Effect Of Incidence Angle Research Articles

On reflection and transmission of qP waves in initially stressed viscoelastic triclinic layer between distinct triclinic geomedia with sliding interface

The present study dwells with the propagation of quasi seismic qP waves in an initially stressed highly anisotropic viscoelastic triclinic layer which is in sliding contact with the upper initially stressed viscoelastic triclinic half-space. The propagation characteristics of all the reflected/transmitted wave generated by the incident qP wave through initially stressed viscoelastic triclinic substratum have been analysed in detail. Closed-form analytical expressions for reflection/transmission (RT) angles, velocity and coefficients of all the propagating waves have been derived. Effects of incident angle, layer width, initial stress and sliding parameter have been analysed and shown graphically. The energy ratio and slowness diagram have also been calculated and depicted graphically. Particular cases of free and fixed welded interface are analysed and drawn for validating the results of numerical simulation. Present work may be useful in domain with highly anisotropic viscoelastic geomedia equipped with initial stress and imperfect bonding between different interfaces such as transform-fault boundary.

2D seismic response of shallow sandy basins subjected to obliquely incident waves

Under the effects of the near-field earthquakes, the change in the incident angle of the incoming wave changes the symmetric response of basins to asymmetric. This paper investigates the 2D response of shallow trapezoidal sandy basins to incident plane SV waves. To attain this goal, a trapezoidal basin with 100 m depth, as the representative of shallow sedimentary basins, with an inclined bedrock angle of 10° was selected. These values fall inside of the ranges of the shallow basin depth and bedrock angle of several real basins. To make the results useful in engineering affairs, three different sand types belonging to the different class of soils, with respect to the soil classification codes, were selected. The constructed models were subjected to the collection of 24 earthquakes with different PGA's of 0.1, 0.2, 0.3 and 0.4 g using a fully nonlinear method. The results showed that the change in the incident angle of the motions not only affects the response at two basin edges but also influences the response of the central part. Among different sandy basins, the behavior of the basin with medium dense sand is less affected by the change in the wave incident angle. For basin with loose sand, while greater maximum spectral amplifications happen at the backward direction of the basin, the forward direction is less affected by the change in the wave incident angle. A different pattern was seen for basin with dense sand. Greater maximum spectral amplifications were seen at the forward direction of the basin. Regarding the effect of motion incident angle on the amplification frequency of shallow basins, it was seen that in case of the obliquely incident waves the spectral amplification curves of the points close to the edges have more than one (generally two) maximum points. Besides, unlike the vertical incident wave case that the SAF curves tend to almost one curve at the distant points from edges, no convergence among the SAF curves of the surface points was seen for the obliquely incident wave condition.

An explicit solution for the effect of earthquake incidence angles on seismic ductility demand of structures using Bouc-Wen model

Investigating the effect of earthquake incidence angles on the seismic ductility demands of building structures is paramount for the performance-based earthquake engineering. However, previous studies were mainly devoted to assessing the effect of earthquake incidence angles for a specific building by a refined or simplified structural model via finite element method. This method prevents researchers from studying this effect thoroughly, especially for a wide range of building vibration periods. To deal with this problem, a mass with a two-degree-of-freedom (1M2DOF) system was first introduced in this study to model building structures under biaxial earthquake excitation by incorporating the biaxial Bouc-Wen-Baber-Noori (BWBN) model. Then, an explicit solution was derived in terms of governing equation of motion (GEM) to estimate the seismic ductility demands of building structures by introducing the strength reduction factors for the 1M2DOF system. To reduce the computational complexity, model parameters involved in the derived solution were further investigated, concluding that only eleven model parameters are required to vary in structural modelling. After that, the effect of earthquake incidence angles, together with the influence of structural hysteresis characteristics, strength reduction factors, and building vibration periods were investigated, respectively, demonstrating well the applicability of the derived solution. Finally, to facilitate the application in practice, the biaxial constant strength ductility demand spectra in consideration of the effect of earthquake incidence angles were established. The investigation indicated that the derived solution is beneficial for researchers to investigate the effect of earthquake incidence angles for a wide range of building structures.

