Huygens' Metasurface with Stable Transmission Response under Wide Range of Incidence Angle

This study deals with a local incidence angle correction method, i.e., the land cover-specific local incidence angle correction (LC-SLIAC), based on the linear relationship between the backscatter values and the local incidence angle (LIA) for a given land cover type in the monitored area. Using the combination of CORINE Land Cover and Hansen et al.’s Global Forest Change databases, a wide range of different LIAs for a specific forest type can be generated for each scene. The algorithm was developed and tested in the cloud-based platform Google Earth Engine (GEE) using Sentinel-1 open access data, Shuttle Radar Topography Mission (SRTM) digital elevation model, and CORINE Land Cover and Hansen et al.’s Global Forest Change databases. The developed method was created primarily for time-series analyses of forests in mountainous areas. LC-SLIAC was tested in 16 study areas over several protected areas in Central Europe. The results after correction by LC-SLIAC showed a reduction of variance and range of backscatter values. Statistically significant reduction in variance (of more than 40%) was achieved in areas with LIA range >50° and LIA interquartile range (IQR) >12°, while in areas with low LIA range and LIA IQR, the decrease in variance was very low and statistically not significant. Six case studies with different LIA ranges were further analyzed in pre- and post-correction time series. Time-series after the correction showed a reduced fluctuation of backscatter values caused by different LIAs in each acquisition path. This reduction was statistically significant (with up to 95% reduction of variance) in areas with a difference in LIA greater than or equal to 27°. LC-SLIAC is freely available on GitHub and GEE, making the method accessible to the wide remote sensing community.

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Multi-angle and nonuniform ground motions on cable-stayed bridges

Earthquake Spectra ◽

10.1177/87552930211051393 ◽

2021 ◽

pp. 875529302110513

Author(s):

Eleftheria Efthymiou ◽

Alfredo Camara

Keyword(s):

Seismic Response ◽

Ground Motion ◽

Seismic Waves ◽

Incidence Angle ◽

Design Parameters ◽

System Configuration ◽

Cable System ◽

Parametric Problem ◽

Wide Range ◽

Cable Stayed Bridges

The definition of the spatial variability of the ground motion (SVGM) is a complex and multi-parametric problem. Its effect on the seismic response of cable-stayed bridges is important, yet not entirely understood to date. This work examines the effect of the SVGM on the seismic response of cable-stayed bridges by means of the time delay of the ground motion at different supports, the loss of coherency of the seismic waves, and the incidence angle of the seismic waves. The focus herein is the effect of the SVGM on cable-stayed bridges with various configurations in terms of their length and of design parameters such as the pylon shape and the pylon–cable system configuration. The aim of this article is to provide general conclusions that are applicable to a wide range of canonical cable-stayed bridges and to contribute to the ongoing effort to interpret and predict the effect of the SVGM in long structures. This work shows that the effect of the SVGM on the seismic response of cable-stayed bridges varies depending on the pylon shape, height, and section dimensions; on the cable-system configuration; and on the response quantity of interest. Furthermore, the earthquake incidence angle defines whether the SVGM is important to the seismic response of the cable-stayed bridges. It is also confirmed that the SVGM excites vibration modes of the bridges that do not contribute to their seismic response when identical support motion is considered.

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Characterization of a loaded high impedance surface

International Journal of Microwave and Wireless Technologies ◽

10.1017/s1759078709990596 ◽

2009 ◽

Vol 1 (6) ◽

pp. 483-487 ◽

Cited By ~ 8

Author(s):

Fabrice Linot ◽

Xavier Begaud ◽

Michel Soiron ◽

Christian Renard ◽

Michèle Labeyrie

Keyword(s):

Incidence Angle ◽

Transverse Magnetic ◽

Impédance Surface ◽

Impedance Surface ◽

High Impedance ◽

At Resonance ◽

Wide Range ◽

Judicious Choice ◽

High Impedance Surface

A high impedance surface (HIS) consisting of metallic square patches electrically connected one to each other with resistors is shown. Tunability of the absorption factor is achieved by the resistor value. The absorbing band of the loaded HIS is determined by the phase of the signal reflected by this structure. The main contribution of the paper is to demonstrate the absorption behavior over a wide range of incidence angle for both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations. Using an equivalent circuit the resistor effect is investigated. It is shown that at resonance, the judicious choice of the resistor may lead to a significant absorption. The use of a waveguide simulator to characterize the performance of the loaded HIS is investigated. These methods have been used to design an ultra-thin absorber about λ8.4 GHz/35 thick.

