Use Of Reflectometry Research Articles

A Semiempirical Modeling of Soil Moisture, Vegetation, and Surface Roughness Impact on CYGNSS Reflectometry Data

Data from the Cyclone Global Navigation Satellite System (CYGNSS) mission augmented with a physical surface scattering model were analyzed to develop a semiempirical model, which consists of three main modeling components for soil moisture, vegetation, and surface roughness. CYGNSS data collected from March 2017 to March 2020 were collocated with the soil moisture data from the Soil Moisture Active Passive (SMAP) mission and climatology vegetation water content (VWC) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data. The matchup data were binned as a function of soil moisture, VWC, and incidence angle. The CYGNSS data were calibrated using a coherent reflection equation to obtain an effective reflectivity. The response of CYGNSS effective reflectivity to soil moisture changes is consistent with the change of the Fresnel reflectivity based on Mironov’s soil dielectric constant model used by the SMAP and Soil Moisture Ocean Salinity (SMOS) missions for soil moisture retrieval. The CYGNSS effective reflectivity decreases approximately linearly (in dB) with respect to the NDVI-VWC. The estimated values of vegetation attenuation parameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$b$ </tex-math></inline-formula> ) agree with values published in the literature and are corroborated with the estimated values of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$b$ </tex-math></inline-formula> using the SMAP dual-polarized channel algorithm based on land cover types. A CYGNSS surface scattering map has been derived and reveals a mixed contribution of coherent and incoherent scattering effects and the effects of topography. The semiempirical model, leveraging two of the key modeling functions used by microwave radiometry, will pave the way for a synergistic use of reflectometry and radiometry data for multiparameter retrieval and development of consistent soil moisture products.

Aplicação da reflectometria na identificação de cargas elétricas similares: uma análise bibliométrica

A energia é um bem essencial para o desenvolvimento, e seu uso racional é necessário para minimizar os impactos e custos ambientais. O monitoramento de carga tem um papel muito importante nesse contexto, pois é necessário saber quais dispositivos estão consumindo a energia elétrica, quanto, e em que momento ela é consumida. O objetivo deste artigo é o de realizar uma pesquisa bibliométrica para análise qualitativa e quantitativa sobre a identificação de cargas, especialmente as altamente similares, inclusive através do uso da reflectometria nesse processo. Nas análises feitas neste trabalho, constata-se que a China é o país com o maior número de publicações, seguido pelos Estados Unidos. Observa-se ainda um recente aumento nas publicações sobre identificação de carga, demonstrando que o tema tem ganhado cada vez mais relevância no cenário mundial.

Upgrade of the COMPASS tokamak microwave reflectometry system with I/Q modulation and detection

The microwave reflectometry system on COMPASS tokamak uses the frequency modulated continuous wave (FM-CW) in the K and Ka bands. The fast swept synthesizer together with the homodyne detection provides the complex beat frequency spectrum for the density profile reconstruction. The homodyne detection limits the use of reflectometry in the other applications like correlation or Doppler reflectometry. Our effort was to implement a heterodyne detection based on the existing system. We have decided to use a single-sideband modulator (SSBM) scheme to keep the compatibility with the fast sweeping. Lack of suitable SSBMs on the market leads us to use I/Q modulator, which is modulated by the in-quadrature signals.

Performance of the microwave reflectometry diagnostic for density profile measurements on ASDEX Upgrade

The broadband reflectometry system on ASDEX Upgrade is now routinely providing electron density profiles with a minimum temporal spacing of 30 μs. The plasma is probed from zero density to ne=6.64×1019 m−3 at the low field side with combined O and X modes, and from ne=0.318×1019 to ne=6.64×1019 m−3 at the high field side using O mode. Here we analyze the performance of the diagnostic for profile measurements taking into account its design options and the experimental results obtained in a wide range of plasma regimes. We address several questions, in particular the measuring range of the antennas and the range of density gradients. It is shown that it is possible to obtain a detailed evolution of the density profile and density gradient even in the presence of turbulence, providing that sufficient data can be extracted from the plasma. The radial movements of the plasma can be measured with great accuracy, which is especially important for the use of reflectometry for plasma position control, as is proposed for the International Thermonuclear Experimental Reactor. The experimental results demonstrate that the frequency modulation of a continuous wave reflectometry system on ASDEX Upgrade can provide reliable and accurate density profile measurements at both sides of the plasma with automatic analysis.