Reflection of an inhomogeneous wave at the plane boundary of initially stressed fiber-reinforced viscoelastic medium

The reflection phenomenon of attenuated waves is considered at the stress-free boundary of an initially stressed fiber-reinforced medium. An arbitrary arrangement of fibers is taken into account. The slowness vectors of reflected waves are associated with the incident wave slowness vector by generalized Snell’s law. The associated slowness vector of a particular reflected wave is resolved to yield its properties, i.e., phase velocity, attenuation angle, propagation direction and attenuation coefficient. A 4 × 4 energy matrix represents the energy fluxes of reflected waves and interaction energy. The effect of inhomogeneity and incidence angle on reflected wave characteristics are analyzed by a numerical example.

Research on Perfect and Tunable Metamaterial Absorber Based on Crosshair-shaped Graphene

Graphene, as a new nano-material, according to the physical properties of electric field localization and selective absorption on light of surface plasmon resonance (SPR), a tunable, multi-band and wide-angle perfect absorber based on crosshair-shaped graphene is devised by using the Finite Difference in Time Domain (FDTD) method. In this paper, the effects of chemical potential, relaxation time, and incident angle of light on the absorptivity of graphene are systematically discussed. The simulation experiment shows that there are two absorption peaks with perfect absorption rate appeared in the study range, and the maximum modulation index can be obtained by changing the relaxation time. Finally, it proves that the absorber is insensitive to wide-angle of light. Thus, it is able to be concluded that the absorber has a great reference value to sensor, wireless communication, biomedical and other fields.

Studying the Effect of Light Incidence Angle on Photoelectric Parameters of Solar Cells by Simulation

It is crucial to examine the dependence of photoelectric parameters of solar cells on the light incidence angle. In the present study, two solar cell models have been developed using the Sentaurus Technology Computer-Aided Design software package. The light spectrum AM1.5 has been directed on the frontal surface of solar cells at different angles. It has been found that the angular coefficient of the photoelectric parameters of a solar cell with nanoparticles included, is two times more than that of a simple solar cell. Besides, it has been found that the efficiency of platinum nanoparticles induced solar cells is 2.15 times greater than simple solar cell efficiency. When the light incidence angle has been varied from 0 to 60 degrees, the short-circuit current has changed by 11% for simple solar cells and by 10% for solar cells with nanoparticles. Further, it has been observed that the variation of power for simple solar cells is 12.5%, while it is 10.5% for solar cells with nanoparticles. In addition, the short-circuit current of solar cells with nanoparticles has been found to be linear within a light incidence angle ranging from 0 to 60 degrees.

Seismic analysis of a lined tunnel in a multi-layered TI saturated half-space due to qP1-and qSV-waves

A special indirect boundary element method (IBEM) is presented to study the in-plane scattering by a lined tunnel embedded in a multi-layered TI saturated half-space. By integrating the full-space and half-space Green’s functions for the inclined distributed load and pore pressure, these singular-free kernels enables the method to treat an arbitrarily shaped tunnel with a superior flexibility and high efficiency in comparison to the traditional IBEM. For the total system, the substructure process is implemented to decompose the model into a layered TI saturated half-space region and a lining region filled with isotropic elastic medium. The dynamic stiffness matrix method developed by the authors is adopted to solve the free field of the exterior half-space, and the scattered fields existed in the exterior and interior lining regions are simulated by the half-space and full-space Green’s functions in a single-layer potential representation, respectively. Then the total wave-fields in the half-space region can be expressed as the superposition of free-field and scattered field, and the tunnel region merely contains the scattered field. The compatibility conditions on inner and outer interfaces enclosing the lining are satisfied to couple these sub-regions to the original one. The present method is calibrated by comparison with available limited cases. Displacement and dynamic hoop stress concentration at the inner surface of the lining are calculated in the frequency domain to portray the effects of anisotropy degree, drainage condition, incident angle, frequency and layering on the seismic response. Results show that the decrease of anisotropy degree generally leads to larger amplitudes of surface displacement and the stress. Prominent amplification of displacement and stress can be observed for the two-phase medium model in comparison to the one-phase model although the vertical displacement is hardly affected by the drainage condition at the lining-rock interface. When taking the layering into account, the vertical displacement maximum is increased by about 32%, while the DHSC amplitudes at different cases tend to become larger on the whole compared to those for the homogeneous half-space.

