimensional Nanoscale Imaging of SiO2 Nanofiller in Styrene-Butadiene Rubber with High-Resolution and High-Sensitivity Ptychographic X-ray Computed Tomography

Abstract SiO2 aggregates in styrene-butadiene rubber (SBR) were observed using ptychographic X-ray computed tomography (PXCT). The rubber composites were illuminated with X-rays focused by total reflection focusing mirrors, and the ptychographic diffraction patterns were collected using a CITIUS detector in the range of −75° to +75° angle of incidence. The projection images of the rubber composites were reconstructed with a two-dimensional resolution of 76 nm, and no significant structural changes were observed during the PXCT measurements. A three-dimensional image of the rubber composite was reconstructed with an isotropic resolution of 98 nm. Segmentation of SiO2 from the SBR, based on a histogram analysis of the phase shift, revealed a fragmented network structure of interconnected SiO2 aggregates.

MXene-based semi-circle with a thin wire-shaped resonator wideband polarization-insensitive solar absorber

Fossil fuels’ supply peaks, decreases, and shortages are determined by their proven reserves, research, and consumption rates. With a large upfront cost, renewable and alternative energy sources are essential to solving the twin issues of energy and climate change. Solar absorbers are an excellent way to use renewable energy from the environment. This paper suggested an MXene-based semi-circle with a thin wire-shaped resonator (MSCWTWSR) solar absorber where the resonator layer consists of MXene material and Fe is used as substrate layer and the resonator has semi-circle and thin wire geometry which effectively absorbs the sun radiation with wideband. This proposed MSCWTWSR solar absorber works at 200–3000 (nm) wavelength and has more than 93% average absorption. The first band bandwidth of this MSCWTWSR solar absorber is 400 (nm), the second band is 530 (nm), and the third band is 470 (nm). This structure got more than 93% absorption in the AM 1.5 solar irradiation configuration. The structure gives in the Transverse electric (TE) field and Transverse magnetic (TM) field and the structure has polarization for insensitive. Furthermore, there is also investigated different incidence angles. A suggested article includes sections on testing for electric and magnetic intensities with a comparison table. The suggested solar absorber is employed in a distinct thermal heating application since MXene has a low thermal resistance and good thermal stability.

Spin/valley dependent dwell time in an 8-Pmmn borophene junction

Spin/valley dependent dwell time in 8-Pmmn borophene junction under Rashba spin–orbit interaction (RSOI) is studied. The dwell time as well as transmission probability for incident electrons with spin-up show a different behavior than the incident electrons with spin-down, and these quantities can be controlled effectively by the junction direction, incident angle, the RSOI strength and the barrier width. Also, the dwell time is dependent on the degree of freedom of the valley and shows oscillating behavior with the increase of the barrier width. The spin polarization and spin filtering in 8-Pmmn borophene junction under RSOI can be obtained in the time domain.

Seismic performance assessment of high arch dams considering the pulse-like and directionality effects of near-fault ground motions

This paper investigates the pulse-like and directionality effects of near-fault horizontal ground-motion records on the seismic performance of high arch dams. A 3-dimensional arch dam-reservoir-foundation finite-element model is built. Two near-fault bidirectional ground-motion suites (i.e. ordinary and pulse-like suite) are collected. The fault-normal and fault-parallel orientations of the horizontal ground-motion records are rotated to reflect the directionality effect. Nonlinear dynamic analyses are further implemented for the high arch dam excited by both near-fault ground motions with different incidence angles. The results show that the pulse-containing ground-motion records can yield more notable dynamic response and damage for high arch dams as compared to the ordinary records. Moreover, with changing the incidence angles, both the dam dynamic response and damage metrics exhibit periodic variation and constant trends for the pulse-containing and ordinary ground-motion cases, respectively. Therefore, the directionality effect has a significant influence on the seismic performance of high arch dams excited by pulse-containing ground-motion records. Compared with the near-fault ordinary ground motions, the pulse-like ground motions will induce a 40 %-increase in the concrete damage volume of high arch dams. In addition, peak ground velocity could be regarded as a preferable intensity measure for assessing the seismic damage of high arch dams.