Theoretical aspects of the use of pulsed reflectometry in a spheromak plasma

Pulsed reflectometry using both ordinary (O) and extraordinary (X) modes has the potential of providing time- and space-resolved measurements of the electron density, the magnitude of the magnetic field, and the magnetic shear as a function of radius. Such a diagnostic also yields the current profile from the curl of the magnetic field. This research addresses theoretical issues associated with the use of reflectometry in the Sustained Spheromak Physics Experiment spheromak experiment at the Lawrence Livermore National Laboratory. We have extended a reflectometry simulation model to accommodate O- and X-mode mixed polarization and linear mode conversion between the two polarizations. A Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) formula for linear mode conversion agrees reasonably well with direct numerical solutions of the wave equation, and we have reconstructed the magnetic pitch–angle profile by matching the results of the WKBJ formula with the mode conversion data observed in simulations using a least-squares determination of coefficients in trial functions for the profile. The reflectometry data also yield information on fluctuations. Instrumental issues, e.g., the effects of microwave mixers and filters on model reflectometry pulses, have been examined to optimize the performance of the reflectometry diagnostics.

The use of reflectometry for the study of swelling of latex particles at a silica surface

The use of reflectometry for the study of swelling of latex particles at a silica surface

Use of reflectometry for determination of nitrate‐nitrogen in well water

Abstract Recurrent monitoring of water wells is necessary to ensure that nitrate‐nitrogen (NO3‐N) concentrations in groundwater do not exceed 10 mg/L, the maximum contaminant level set by the U.S. Environmental Protection Agency. Continuous chemical analysis is often a time consuming and expensive process. A recently developed ‘Reflectoquant Analysis System’, which employs reflectometry techniques, may offer a simple and accurate method for NO3‐N analysis. The objective of this study was to evaluate the ‘Reflectoquant Analysis System’ as an alternative method for determination of NO3‐N in well water. Water samples were collected from 42 wells in Oklahoma. The samples were analyzed using the ‘Reflectoquant Analysis System’, automated cadmium reduction (Griess‐Ilosvay), ion chromatography, and phenoldisulfonic acid procedures. The linear range of the ‘Reflectoquant Analysis System’ is 1.1 to 50.6 mg/L NO3‐N. Samples exceeding this range must be diluted before analysis is performed. Excluding two wells where...

Recent developments in microwave reflectometry at JET (invited)

The latest developments in microwave reflectometry work at JET are described. A multichannel reflectometer system which can measure either the spatial profile of the electron density, or the propagation of rapid density perturbations, is described and some illustrative results are presented. The possible use of reflectometry as a technique for determining the total internal magnetic field is discussed and the results of an experiment to test the basis of this method are presented. Finally, a new technique, correlation reflectometry, which has been developed specifically for studying density fluctuations is described and some preliminary results are presented.

Mechanical characterization by acoustic techniques of SiC chemical-vapour-deposited thin films

Study of the propagation of acoustic waves in ceramic materials is difficult because of their high velocities. It is even harder when materials are processed in thin layers. The conjoint use of reflectometry and acoustic microscopy allows the obtention of shear and longitudinal wave velocities of SiC chemical-vapour-deposited thin films with good reliability. These values can then give access to the elastic constants E, G and v of the materials considered on the basis of homogeneous and isotropic solid theory.

Rectangular waveguide characterization for reflectometry

Simple first-order correction formulas are developed to describe the combined effect of wall distortion and wall loss on the propagation constant and normalized impedance of nominally rectangular waveguides intended for use in reflectometry. A simple method of measuring the propagation constant at a single frequency is described, resulting in practical advantages in characterization of the waveguide at other frequencies. >