Various Angles Of Incidence Research Articles

Dynamic Response of Rock Slopes under Obliquely Incident Seismic Waves

In this study, the seismic input model of slope is proposed to investigate the dynamic response of the rock slope under obliquely incident seismic wave on the basis of the time‐domain wave analysis method. The model includes viscoelastic boundary considering the infinite foundation radiation damping and the seismic obliquely incident method. The semi‐infinite space numerical example is simulated to verify the validity and accuracy of the model. Based on the established model, the effects of the variation of the seismic wave incident angles and slope angles on the dynamic response of a rock slope are analyzed. The results demonstrate that the changes of the incident angle and the slope angle have no discernible effect on the dynamic response of the rock slope when the P wave is obliquely incident. As the SV wave is obliquely incident, the peak ground acceleration amplification coefficient along the slope surface gradually increases with the increase of the incident angle; when the slope angle gradually increases, the peak ground acceleration amplification coefficient along the slope surface will also gradually increase at the upper part of the slope. The research results can provide some basis for the pseudostatic method to determine the seismic action coefficient.

Panoramic view of particle morphology for growth mechanism exploration: A case study of micron-sized five-fold twinned Ag particles from vapor condensation

Abstract Nobel metal particles of designed morphology have found many ingenious applications in fields such as catalysis, plasmonics, metamaterials, etc. A thorough investigation of influential factors that determine the particle morphology is desirable. Micron-sized Ag particles prepared by physical vapor deposition usually result from two-step growth: condensation from dense vapor followed by continual growth of the sessile particles landing on substrate. The primary particle-substrate contact may be the decisive factor in determining the particle morphology which in turn needs be precisely characterized. Here we report investigation on the growth process of five-fold twinned Ag particles towards targeted morphology by using scanning electron microscopic imaging at variable incidence angles, in conjunction with 3D modelling, so as to reveal the particle–substrate contact profile and to infer the growth mechanism. Five-fold twinned Ag particles were obtained at large yield on SiO2/Si(1 0 0), MgO(1 0 0) and LaAlO3(1 0 0) substrates. Results show that fivefold twinned Ag particles on SiO2/Si(1 0 0) substrate are usually fully developed, demonstrating higher symmetries ( I h or D 5 h ) and acute contact angles, while on MgO(1 0 0) and LaAlO3(1 0 0) substrates the particles are usually heavily truncated with a contact characterized by also some obtuse angles. Difference in morphology occurs in the secondary growth stage where Ag atom migration along the particle-substrate interface may or may not be allowed. A set of parameters including contacting facet/contact angles and the height-edge length ratio are proposed for the morphology description of the five-fold twinned particles on support. Our work has resolved the influential factors in determining the morphology of large metal particles from physical vapor deposition where continual growth of sessile particles landing on substrate plays a pivotal role. By manipulating the particle-substrate contact and the secondary growth stage, five-fold twinned metal particles with designed morphology can be prepared for specific applications.

Mapping the Seabed and Shallow Subsurface with Multi-Frequency Multibeam Echosounders

Multi-frequency multibeam backscatter (BS) has indicated, in particular for fine sediments, the potential for increasing the discrimination between different seabed environments. Fine sediments are expected to have a varying signal penetration within the frequency range of modern multibeam echosounders (MBESs). Therefore, it is unknown to what extent the multispectral MBES data represent the surface of the seabed or different parts of the subsurface. Here, the effect of signal penetration on the measured multi-frequency BS and bathymetry is investigated. To this end, two multi-frequency datasets (90 to 450 kHz) were acquired with an R2Sonic 2026 MBES, supported by ground-truthing, in the Vlietland Lake and Port of Rotterdam (The Netherlands). In addition, a model to simulate the MBES bathymetric measurements in a layered medium is developed. The measured bathymetry difference between the lowest (90 kHz) and highest frequency (450 kHz) in areas with muddy sediments reaches values up to 60 cm dependent on the location and incident angle. In spatial correspondence with the variation in the depth difference, the BS level at the lowest frequency varies by up to 15 dB for the muddy sediments while the BS at the highest frequency shows only small variations. A comparison of the acoustic results with the ground-truthing, geological setting and model indicates that the measured bathymetry and BS at the different frequencies correspond to different parts of the seabed. However, the low-frequency BS cannot be directly related to a subsurface layer because of a significant sound attenuation in the upper layer. The simulation of the MBES bottom detection indicates that the bathymetry measured at the highest and lowest frequency can be used to determine the thickness of thin layers (∼20 cm). However, with an increasing layer thickness, the bottom detection becomes more sensitive to the incident angle and small variations in the sediment properties. Consequently, an accurate determination of the layer thickness is hampered. Based on this study, it is highly recommended to analyze multi-frequency BS in combination with the inter-frequency bathymetry difference to ensure a correct interpretation and classification of multi-frequency BS data.