Diffraction tomography for incident Herglotz waves

Abstract Diffraction tomography is an inverse scattering technique used to reconstruct the spatial distribution of the material properties of a weakly scattering object. The object is exposed to radiation, typically light or ultrasound, and the scattered waves induced from different incident field angles are recorded. In conventional diffraction tomography, the incident wave is assumed to be a monochromatic plane wave, an unrealistic simplification in practical imaging scenarios. In this article, we extend conventional diffraction tomography by introducing the concept of customized illumination scenarios, with a pronounced emphasis on imaging with focused beams. More specifically, we consider incident Herglotz waves and extend the classical Fourier diffraction theorem to this setting. This yields a new two-step reconstruction process which we comprehensively evaluate through numerical experiments.

Aero-optical effects of a hypersonic vehicle based on the refractive index step ray tracing method

The aero-optical effect caused by the high-speed flight of aircraft can affect the accuracy of astronomical navigation, so studying the laser transmission characteristics in high-speed flow fields is essential. This study adopts a 3D spherical blunt cone model as the physical aircraft model, incorporates the latest reanalysis data from the National Centers for Environmental Prediction as atmospheric parameters, and uses Fluent software to establish a hypersonic aircraft external flow field model. The ray tracing error is calculated using a method based on the refractive index step size. Results indicate that, under the conditions of flying altitude of 5 km and incident angle of 45°, the proposed ray tracing method has better accuracy than the traditional method. Compared with the Runge–Kutta method and the method based on geometric step size, the proposed ray tracing method reduces the error by 46.4% and 12.5%, respectively, at the flight Mach number of 5.

Design and investigation of indium tin oxide-based transparent broadband microwave absorbers

Abstract This paper presents the design of a novel wideband transparent microwave absorber based on indium tin oxide (ITO). The absorber adopts a multilayer structure, with the top layer composed of a nested square structure made of ITO material, an intermediate dielectric layer of polyvinyl chloride (PVC), and a bottom layer of polyethylene terephthalate (PET) coated with ITO as the reflector. By optimizing structural parameters such as the thickness of the ITO film and the dimensions of the spacer layer, efficient broadband microwave absorption exceeding 90% is achieved within the frequency range of 2.43 to 5.67 GHz, while simultaneously meeting requirements for optical transparency and broadband performance. Simulation experiments and theoretical analyses demonstrate excellent polarization and incident angle stability of the absorber structure. Finally, samples are fabricated using screen printing technology, and free-space testing results are consistent with simulation predictions, validating the feasibility of the design.

Incidence Angle Effect: Validation of New Measurement Methods for IEC 61853‐2

ABSTRACTThe incidence angle effect causes a decrease in the photogenerated current of PV modules when they are subject to incident irradiance at wide angles: Its relevance should be quantified for accurate energy yield purposes and has recently gained significance due to the rising interest in novel integrated PV applications, where vertical or nonoptimal tilt are favored (e.g., in urban structures, in agrivoltaics, and vehicles). The international standard IEC 61853‐2 presents both outdoor and indoor measurement methods: However, the indoor measurement method for commercial‐size modules is often impractical due to irradiance uniformity limitations on the volume spanned by the tested module upon rotation in most of the solar simulators available on the market. In recent years, new solutions have been proposed to overcome these limitations and allow wider adoption of this standard: However, method validations and interlaboratory comparisons have been conducted so far only on small‐area samples, and a real validation on commercial‐size modules is still missing. In this work, we aim at filling this gap, reporting the results of an interlaboratory comparison conducted within the international project team that is currently working at the new edition of IEC 61853‐2. The results show a remarkable agreement between different measurement methods, thus validating more options for the evaluation of this important effect.

High-precision and large-range deflection of light beams with fast steering mirrors

Fast steering mirrors (FSMs) offer a potential alternative for large-range deflection of light beams. However, for a large-stroke FSM, its pointing precision is unacceptably deteriorated due to the actuator non-uniformity, mechanical axis coupling, and the coupling of line-of-sight (LOS) kinematics. This Letter proposes a comprehensive beam-pointing algorithm by decoupling the LOS kinematic model and establishing a two-dimensional correction mapping to compensate for the non-uniformity and mechanical coupling. Moreover, the incident angle is calibrated by a non-contact method to construct the LOS kinematic model accurately. The experimental results proved that the beam-pointing accuracy can achieve a sub-milliradian level within the square field of regard (FOR) of ±25° horizontally and ±14° vertically. A pointing error of 0.87 mrad can be guaranteed within the horizontal range of −30° to 36° and the vertical range of ±24°. Therefore, the proposed method can achieve high-precision beam pointing in a large FOR and contributes to the miniaturization of optical systems.