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Ambiguities in AVO inversion of reflections from a gas‐sand

Geophysics ◽

10.1190/1.1443740 ◽

1995 ◽

Vol 60 (1) ◽

pp. 134-141 ◽

Cited By ~ 21

Author(s):

Giuseppe Drufuca ◽

Alfredo Mazzotti

Keyword(s):

Unique Solution ◽

Incidence Angle ◽

Synthetic Data ◽

Real Data ◽

Shear Velocity ◽

Sand Layer ◽

Borehole Data ◽

Starting Point ◽

Wide Range ◽

Compressional Velocity

We examine the reflections from a thick sand layer embedded in shales deposited in an open marine environment of Miocene age. Borehole data indicate that the sand bed is gas saturated. Making the assumptions of single interface reflections, plane‐wave propagation in elastic and isotropic media, and correct amplitude recovery of the actual seismic data, we try to invert the amplitude variation with offset (AVO) response for the compressional velocity [Formula: see text], shear velocity [Formula: see text], and density [Formula: see text] of the gas‐sand layer, knowing the parameters of the upper layer and the calibration constant. The actual reflections reach incidence angles up to 54 degrees at the farthest offset. Notwithstanding the large range of incidence angles, the outcomes of the inversion are ambiguous for we find many solutions that fit equally well, in a least‐squares sense, the observed AVO response. We present the locus of the solutions as curves in compressional velocity [Formula: see text], shear velocity [Formula: see text], and density [Formula: see text] space. To gain a better understanding of the results, we also perform the same inversion experiment on synthetic AVO data derived from the borehole information. We find that when inverting the AVO response in the same range of incidence angles as in the real data case, the exact solution is found whichever starting point we choose; that is, we have no ambiguity. However, if we limit the incidence angle range, e.g., to 15 degrees, the invention is no longer able to find a unique solution and the set of admissible solutions defines regular curves in [Formula: see text], [Formula: see text], [Formula: see text] space. We infer that residual noise in the recorded data is responsible for the ambiguities of the solutions, and that because of numerical noise, a wide range of incidence angle is required to obtain a unique solution even in noise‐free synthetic data.

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Characteristic analysis of the efficiency hill chart of Francis turbine for different water heads

Advances in Mechanical Engineering ◽

10.1177/1687814017690071 ◽

2017 ◽

Vol 9 (2) ◽

pp. 168781401769007 ◽

Cited By ~ 2

Author(s):

Pengcheng Guo ◽

Zhaoning Wang ◽

Longgang Sun ◽

Xingqi Luo

Keyword(s):

Incidence Angle ◽

Suction Side ◽

Francis Turbine ◽

Small Range ◽

Characteristic Analysis ◽

Wide Range ◽

Low Head ◽

Model Efficiency ◽

Hydraulic Turbines ◽

High Head

According to several model test results of Francis turbines, complete model efficiency hill charts were constructed. The formation and inevitability of diversified hydraulic phenomena on model efficiency hill chart for typical head range were analyzed and the difference is compared, as well as characteristics and commonness toward the curves are discussed and summarized. Furthermore, hydraulic performance and geometric features are presented by particularly analyzing the efficiency hill charts. The inherent characteristics of Francis turbine is expressed by all kinds of curves on the model efficiency hill charts, and these curves can be adjusted and moved in a small range but cannot be removed out. Due to wide range of unit speed in terms of medium-low-head hydraulic turbines, incipient cavitation curve on suction side can be observed and it is positioned close to the operation zone; however, it fails to be visualized for the high-head turbine. The blade channel vortex curves are in the vicinity of optimum region for low-head hydraulic turbines, while high-head shows reverse trend. The interaction between zero incidence angle and zero circulation curve has a significant influence on isoefficiency circles. All comparisons and analyses could provide hydraulic design basis and retrofit references.