A 3D Hemispheric Steam Generator Based on An Organic–Inorganic Composite Light Absorber for Efficient Solar Evaporation and Desalination

AbstractSolar‐driven interfacial steam generation is emerging as a sustainable and environmental‐friendly technology for potential applications in sterilization, desalination, and wastewater treatment. Despite the impressive progress achieved at labs, only few designs specialize in ambient and outdoor applications. Herein, a 3D hemispheric steam generator composed of nanocarbon (CB):poly(methyl methacrylate) (PMMA) composite materials as a light‐absorber, which boosts the light absorption in a wide range of incident angles, is reported. Gratifyingly, the 3D hemispheric steam generator afford efficient water evaporation and high photothermal conversion efficiencies of ≈87% when employing moderate sunlight (0.75 sun) with varied incident angles (90°, 80°, and 65°) in a set of indoor measurements. The more hydrophobic surface of the light‐absorber enabled by PMMA leads to better durability and avoids significant salt accumulation for solar desalination. This work highlights the intriguing prospect of this novel 3D hemispheric design and elegant organic–inorganic composite concept to realize efficient clean water production for potential real‐world applications.

Polarization property of light scattered on dielectric nanorods at oblique incident angle

We report the study of light polarization property upon scattering off a dielectric nanorod in which the direction of the incident light is at an angle with respect to the cylinder main axis. The numerical work is done on the basis of the cylindrical Mie theory. It is shown that for incident light with different polarization, the resulted scattering cross-section spectra will also show different characteristics with varying incident angles. For TE case, resonance splitting is observed due to excitation of a new resonance mode, while for TM case, resonance merging is observed. An interference effect between different resonance modes due to variation of incident angle is then resulted in suppression of backward scattering intensity for TM case. Meanwhile, for TE case, at illumination angle approaching grazing angle, a spectral range exists whereby the scattered wave’s angular intensity profile forms a perpendicular dipolar feature with different polarization. The reported results may be useful for aplication of nanoantenna, photovoltaic, and polarization conversion.

Effects of laser processing conditions on wettability and proliferation of Saos-2 cells on CoCrMo alloy surfaces

Abstract Any processing disturbances in laser surface texturing (LST) could compromise the resulting surface topography and their desired functional response. Disturbances such as focal plane offsets and beam incident angle variations are always present in LST processing of 3D parts and can affect the surface morphology. In this research the effects of these laser processing disturbances in producing laser induced surface structures (LIPSS) on CoCrMo alloy substrates were investigated. In particular, these two disturbances were considered as laser processing variables to determine their effects on functional responses of LIPSS treated surfaces, i.e. surface wettability and the proliferation of Saos-2 osteoblast-like cells were evaluated. It was found that the changes of laser processing conditions led to a decrease in surface wettability and Saos-2 cells proliferation. In addition, a correlation between surface wettability and cell proliferation on LIPSS treated surface was identified and conclusions made about the effects of investigated process disturbances on the functional response of LIPSS treated CoCrMo substrates.

Large-Angle, Broadband, and Multifunctional Directive Waveguide Scatterer Gratings

Conventional surface-relief gratings are inefficient at deflecting normally incident light by large angles. This limits the overall efficiency of grating-based optical instruments and also restricts their use in many applications. Here, we demonstrate a simple approach for the design of diffraction gratings that can be highly efficient for large deflection angles, while also offering additional functionality. Such gratings are composed of a unit cell comprising a vertically oriented asymmetric slot waveguide. The unit cell shows oscillating unidirectional scattering behavior that can be precisely tuned as a function of the waveguide length. This occurs due to interference between multiple modes excited in the structure by the incident light. In contrast to metasurface-based gratings with multiple resonant subelements, a periodic arrangement of such nonresonant diffracting elements allows for broadband operation and a strong tolerance for variations in angle of incidence. Full-wave simulations show that our grating designs can exhibit diffraction efficiencies ranging from 94% for a deflection angle of 47° to 80% for a deflection angle of 80°. To show the multifunctionality of our approach, we also demonstrate a flat polarization beamsplitter and a polarization insensitive grating.

