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What Is A Dielectric Constant How Does Water Have A Dielectric Constant
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Pdf] The Dielectric Constant Of Water And Debye‐hückel Limiting Law Slopes
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Chang-Hwan Park Chang-Hwan Park Skillet Printers dot. Google Scholar ,,,, Preprints.org Google Scholar 1 |
Received: 7 May 2017 / Revised: 9 July 2017 / Accepted: 11 July 2017 / Published: 15 July 2017
Temperature Dependent Static Dielectric Constant Data Of Water For…
Microwave remote sensing techniques are used, among other things, for temporal and spatial observations of land properties, such as agricultural production and water management, and to improve the performance of numerical weather predictions and climate modeling using soils. Moisture data In this context, the effective dielectric constant of soils is a key variable for quantifying soil surface properties. We propose a new approach to the effective dielectric constant of a multiphase soil, which is based on the arithmetic average of the dielectric constant of the soil surface components. On average, it shows better agreement with experimental data than previous methods. In addition, the proposed new model overcomes the theoretical limitations of previous models by incorporating non-physical parameters to experimentally simulate measured data with satisfactory accuracy. For microwave remote sensing such as SMAP (passive soil moisture), SMOS (soil moisture and ocean salinity), and AMSR-E (Advanced Scanning Microwave Radiometer for EOS), the physical model showed 23–35% RMSE (root) in our study. root mean square error) compared to the most common reactant mixture models in predicting permittivity for real and imaginary parts, respectively. Also, in the radio band used in portable ground sensors such as TDR (Time Domain Reflectometer) and GRP (Ground Color Radar), the new dielectric mixture model reduced the RMSE to 53% when predicting the dielectric constant. We found that permittivity above the saturation point (dry soil porosity) has a clear and distinct pattern compared to that measured under unsaturated conditions. However, in our study, this pattern follows from the same mixing rule that applies to the mathematically dissociated state. It is hoped that the new dielectric mixing model will help improve the accuracy of satellite flood monitoring.
Unlike radiation in the visible and IR regions of the spectrum, microwaves generally penetrate through deep clouds without deposition and into the gaseous atmosphere (except in the microwave region, where some of the gas is absorbed). Thus, microwaves provide reliable information on soil quality and land surface temperature, as well as vegetation regardless of cloud cover. In addition, microwave remote sensing data allow us to reduce the uncertainty of remote sensing observations at other wavelengths, including over land, to improve estimates of atmospheric trace gases, aerosols, and clouds. In summary, understanding microwave interaction is important not only for remote sensing of land, but also for monitoring Earth systems.
In modern microwave remote sensing of space [1] several bands are used: L-band (1-2 GHz), C-band (4-8 GHz), X-band (8-12 GHz) and K-band (12 -40 GHz) accurate calculation of the effective permittivity is necessary for both passive and active microwave sensors. Furthermore, it is also important for material analysis in materials science. The first dielectric mixing formulas were proposed for cavities such as (hypothetical) spheres [3, 4], monodisperse spheres [5], polydisperse spheres [6], non-spheres [7], and also for non-spherical nanoporous media. and nanoparticles [8, 9]. However, these mixing models contain an inherent limitation for complex multiphase materials such as moist soils: the practical construction of dielectric mixing models based on microgeometry methods relies on empirical corrections. When a material is subjected to an electric field, its dielectric constant describes the interaction. Therefore, remote sensing of ground properties such as soil moisture requires a skilled operator to calculate the effective dielectric constant (Figure 1).
TDR (time-domain reflectometer) and GPR (ground-penetrating radar) measure reflectivity, calculate effective dielectric constant, and quantify soil water content using separately acquired information on soil temperature and texture. In contrast, airborne and spaceborne remote sensing instruments measure the brightness temperature of the TB (field A in Figure 1 ). To derive soil moisture from a measured tuber, traditional retrieval methods require additional information to account for soil temperature and texture, as well as the effects of vegetation. Vegetation has attempted to derive these supporting data from vegetation parameter b [ 10 ], multi-frequency microwave sensor measurements [ 11 , 12 , 13 ], NDVI (Normalized Differential Vegetation Index) [ 14 ] or MPDI (Microwave Polarization Difference Index). 15, 16, 17]. However, measurements of soil surface properties for bare soil without vegetation are already uncertain. Therefore, in this simple situation, auxiliary information on soil temperature and structure is important to determine soil moisture. Therefore, in this study we focus on bare soil The simulation results were confirmed by TDR measurements Future studies can extend the new dielectric mixing model presented here to the ground vegetation and canopy levels.
Experimental Investigation Of Dry Density Effects On Dielectric Properties Of Soil–water Mixtures With Different Specific Surface Areas
The dielectric mixing model presented here can be integrated into a land model All information needed to calculate TB is available in a soil surface model (such as soil temperature, soil moisture [18] and soil texture). Therefore, the new mixture model can be used in the operator to determine TB in the future. Present-day near-field soil moisture from passive microwave measurements. New “physically based” radiative transfer models [14, 16, 20] have been proposed for the search. They can be well combined with data assimilation [ 21 , 22 , 23 ], especially SM SMOS [ 24 , 25 ] and SMAP [ 26 , 27 ]. ] to estimate soil moisture in the root zone using . By combining our dielectric mixing model with the radiative transfer model, TB can be obtained more accurately in the microwave spectral region, which is useful not only for data assimilation schemes but also for field calibration and validation campaigns such as SMOSREX, useful or SMAPVEX [29 ].
This paper is organized as follows: in Section 2, we propose a new multiphase effective dielectric constant model; The attenuation coefficient and the dielectric constant of bound water are taken into account In Section 3, we apply the new model and compare the results with experimental data Finally, the discussion and conclusion of this study are given in Sections 4 and 5
Two communication theories have been proposed for terrestrial remote sensing, namely “dielectric averaging” proposed by Brown:
It is measured by TDR or GPR, related to the duration of electromagnetic wave propagation in our case in the soil-water mixture [32], according to:
Dielectric Constant Measurements Of Thin Films And Liquids Using Terahertz Metamaterials
Where c is the speed of light, t is the travel time along the probe rod, L is the length of the probe rod. form factor’:
The linear dependence of soil moisture on the refractive index, similar to equation (2), is widely used in calibration models [35, 36, 37, 38]. This method was further developed into different models based on power laws: since the estimation of soil moisture according to equation (2) could not satisfy the required accuracy for different soil textures and frequencies of electromagnetic waves, different values for α were proposed. , 34 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ] Furthermore, a nonlinear relationship between water content and dielectric constant has been proposed for experimental calibration models [ 47 , 48 , 49 ]. Figure 2 provides an overview of these models