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Electromagnetic tunneling through a three-layer asymmetric medium containing epsilon-negative slabs

Open Physics ◽

10.2478/s11534-013-0251-z ◽

2013 ◽

Vol 11 (5) ◽

Cited By ~ 3

Author(s):

Chao Yang ◽

Hui Zhao

Keyword(s):

Transfer Matrix ◽

Transfer Matrix Method ◽

Matrix Method ◽

Resonant Tunneling ◽

Incidence Angle ◽

Wide Range ◽

Tunneling Phenomenon

AbstractWith the transfer-matrix method, conditions of extraordinary electromagnetic resonant tunneling through all combinations of three-layer nonmagnetic (µr = 1) media containing epsilon-negative (ENG) and doublepositive (DPS) slabs were explored. We show that abnormal phenomena can occur in the ENG-DPS-ENG structure, without any restriction on the permittivity of the DPS layer. Changes of transmittance as a function of frequency and incidence angle for a dispersive, lossy model are also calculated, and the results demonstrate the possibility of exhibition this counterintuitive tunneling phenomenon in the DPS-ENG-DPS structure within a wide range of incidence angles.

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Part Load Behavior of the LP Part of an Industrial Gas Turbine

Volume 2A: Turbomachinery ◽

10.1115/gt2017-64778 ◽

2017 ◽

Author(s):

Milan V. Petrovic ◽

Alexander Wiedermann ◽

Srecko M. Nedeljkovic ◽

Milan Banjac

Keyword(s):

Flow Field ◽

Gas Turbine ◽

Incidence Angle ◽

Pressure Ratio ◽

Solution Procedure ◽

Turbine Efficiency ◽

Through Flow ◽

Wide Range ◽

Design Speed ◽

Industrial Gas Turbine

The operation under off-design conditions of a two-stage LP part of a 6.5 MW industrial gas turbine was analyzed in this work. Since the turbine is able to vary the rotation speed in a wide range from 40 to 140% of the design speed, a flow with extremely large positive and negative incidence angle appears. The flow field was calculated applying 2D through-flow code for the analysis of axial multistage turbines with cooling by air from compressor bleed. The code was developed by the authors and validated by calculation of a number of test cases with different configurations. The method is based on a stream function approach and a finite element solution procedure. In parallel, the flow in the turbine was calculated using a commercial CFD code. Based on the calculated flow field, the turbine efficiency and pressure ratio and also different stage parameters were determined for the design point and for a wide range of off-design conditions. Comparison of the predicted results and measured test data for a number of parameters showed good agreement.

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The Influences of Off-Design Incidence Angle and Discrete Hole Shapes on Film Cooling Effectiveness

Volume 4: Heat Transfer; Electric Power ◽

10.1115/86-gt-135 ◽

1986 ◽

Author(s):

Shao-Yen Ko ◽

Deng-Ying Liu ◽

Jian-Guo Jia ◽

Fu-Kang Tsou

Keyword(s):

Carbon Dioxide ◽

Film Cooling ◽

Convex Surface ◽

Incidence Angle ◽

Turbine Blades ◽

Cooling Effectiveness ◽

Film Cooling Effectiveness ◽

Pressure Surface ◽

Ejection Angle ◽

Wide Range

Detailed tests have been conducted in the cascade heat transfer wind tunnel in order to investigate film cooling effectiveness of single and double-row discrete holes on the leading edge of the pressure surface of a turbine blade. Mass transfer analogy has been used in this experiment. Carbon dioxide was added to the cooling air. The concentration distribution of the carbon dioxide downstream of the cooling film was measured by chromatograph. Two sets of testing blades with discrete holes of different shapes were used. The first set had round holes with diameter of 1.5 mm, and the ejection angle was 70°. The second set had rectangular holes with width of 1.0 mm and whose ratio of length to width was 5, the ejection angle being 90°. The holes between rows were arranged in staggered pattern. It was found that the incidence angle has strong influence on film cooling of turbine blades. The film cooling effectiveness near the ejection hole on the pressure surface (concave surface) is higher than that on a flat plate and on a suction surface (convex surface). Over a wide range of blowing ratio M, the film cooling effectiveness of rectangular hole is much higher than round holes.