Multichannel filter application of a magnetized cold plasma defect in periodic structure of ZnS/TiO2 materials

In this article, transmission spectra of multilayer structure of zinc sulfide (ZnS) and titanium dioxide (TiO2) with defect of magnetized cold plasma (MCP) have been calculated theoretically by using characteristics transfer matrix method. The transmission spectra versus frequency have been analyzed for symmetric and asymmetric structure. Due to have a multiple band gaps in the asymmetric structure, we have taken the asymmetric structure for analysis with the parameters of MCP and the thicknesses of the dielectric materials. It is well known that magnetized cold plasma is an abnormal material because the permittivity changes with applied external magnetic field, and shows tunable photonic band gap for permittivity of the MCP. Now, the transmission spectra of the asymmetric structure versus frequency by inserting one or two magnetized cold plasma layer were analyzed with the variation of incident angles, the parameters of MCP, and the thicknesses of ZnS and TiO2 material. The analyzed transmission spectra of asymmetric structure with the variation of electron density, thicknesses of dielectric materials were obtained better results with defect of two plasma layers as compare to the defect of one layer of plasma. These obtained results reveal that the defect of two magnetized cold plasma layers of one dimensional asymmetric structure of ZnS, TiO2 may be used for the tunable multichannel filter at microwave region.

Experimental investigation of processing disturbances in laser surface patterning

Laser surface patterning has attracted a significant interest from industry and research due to its promising applications in surface functionalisation. However, there are specific issues and limitations associated with the beam delivery, especially when processing 3-D surfaces and/or setting up routines for executing complex multi-axis processing strategies. In particular, there are common processing disturbances that affect the resulting surface topographies and profiles and their respective functional responses, i.e. geometrical distortions of resulting surface patterns, focal offset distance (FOD) and variations of beam incident angle (BIA). A method to investigate the effects of these factors in laser patterning 3-D surfaces is presented in this research, especially how their effects can be analysed independently by conducting empirical studies on planar surfaces. A pilot implementation of the proposed methodology is reported for producing channel-like patterns on stainless steel plates with a super-hydrophobic functional response. The results are discussed in detail to show how the effects of processing disturbances on topographies, profiles and areal parameters together with the respective functional responses of patterned planar surfaces can be analysed and then used to set constraints in pre-processing 3-D surfaces for follow up laser patterning.

Unsteady Flow Loss Mechanism and Aerodynamic Improvement of Two-Stage Turbine under Pulsating Conditions

The developments of two-stage turbocharging and turbocompounding promote the application of the two-stage turbine system in internal combustion engines. Since the turbine suffers from the pulsating exhaust, the performance deteriorates significantly from steady conditions. In the paper, the pulsating flow losses in the two-stage turbine are analyzed and a control method is proposed to improve the turbine performance. ANSYS CFX, which is a commercial software for computational fluid dynamic, is applied to resolve the three-dimensional unsteady flow problem. The accuracy of the simulation method is verified by the experimental data from each turbine. Firstly, the impacts of pulse amplitudes on transient loss of each component of the two-stage turbine are studied. Then flow field analysis is carried out to understand details of the unsteady flows. It is found that the variation of incidence angle at the low-pressure turbine (LPT) rotor tip is significantly larger than that at rotor hub, which causes severe flow loss near leading edge. As a result, the LPT performance drops down significantly. To improve the LPT performance, the blade shape at tip is modified. The aerodynamic performances of turbines with three different shapes under high- and low-load pulsating flow conditions are evaluated. It is found that increased inlet blade angle and medium thickness achieves good aerodynamic performance. The rotor averaged efficiency is improved by 2.27% under high-load pulsating condition.

Influence of angle of incidence, temperature and SiC content on erosive wear behavior of ZrB2‐SiC composites

AbstractThis research work deals with the investigation of erosive wear of spark plasma sintered ZrB2‐SiC composites with variation in angle of incidence (30°, 60°, and 90°), test temperature (room and 800°C) and SiC content (10, 20, and 30 vol.%). Results indicate a large variation in erosion rate from 2.13 to 75.45 mm3/kg with change in angle of incidence, test temperature, and SiC content. Erosion rate decreased with the decrease in angle of incidence, increase in temperature, and increase in SiC content. With increase in SiC content from 10 to 30 vol.%, a maximum reduction of 68% in erosion rate obtained at shallow incidence and room temperature, and a maximum reduction of 78% in erosion rate obtained at shallow incidence and 800°C. SEM‐EDS and XRD analyses indicate that formation of B2O3 and SiO2‐rich protective surface is responsible for high temperature erosion resistance of ZrB2‐SiC composites.