A simplified approach for including the incidence angle effect in seismic risk assessment

AbstractA simplified procedure is developed to consider the azimuthal orientation of buildings when estimating seismic risk. Two square‐plan reinforced concrete building models are considered as a testbed, one with similar and one with dissimilar properties along the two principal horizontal axes. The fragility of both structures is analysed using a set of ground motion records rotated to multiple incidence angles to develop orientation‐dependent fragility functions. It has been observed that, re‐orienting all records so that these structures have the same azimuth vis‐à‐vis the corresponding epicentre leads to significant differences compared to assuming random orientations. Additional results stemming from single‐degree‐of‐freedom oscillators further confirm such findings, showing a dependence to the proximity to the faults and the level of dissimilarity in the principal horizontal axes of the structure. The end results point to a non‐negligible bias in assessment studies when a structure's orientation with respect to governing rupture scenarios is not taken into account. It is shown that the median of fragility curves calculated for un‐rotated incidence angles can be bias‐corrected through shifted by an amount that depends on the azimuthal orientation and level of axes‐dissimilarity of structures.

A Model-Derived Empirical Formulation for Wave Run-Up on Naturally Sloping Beaches

A new set of empirical formulations has been derived to predict wave run-up at naturally sloping sandy beaches. They are obtained by fitting the results of hundreds of XBeach-NH+ model simulations. The simulations are carried out over a wide range of offshore wave conditions (wave heights ranging from 1 to 12 m and periods from 6 to 16 s), and surf zone (Dean parameters aD ranging from 0.05 to 0.30) and beach geometries (slopes ranging from 1:100 to 1:5). The empirical formulations provide estimates of wave set-up, incident and infragravity wave run-up, and total run-up R2%. Reduction coefficients are included to account for the effects of incident wave angle and directional spreading. The formulations have been validated against the Stockdon dataset and show better skill at predicting R2% run-up than the widely used Stockdon relationships. Unlike most existing run-up predictors, the relations presented here include the effect of the surf zone slope, which is shown to be an important parameter for predicting wave run-up. Additionally, this study shows a clear relationship between infragravity run-up and beach slope, unlike most existing predictors.

Interaction of waves with a sliding viscoelastic layer

In this work, a theoretical analysis of bulk wave interaction with a sliding layer has been considered. The layer is assumed to be sliding with a constant velocity. The effect of the sliding velocity on the reflection and transmission behaviors has been studied. A low loss viscoelastic property is considered for the layer, which is held between two identical grounded elastic half-spaces. The governing equations for the dilatoric and deviatoric wave components in the viscoelastic layer are derived. The problem is solved using a coordinate transform based on an appropriate change in the wave velocities. The solutions are then used to calculate the reflection and transmission coefficients by solving the system of linear equations. The coefficients are observed to be affected remarkably by the sliding velocity of the layer. The effects of incidence angle and frequency of an incoming wave on the reflection and transmission characteristics are studied. The conditions for the existence of critical incidence are also discussed. This work gives some theoretical understanding of the wave characteristics in a sliding medium, which is expected to be useful in applications related to wave-based actuation and manipulation.