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Response of Multi-Incidence Angle Polarimetric RADARSAT-2 Data to Herbaceous Vegetation Features in the Lower Paraná River Floodplain, Argentina

Remote Sensing ◽

10.3390/rs13132518 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2518

Author(s):

Natalia Soledad Morandeira ◽

Matías Ernesto Barber ◽

Francisco Matías Grings ◽

Frank Ahern ◽

Patricia Kandus ◽

...

Keyword(s):

Incidence Angle ◽

Paraná River ◽

Schoenoplectus Californicus ◽

Wetland Ecosystems ◽

River Floodplain ◽

Parana River ◽

Wide Range ◽

Paraná River Floodplain ◽

Maximum Likelihood Estimations ◽

Hydrological Monitoring

Wetland ecosystems play a key role in hydrological and biogeochemical cycles. In emergent vegetation targets, the occurrence of double-bounce scatter is indicative of the presence of water and can be valuable for hydrological monitoring. Double-bounce scatter would lead to an increase of σ0HH over σ0VV and a non-zero co-polarized phase difference (CPD). In the Lower Paraná River floodplain, a total of 11 full polarimetric RADARSAT-2 scenes from a wide range of incidence angles were acquired during a month. Flooded targets dominated by two herbaceous species were sampled: Schoenoplectus californicus (four sites, Bulrush marshes) and Ludwigia peruviana (three sites, Broadleaf marshes). As a general trend, σ0HH was higher than σ0VV, especially at the steeper incidence angles. By modeling CPD with maximum likelihood estimations, we found results consistent with double-bounce scatter in two Ludwigia plots, at certain scene incidence angles. Incidence angle accounted for most of the variation on σ0HH, whereas emergent green biomass was the main feature influencing σ0HV. Multivariate models explaining backscattering variation included the incidence angle and at least two of these variables: emergent plant height, stem diameter, number of green stems, and emergent green biomass. This study provides an example of using CPD to decide on the contribution of double-bounce scatter and highlights the influence of vegetation biomass on radar response. Even with the presence of water below vegetation, the contribution of double-bounce scatter to C-band backscattering depends on scene incidence angles and may be negligible in dense herbaceous targets.

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CFD Wind Tunnel Tests of Centrifugal Stage Return Channel Vane Cascades

ASME 2015 Gas Turbine India Conference ◽

10.1115/gtindia2015-1216 ◽

2015 ◽

Cited By ~ 4

Author(s):

Y. Galerkin ◽

L. Marenina ◽

K. Soldatova

Keyword(s):

Incidence Angle ◽

Flow Behavior ◽

Radial Component ◽

Loss Coefficient ◽

Centrifugal Stage ◽

Wide Range ◽

Low Specific Speed ◽

Specific Speed ◽

Return Channel ◽

Object Of Study

Stator part of a centrifugal compressor stage is a proper object of study by CFD calculations meaning better understanding of flow behavior, checking of field type design methods and possible improvements. Several stators with vane and vaneless diffusers for stages with different specific speed were designed by standard methodology and numerically analyzed. Results were verified. Calculation in a whole has demonstrated validity of existing recommendation. The specific velocity for stators is introduced which can be applied to match an impeller and a stator. Calculations demonstrated quick efficiency drop for stators with specific speed less than 0,215. Return channel vane cascades were studied in wide range of solidity with constant vane height and with constant radial component of velocity. Empirical formulae with non-dimensional circulation as an argument are proposed for loss coefficient, profile loss coefficient, optimal incidence angle and exit lag angle. Candidates of the low specific speed stator have demonstrated that an arbitrary channels’ wideness to diminish friction losses is not effective. Better flow organization is preferable. Modification of a crossover demonstrated positive results for high and low specific speed stators.

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