A Systematic Transmission Line Model for the Analysis of Self-Resonant Structures Within Multi-Layer Dielectric Media

This paper introduces a transmission line model analysis for dielectric-loaded self-resonant structures (SRSs). Equivalent circuit models, besides their fast computational time, usually offer some insights into the underlying physics of the electromagnetic structures, hence simplifying and improving the design and optimization criteria of these structures. A systematic approach for deriving impedance expressions of SRS on and within multi-layer dielectric media is presented. The process of extracting equivalent circuit parameters from impedance expressions is explained. The trends of equivalent circuit parameters are studied with different dielectric medium properties and various angles of incidence for an SRS with multiple resonant states highlighting the effect of changing the physical and electrical dimensions on the equivalent circuit parameters. The transmission line model responses are compared to full-wave simulation results, and model accuracy is assessed using the mean absolute error criteria. Furthermore, a new simplified method for calculating the forward transmission coefficient of an SRS within multi-layer media is proposed. This expression offers fundamental insights into the factors contributing to the $S_{21}$ response. Finally, experimental measurements for SRS embedded in a multi-layer dielectric media inside a waveguide is conducted and compared to the equivalent model with very good agreement.

A Dual Band Symmetric E-Shaped Split Ring Metamaterial Absorber For RF Energy Harvesting

In this paper, a new metamaterial absorber which comprises of a symmetrically E shaped split ring resonator patches at the top of the FR4 substrate of height 1.6mm for RF Energy Harvesting is proposed. The proposed design provides two absorption peak one at 5.8GHz with a maximum absorption of about 99% and other at 7.8GHz with a maximum absorption of about 92%. The absorption mechanism is investigated for the proposed metamaterial absorber. Also the polarization behavior of the absorber is also analyzed under various angles of incidence. The absorber has been tuned in such a way to have good broadband response in the UWB range.

Numerical Study of Savonius Wind Turbine Rotor with Elliptic Angle Shape Variation

The Savonius wind turbine uses a half-cylinder blade which is often called a bucket assembled so that the cross-section forms an S. This turbine is seen in the form of a half-cylinder consisting of a concave side and a convex side. This turbine is one type of Vertical Axis Wind Turbine (VAWT) that uses the difference in drag forces between the two buckets to be able to rotate the rotor. Therefore this rotor has the ability to self-start, which other wind turbines do not have, even so, the performance of the turbine. Savonius wind is still relatively low, so that it cannot be applied until now. Many studies have been carried out to improve performance, some of which include adding shielding, end plates, changing the shape of the blades, gap overlap, and others. The analysis in this numerical study included a comparison of the performance of conventional Savonius wind turbines and elliptic Savonius wind turbines with an assumed steady flow 2D flow and using turbulent viscous transitions k-kL-ω and k-ω SST with variations in flow velocity and angle of incidence of flow to the position of the rotor of the Savonius turbine. This results evaluated were the static torque coefficient with respect to the rotor position, the pressure distribution along the blade surface, and the wind flow characteristics near the rotor. The results of this study indicated that the modified wind turbine rotor had a higher static torque coefficient at low speeds. The two types of turbine rotors had relatively the same self-starting capability at high speeds.

Detection and Discrimination of Islanding and Faults in distribution system with Distributed Generation by using Wavelet based Alienation approach

This paper presents a wavelet transform based alienation technique for the protection of a radial 5 bus distribution system integrated with four wind type doubly fed Induction generators (DFIG).This technique is used to detect islanding condition and faults, classification of faults and their discrimination. Islanding is simulated at point of common coupling (PCC) and faults are simulated at each DG bus of the network. Daubechies wavelet transform has been used to decompose the current signals to get approximate coefficients. The Alienation coefficients of these approximate decompositions are termed as islanding and fault indexes. These indexes have been compared with predetermined threshold to detect islanding and faults. The same threshold value is utilized to discriminate transients associated with islanding and fault. Alienation coefficients at each bus over a half cycle window clearly detect both islanding and fault. Testing of the proposed algorithm has been carried out for various angles of incidence. Hence, the proposed algorithm is more effective and successful for finding the islanding condition as well as faults in distribution system with distributed generation.

Detection and Discrimination of Islanding and Faults in distribution system with Distributed Generation by using Wavelet based Alienation approach

This paper presents a wavelet transform based alienation technique for the protection of a radial 5 bus distribution system integrated with four wind type doubly fed Induction generators (DFIG).This technique is used to detect islanding condition and faults, classification of faults and their discrimination. Islanding is simulated at point of common coupling (PCC) and faults are simulated at each DG bus of the network. Daubechies wavelet transform has been used to decompose the current signals to get approximate coefficients. The Alienation coefficients of these approximate decompositions are termed as islanding and fault indexes. These indexes have been compared with predetermined threshold to detect islanding and faults. The same threshold value is utilized to discriminate transients associated with islanding and fault. Alienation coefficients at each bus over a half cycle window clearly detect both islanding and fault. Testing of the proposed algorithm has been carried out for various angles of incidence. Hence, the proposed algorithm is more effective and successful for finding the islanding condition as well as faults in distribution system with distributed generation.