Experimental Investigation of Effects of Reynolds Number and Incidence Angle on Secondary Flow within a Linear Blade Cascade

Experimental Investigation of Effects of Reynolds Number and Incidence Angle on Secondary Flow within a Linear Blade Cascade

Effect of Incidence Angle on the Spatial-Average of Incident Power Density Definition to Correlate Skin Temperature Rise for Millimeter Wave Exposures

This article reports on an intercomparison study on the effect of the incidence angle on the spatial average of incident power density (PD) and resultant temperature rise using computational and thermographic measurement approaches. Two definitions of the spatial average of incident PD—the peak spatial-average normal component of the Poynting vector and peak spatial-average norm of the Poynting vector—were compared. First, an intercomparison of incident PD and temperature rise in a layered skin model was conducted for a 4 × 4 dipole array antenna. The variations caused by antenna type, antenna-body distance, and skin model to these definitions were then discussed. The results revealed that both definitions are in good agreement and correlate with the peak temperature rise for small or moderate incidence angles. The heating factor was enhanced for transverse-magnetic-like polarized waves for peak spatial-average normal component of the Poynting vector for large-angle incidences because of the Brewster effect. The normal incidence scenario was confirmed to be essential for considering the peak skin temperature rise.

Investigations of the incident light angle effect on the organic photovoltaics devices performance using varied acceptor ratio

Organic photovoltaic devices (OPV) have received great attention in the last decades, due to their advantages in fabrication processes and the low cost of organic material. In this report, the active layer of the device is prepared from poly (3-hexylthiophene) (P3HT) (20 K): (phenyl C61 butyric acid methyl ester) (PCBM) with various acceptor ratios (1:0.5–2). The surface morphology of the active layer thin films was investigated by analysing their optical microscope image using Image J software. The active layer thin films were characterized optically to calculate the optical properties of the active layer. The internal absorption of the device is calculated using the optical modelling technique. Then, optical modelling is utilized to optimize the device performance based on changing the donor: acceptor ratio and predicting the internal quantum efficiency (IQE) of the devices. The optimum current density values of the device (Jsc) were found to vary in about (11–14 mA cm−2) compared with the measured data (3.8–8 mA cm−2). The internal quantum efficiency (IQE) was identified from measured and modelled Jsc and its percentage confirmed that the best blending ratio of P3HT: PCBM is (1:0.8–1), associated with the IQE percentage 54%–45%. Additionally, the effect of incident light angle was examined by using optical modelling technique and the findings revealed that the current density Jsc, gradually increased with the incident angle between (0–45) degrees and then suddenly decrease at the angle of 60 degrees due to the reflection that occurs at Air/glass interface at large angles.

Influence of surface structure on D retention and erosion behaviours of RAFM steel with D-plasma exposure

As the first wall candidate material in the future fusion device, Reduced Activation Ferritic/Martensitic (RAFM) steel represented by CLF-1 steel was further investigated on the deuterium (D) erosion and retention behaviours. The influences of the surface conditions, including surface morphology, W-enriched structure and the original surface roughness, of the surface conditions including the sample temperature, W-enriched structure and the original surface roughness are mainly discussed. The results showed that with the increase of the sample temperature of CLF-1 steel during D-plasma exposure, the surface morphology changed obviously, and the grooves/pits formed by the erosion on the sample surface are deepened and the boundary becomes obvious. Then, the granular nanostructures appeared at the erosion edges and covered the grooves, eventually forming the nanoclusters structure on the surface. At the same time, TEM results showed that the thickness and content of W atoms on the surface increased. Under the combined action of the above surface conditions, both the sputtering rate and total D retention amount of CLF-1 steel decrease. Under the current experimental parameters, with the increase of the initial surface roughness, the sputtering morphology and the surface roughness of CLF-1 steel changed to different degrees after erosion of D, which eventually led to the slightly increase of the sputtering rate. The effect of incident D-plasma angle on the sputtering and redeposition behaviour of the material may explain this phenomenon. Besides, both the specific surface area of the contact plasma and the erosion behaviour of the material by D-plasma increased with the original surface roughness. The D releasing peak, thermal desorption temperature and total D retention amount of CLF-1 steel samples decrease with the original roughness of CLF-1 steel, which is mainly caused by the increase of D diffusion on the surface. At present, it can be found that the W-enriched surface behaviour induced by D-plasma exposure as well as the change of roughness and morphology lead to the decrease of the sputtering rate of RAFM steel with fluence, energy and sample temperature.