Comparative Analysis of Two Different MIM Configurations of a Plasmonic Nanoantenna

AbstractTwo plasmonic nanoantenna configurations—nanodisk and nanostrip arrays—in a metal–insulator-metal (MIM) setup were proposed, optimized, and compared by simulating their optical properties in three-dimensional models using COMSOL Multiphysics software. The optical responses, including electric field enhancement, absorption, reflection, and transmission spectra, were systematically investigated. Optimized geometrical parameters led to a significant enhancement of the electric field within the gap layers and almost perfect light absorptance for both structures. The results showed that the enhancement of the electric field depends on the polarization of the incident light. For both polarizations, the periodic circular nanodisk array showed a stronger field enhancement with an electric field enhancement factor of 6.6 × 106 and TE polarization, and a larger absorptance of 98% at its dipole resonance wavelength, indicating the fundamental plasmonic mode. In addition, weaker resonant modes were observed in the absorptance and reflectance spectra of both nanostructures, with the nanostrips exhibiting sharper and stronger higher-order modes, making them suitable for applications requiring precise wavelength selectivity and narrow-band responses. Despite their different geometric shapes, both structures exhibited similar optimized metal film thickness and nanoparticle height, comparable modes in number and position, and identical optimized light incidence angles. Furthermore, increasing the dielectric gap layer thickness and optimizing it to a specific value revealed its ability to measure the refractive index, making it a promising candidate for sensing applications.

Nonlinear Seismic Response of Tunnel Structures under Traveling Wave Excitation

Tunnels traditionally regarded as resilient to seismic events have recently garnered significant attention from engineers owing to a rise in incidents of seismic damage. In this paper, the reflection characteristics of the elastic plane wave incident on the free surface are analyzed, and the matrix analysis method SWIM (Seismic Wave Input Method) for the calculation of equivalent nodal loads with artificial truncated boundary conditions for seismic wave oblique incidence is established by using coordinate transformation technology, according to the displacement velocity and stress characteristics of a plane wave. The results show that the oblique incidence method is more effective in reflecting the traveling wave effect, and the “rotational effect” induced by oblique incidence must be considered for P wave and SV wave incidence, including the associated stress and deformation. This effect exhibits markedly distinct rotational phenomenon. In particular, the P wave incidence should be focused on the vault and the inverted arch due to the expansion wave. With the increase of the oblique incidence angle, the structural stress and deformation are rotated to a certain extent, and the values are significantly increased. Simultaneously, the shear action of the SV wave may result in “ovaling” of the tunnel structure, thereby facilitating damage to the arch shoulder and the sidewall components. As the oblique incidence angle, the potentially damaging effects of the “rotational effect” to the vault and the inverted arch, but the numerical value does not change significantly. In addition, in comparison to a circular cross-section, the low-frequency amplification of seismic waves in the surrounding rock and the difference of frequency response function in different parts of the lining are more pronounced. In particular, the dominant frequency characteristics are significant at P wave incidence and the seismic wave signal attenuation tends to be obvious with increasing incidence angle. In contrast, SV waves exhibit more uniform characteristics.

Dark field photon scattering state measurements from bumps on a gold nanofilm

Abstract A dark and bright field (BF) imaging technique explored plasmonic phenomena arising from bumps on a gold nanofilm coated on a silica substrate. The study employs dark field (DF) polarization indirect microscopic imaging to investigate the scattering photon state and reveal the spatial distribution characteristics with distinct multipolar features, contrasting with those observed in the BF imaging configuration. Computational simulations utilizing the finite-difference time-domain method were conducted to understand this behaviour further and consider the experimental setup’s impact. The observations of varying multipolar scattering features with changes in the incident angle of the DF illumination suggest that the excitation of plasmonic effects differs for light beams incident at different angles.

Metasurface Absorber for Blood Hemoglobin Concentration.

In this study, a biosensing scenario is developed for monitoring blood quality based on the detection of blood hemoglobin concentration. The procedure involves considering the blood sample as the dielectric with different refractive indexes for different concentrations of hemoglobin. Usually, the sensitivity to design parameters is the major issue with the metasurface-based detection. To address this issue, a three-layer graphene-based wave absorber is designed and modeled using passive circuit elements. The major idea behind this work is to maximize the device sensitivity against the blood sample. The research methodology involves impedance matching between the device and the surrounding environment, while full-wave simulation is also performed and compared to ensure circuit view accuracy. The findings suggest that the proposed graphene-based absorber can efficiently monitor blood quality via dual absorption peaks. The simulation results extracted from impedance matching and the full-wave method indicate frequency shifts of the second absorption peak. These shift values are interpreted based on hemoglobin concentration. Additionally, ample analyses are provided to show the reliability of the proposed absorber against geometrical aspects, incident angle, external stimulation, and the graphene electron relaxation time.