One-dimensional photonic crystal for Bloch surface waves and radiation modes-based sensing

We report on a one-dimensional photonic crystal (1DPhC) represented by a multilayer structure used for a surface plasmon-like sensing based on Bloch surface waves and radiation modes employing a structure comprising a glass substrate and four bilayers of TiO 2/SiO 2 with a termination layer of TiO 2. We model the reflectance responses in the Kretschmann configuration with a coupling prism made of BK7 glass and express the reflectances for both (s and p) polarizations in the spectral domain for various angles of incidence to show that a sharp dip associated with the Bloch surface wave (BSW) excitation is obtained in p polarization when an external medium (analyte) is air. For s-polarized wave BSW is not excited and a shallow dip associated with the guided mode excitation is obtained for a liquid analyte (water). For decreasing angle of incidence, the dip depth is substantially increased, and resonance thus obtained is comparable in magnitude with resonance commonly exhibited by SPR-based sensors. In addition, we revealed that the resonances in s-polarization are obtained for other analytes. The surface plasmon-like sensing concept was verified experimentally in the Kretschmann configuration for the guided mode transformed into the radiation mode with a negative and constant sensitivity of −169 nm/RIU, and a detection limit of 5.9 ×10−5 RIU.

Numerical investigation of flow mechanisms of tandem impeller inside a centrifugal compressor

This study numerically investigated a single stage centrifugal compressor ‘‘Radiver’’ with a wedge diffuser and several tandem-designed impellers to explore the flow phenomena within the tandem impeller and the potential to enhance compressor performance. The results demonstrate that tandem design and clocking fraction (λs) significantly affects the compressor performance. The compressor stage with tandem impellers of Series A of boundary layer growth interruption alone are observed to have a widely operating range but efficiency and total pressure ratio penalty compared with that of conventional impeller. The tandem impeller with at least the same impeller efficiency as the conventional design is considered as a critical design criteria so that further modification process based on the flow characteristic of tandem impeller is necessary. In order to restrain the inducer wake and exducer shock losses, parameters modification of blade angle and thickness distributions are necessary and the modified tandem impeller of Series B is obtained. The modified tandem impeller with 25% clocking arrangement shows an 8.45% stall margin increase and maintains the total pressure ratio and efficiency as the conventional design, which proves the potential of tandem impeller to improve compressor stage performance. It is noteworthy that the tandem impellers of Radiver have not shown obviously balanced exit flow field and the fundamental mechanism of stall margin extending of tandem impeller lies on the improved impeller/diffuser matching performance resulting from the incidence angle variation at diffuser inlet.

Future gamma-ray missions’ polarimetric prospects

High-energy astrophysics polarimetry may significantly benefit from e-ASTROGAM and from AMEGO mission proposals, since to date limited polarimetric measurements were performed in this domain, exclusively under 1 MeV. The polarimetric potential of both missions was analyzed in the Compton regime by Monte Carlo mass model simulations with MEGAlib toolkit. The performance of e-ASTROGAM was analyzed by simulating Si tracker and calorimeter alternative configurations and detection materials, within missions’ volume, mass and power margins. The modulation polarimetric factor, Q, and the MDP were calculated for different polarized source types and for variable incidence angle measurement conditions. Finally, the polarimetric performances of both instruments was compared and analyzed. Q modulation factors obtained ranged between ~0.2 and ~0.4 in the 0.2–2.0 MeV band and MDP ~0.65% was estimated for a 100% polarized Crab type source, 1 Ms. observation time and 3σ significance.

Effect of obliquity of incident light on the performance of silicon solar cells

The aim of this work is to investigate the effect of angle of incident light on the performance of silicon solar cell. In this regard, numerical calculations have been performed to obtain the reflectance for double layer antireflection coating (DLARC) of Si3N4 at various angles of incidence (i.e.0o,15o,30o,45o,and60o) using transfer matrix method. Reflectances obtained, are found to increases with increase in angle of incidence. Calculated reflectances have been further used in the PC1D simulator as external reflectance files to study the performance of silicon solar cell. As a result of the simulation, the conversion efficiency (and short circuit current) of solar cell is found to decrease by 1.7% (0.062 mA/cm2) with increase in angle of incidence from 0oto60o.