Angular dependence of localized mode of chalcogenide photonic crystal

In this paper, we have designed a one-dimensional chalcogenide photonic crystal using As2Se3/air multilayered structure. A single defect is introduced by replacing As2Se3 layer with As2S3. In the proposed structure, the well-known transfer matrix method is employed to determine the transmission spectra for both TE (transverse Electric) and TM (transverse Magnetic) modes. A theoretical analysis of effect of incidence angle on defect modes is presented. Variation in incidence angle causes the shift in defect modes.

Effects of wind direction and building array arrangement on airflow and contaminant distributions in the central space of buildings

Buildings are physical obstacles that diminish the benefits of wind by creating turbulence and reducing airflow velocities in urban settings. Particularly in the inner garden or amenities situated at the pedestrian level in the central space of a group of buildings, the efficiency of pollutant dispersion determines air quality and outdoor health. In this study, the effects of incident wind angles on wind velocity and pollutant distribution inside the central space of two building arrays arranged in ‘L’ and ‘U’ shapes were examined using computational fluid dynamics simulations. The ‘L’-shaped array performed better than the ‘U’-shaped array by forming a smaller low-wind-velocity (LWV) zone in the central space of the buildings (34.9%–76.11 % of the total space). The ‘L’-shaped array performed best at an incident wind angle of 225°, in which the LWV zone covered only 34.52 % of the central space. A 90° incident angle produced the largest LWV zone (81.80 %) for the ‘U’-shaped array. The ‘L’-shaped array generally distributed pollutants better than the ‘U’-shaped array. However, the ‘U’-shaped array with a 180° wind angle had a smaller high pollutant concentration area than the ‘L’-shaped array with a wind angle of 225° (Kc > 218.5 covering only 0.37 %). The worst vertical dispersion corresponded to a 135° wind angle for the ‘L’-shaped array, which recorded the highest Kc at the mid-level of the building. In conclusion, the appropriate selection of building array designs and their orientations allows for the most effective use of wind flow to enhance ventilation and pollutant dispersion.

Electromagnetic characterization of strong-coupled Omega-type bianisotropic metamaterials using the state transition matrix method

A feasible extraction procedure is proposed to retrieve the diagonal tensor elements of the permittivity and permeability, and the magnetoelectric coupling coefficient of Omega-type biansiotropic metamaterials (MMs). The procedure is based on the state transition matrix approach and uses non-iterative closed-form expressions between constitutive parameters and scattering (S-) parameters to achieve such determination using S-parameters for normal incidence and oblique incidence of TE and TM modes (a desirable feature from practical point of view). S-parameter simulations of a bianisotropic MM slab constructed by edge-coupled resonators are performed using a 3D electromagnetic simulator program and used to validate the proposed procedure and compare its accuracy against previously developed extraction procedures. The effects of incidence angle, S-parameters' noise, and dimensional variations (fabrication tolerances) on the extracted parameters of the examined MM slab are investigated.