Identification and Application of Wave Field Characteristics of Channel Waves in Extra-Thick Coal Seams

Channel wave seismic activity often occurs with thin and medium-thick coal seams being the main target layer. To address the problem of channel wave applicability detection in extremely thick coal seams, the propagation and identification characteristics of channel waves remain the focus of research. Therefore, this paper takes the in-seam wave exploration of a 27 m extremely thick coal seam as an example and uses the staggered mesh finite difference method to construct a three-dimensional medium model for numerical simulation. An analysis of the physical parameters of coal and rock, along with the dispersion characteristics of channel waves in extra-thick coal seams, is utilized, through the Zoeppritz equation and the total reflection propagation method, to calculate the imaging. We found the following: (1) The dispersion areas and weak dispersion areas along the detection direction are extremely thick coal seams. (2) There are apparent channel waves in extra-thick coal seams, with a waveform similar to body waves; the length of the wave train is shorter than that of the conventional channel wave, and the arrival time can be estimated accurately. The amplitude of the apparent channel wave is affected by the degree of dispersion, with lower attenuation and higher resolution. The characteristic of total reflection in extremely thick coal seams is that the incident angle is equal to the critical angle, and the dispersion characteristics are weak. (3) The channel waves with weak dispersion characteristics in extra-thick coal seams are mainly Love-type waves.

Symmetric engineered central cross-shaped broadband metamaterial absorber with high absorption and stability for solar sailing and solar energy applications

We propose a theoretical design and analysis of a broadband metamaterial absorber (MMA) with significant potential for solar sailing applications which is a method of spacecraft propulsion that usages the momentum of sunlight to propel a spacecraft through space. The absorber features a metal-dielectric-metal configuration with a tungsten (W) based resonator and ground plane, and a Silicon-dioxide (SiO₂) substrate. Addressing the critical need for materials that can efficiently harness solar radiation for propulsion in space, our design achieves an average absorption of 99.15 % over a broad spectrum from 250 nm to 1200 nm, covering the UV–Visible–NIR regions, with near-unity absorption peaks at 362 nm and 915.8 nm. It maintains high absorptions of 84.9 % and 86 % under transvers electric and transvers magnetic modes respectively, demonstrating excellent wide incident angle stability and polarization insensitivity due to its symmetric design. PCR values close to zero confirm its functionality as an absorber rather than a polarizer. The MMA shows minimal deformation across temperatures from 500 K to 1750 K and remains stable under various mechanical stresses, proving its durability and efficiency in space. Additionally, in solar thermophotovoltaic (STPV) systems, the MMA demonstrates high photothermal conversion efficiency (PTCE) over a wide temperature range (500 °C to 1500 °C) and different concentration factors. This dual functionality highlights its potential for both efficient space exploration and terrestrial solar energy harvesting, making it a versatile tool for future technological applications.

Modeling obliquely incident seismic wave propagation in rocks via the FDM-DEM coupling scheme: Algorithms and applications

The incidence angle of seismic waves plays a pivotal role in the stability analysis of structures in near-field zones. Despite its importance, the application of obliquely incident seismic waves within models of discontinuous media has been limited. This study introduces a novel approach that integrates the oblique incidence of seismic waves into a coupled model employing both the Finite Difference Method (FDM) and the Discrete Element Method (DEM). We validate the accuracy of seismic wave propagation under oblique incidence in two FDM-DEM coupling models—overlapping coupling and interface coupling—through comparisons with theoretical solutions. For vertically incident seismic P-waves, both models yield similar results. However, under oblique incidence, the overlapping coupling model demonstrates superior accuracy, with a maximum error of approximately 4.217 %, compared to about 10 % in the interface coupling model. Our findings also show that while the relative sizes of particle diameter and overlap length minimally affect accuracy, the arrangement of particles markedly influences the results. Furthermore, we apply this method to a slope model to investigate the failure process, revealing that the nature of the sliding body shifts from tensile sliding to tensile ejection as the incidence angle increases.