Dynamic Cosine Method for Normalizing Incidence Angle Effect on C-band Radar Backscattering Coefficient for Maize Canopies Based on NDVI

Wide mode SAR images have an apparent incidence angle effect. The existing incident angle normalization methods assume that the relationship between the incident angle (θ) and the backscattering coefficient (σPQ) does not change with the growth stage of crops, which is in conflict with the real-life situation. Therefore, the normalization results of σPQ based on these existing methods will affect the accuracy of object classification, target recognition, and land surface parameter inversion. Here, the change in θ-σPQ relationship was investigated based on time-series (April to October) σPQ of maize canopies in northeast China, and a dynamic method based on normalized difference vegetation index (NDVI) was developed to normalize the effect of θ on σPQ. Through the accuracy evaluation, the following conclusions are obtained: (1) the dependence (referring to N) of Sentinel 1 C-band σPQ on θ varies with maize NDVI. In addition, the value of N changed from 9.35 to 0.66 at VV polarization from bare soil to biomass peak, and from 6.26 to 0.99 at VH polarization; (2) a dynamic method was proposed to quantify the change of N based on its strong correlation with NDVI, indicated by R2 of 0.82 and 0.80 for VV and VH polarization, respectively; and (3) the overall root mean square error of normalized σPQ based on the newly-developed dynamic method is 0.51 dB, and this accuracy outperforms the original first-order cosine method (1.37 dB) and cosine square law method (1.08 dB) by about 63% and 53% on the whole. This study provides a dynamic framework for normalizing radar backscatter coefficient, improving the retrieval accuracy of land surface parameters from radar remote sensing.

Faraday rotator made of conjugated magneto active photonic crystal heterostructures

Two defective conjugated magneto active photonic crystals are proposed in this paper for fabrication of Faraday rotators. Optical features of the suggested structures are studied using 4 × 4 transfer matrix method and taking into consideration of the couplings of polarization states. Band structure of the crystals including generation of stop bands and resonant modes localizations are studied by exploring the dependence of the crystals' transmittance on the period number of the layers. It is shown that desirable responses are obtained by just very low number of periods. Furthermore, optical anisotropy of the crystals is considered to be purely magnetic field-induced. Then in addition to studying the dependencies on structural parameters, connection between wave incident angle and magneto-optical effects (Faraday rotations and changes of the ellipticity angle) are discussed in detail. Results clearly show the ease of tunability of the structures' responses in this way which is of prime importance from experimental point of view. Furthermore, the proposed structures offer remarkable Faraday rotation angles when transmittance amounts remain high enough simultaneously. Thus it seems that these crystals might be useful for fabrication of polarization dependent sensor/transducers based on Faraday rotators which are vital elements in development of integrated circuits as well as imaging systems.

Hyperspectral LiDAR-Based Plant Spectral Profiles Acquisition: Performance Assessment and Results Analysis

In precision agriculture, efficient fertilization is one of the most important pursued goals. Vegetation spectral profiles and the corresponding spectral parameters are usually employed for vegetation growth status indication, i.e., vegetation classification, bio-chemical content mapping, and efficient fertilization guiding. In view of the fact that the spectrometer works by relying on ambient lighting condition, hyperspectral/multi-spectral LiDAR (HSL/MSL) was invented to collect the spectral profiles actively. However, most of the HSL/MSL works with the wavelength specially selected for specific applications. For precision agriculture applications, a more feasible HSL capable of collecting spectral profiles at wide-range spectral wavelength is necessary to extract various spectral parameters. Inspired by this, in this paper, we developed a hyperspectral LiDAR (HSL) with 10 nm spectral resolution covering 500~1000 nm. Different vegetation leaf samples were scanned by the HSL, and it was comprehensively assessed for wide-range wavelength spectral profiles acquirement, spectral parameters extraction, vegetation classification, and the laser incident angle effect. Specifically, three experiments were carried out: (1) spectral profiles results were compared with that from a SVC spectrometer (HR-1024, Spectra Vista Corporation); (2) the extracted spectral parameters from the HSL were assessed, and they were employed as the input features of a support vector machine (SVM) classifier with multiple labels to classify the vegetation; (3) in view of the influence of the laser incident angle on the HSL reflected laser intensities, we analyzed the laser incident angle effect on the spectral parameters values. The experimental results demonstrated the developed HSL was more feasible for acquiring spectral profiles with wide-range wavelength, and spectral parameters and vegetation classification results also indicated its great potentials in precision agriculture application.