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Special Issue "Selected Papers from ISEMA 2018"

A special issue of Sensors (ISSN 1424-8220).

Deadline for manuscript submissions: closed (21 April 2019)

Special Issue Editors

Guest Editor
Prof. Wojciech Skierucha

Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland
Website | E-Mail
Phone: +48 81 7445061
Interests: dielectric spectroscopy; dielectric aquametry; environmental monitoring; dielectric indexes of food quality; non-destructive sensing; irrigation management; soil moisture sensing terrestrial and undeground networks
Guest Editor
Dr. Agnieszka Szypłowska

Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland
Website | E-Mail
Interests: dielectric properties of soil; measurement of soil moisture and salinity; FDR; dielectric models; microwave measurement methods
Guest Editor
Dr. Andrzej Wilczek

Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland
Website | E-Mail
Interests: dielectric spectroscopy; dielectric aquametry; TDR; TDT; dielectric sensors development; HF electromagnetic simulations

Special Issue Information

Dear Colleagues,

The 12th International Conference on Electromagnetic Wave Interaction with Water and Moist Substances—ISEMA 2018—will take place in Lublin, Poland, 4–7 June 2018, and is organized this time by the Institute of Agrophysics, Polish Academy of Sciences and Foundation of the Polish Academy of Sciences.

 The conference will provide an interdisciplinary platform for sharing experience and discussing latest scientific results in understanding, development and application of electromagnetic moisture measurement techniques.

Conference Topics

  • Electromagnetic determination of physical properties of materials and standardization of measuring methods.
  • Moisture content determination and monitoring in soil, snow, agricultural materials, waste disposals and other nonhomogeneous materials.
  • Progress in measurement instrumentation and methods of broadband dielectric spectroscopy.
  • Electromagnetic sensors in time- and frequency-domain for moisture content determination.
  • Theory and applications of electromagnetic mixing rules and formulas.
  • Dielectric relaxation properties of water in heterogeneous materials, including biological substances and tissues.
  • Applications of broadband dielectric spectroscopy in precision agriculture, civil engineering, industry, etc.
  • Remote sensing for Earth’s water monitoring.
  • Computational methods of electromagnetic wave propagation in dispersive and lossy dielectrics.
  • Integrated techniques using RF and/or microwave dielectric measurements with other methods such as impedance spectroscopy, THz spectroscopy, Raman spectroscopy, infrared spectroscopy, NMR, etc.

Prof. Wojciech Skierucha
Dr. Agnieszka Szypłowska
Dr. Andrzej Wilczek
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Dielectric spectroscopy
  • Soil moisture
  • Soil salinity
  • Microwave moisture measurements
  • Dielectric properties of materials
  • Remote sensing
  • Electromagnetic moisture sensors
  • Dielectric sensors
  • TDR
  • FDR
  • Dielectric mixing rules
  • Moisture monitoring

Published Papers (6 papers)

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Research

Open AccessArticle Combined Thickness and Permittivity Measurement of Thin Layers with Open-Ended Coaxial Probes
Sensors 2019, 19(8), 1765; https://doi.org/10.3390/s19081765
Received: 25 February 2019 / Revised: 9 April 2019 / Accepted: 11 April 2019 / Published: 12 April 2019
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Abstract
This paper presents a method to simultaneously determine the thickness and permittivity of thin layers from multi-frequency reflection coefficient measurements using an open-ended coaxial probe. This is achieved by exploiting that the probe becomes radiating at frequencies higher than the probe’s typical operating [...] Read more.
This paper presents a method to simultaneously determine the thickness and permittivity of thin layers from multi-frequency reflection coefficient measurements using an open-ended coaxial probe. This is achieved by exploiting that the probe becomes radiating at frequencies higher than the probe’s typical operating range. Permittivity information is extracted from measurements in the typical frequency range, whereas thickness information is obtained from high frequency measurements by exploiting resonances that occur when the radiated waves are reflected at the layer boundary. A finite element model of the measurement set-up is made in COMSOL MultiphysicsTM, and a matrix of simulations spanning the relevant layer thicknesses and permittivity range is generated. The measured permittivity spectra of unknown samples are compared to the simulation matrix to estimate layer thickness and permittivity. The method is verified by measurements of water–ethanol mixtures. An application example where the water fraction and layer thickness of a gas hydrate deposition layer is estimated from permittivity measurements in a multiphase flow loop is also presented. Full article
(This article belongs to the Special Issue Selected Papers from ISEMA 2018)
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Open AccessArticle A Seven-Rod Dielectric Sensor for Determination of Soil Moisture in Well-Defined Sample Volumes
Sensors 2019, 19(7), 1646; https://doi.org/10.3390/s19071646
Received: 13 March 2019 / Revised: 2 April 2019 / Accepted: 3 April 2019 / Published: 6 April 2019
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Abstract
This paper presents a novel seven-rod sensor used for time-domain reflectometry (TDR) and frequency-domain reflectometry (FDR) measurements of soil water content in a well-defined sample volume. The probe directly measures the complex dielectric permittivity spectrum and for this purpose requires three calibration media: [...] Read more.
This paper presents a novel seven-rod sensor used for time-domain reflectometry (TDR) and frequency-domain reflectometry (FDR) measurements of soil water content in a well-defined sample volume. The probe directly measures the complex dielectric permittivity spectrum and for this purpose requires three calibration media: air, water, and ethanol. Firstly, electromagnetic simulations were used to study the influence of the diameter of a container on the sensitivity zone of the probe with respect to the measured calibration media and isopropanol as a verification liquid. Next, the probe was tested in three soils—sandy loam and two silt loams—with six water contents from air-dry to saturation. The conversion from S 11 parameters to complex dielectric permittivity from vector network analyzer (VNA) measurements was obtained using an open-ended liquid procedure. The simulation and measurement results for the real part of the isopropanol dielectric permittivity obtained from four containers with different diameters were in good agreement with literature data up to 200 MHz. The real part of the dielectric permittivity was extracted and related to the moisture of the tested soil samples. Relations between the volumetric water content and the real part of the dielectric permittivity (by FDR) and apparent dielectric permittivity (by TDR) were compared with Topp’s equation. It was concluded that the best fit to Topp’s equation was observed in the case of a sandy loam. Data calculated according to the equation proposed by Malicki, Plagge, and Roth gave results closer to Topp’s calibration. The obtained results indicated that the seven-rod probe can be used to accurately measure of the dielectric permittivity spectrum in a well-defined sample volume of about 8 cm3 in the frequency range from 20 MHz to 200 MHz. Full article
(This article belongs to the Special Issue Selected Papers from ISEMA 2018)
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Open AccessArticle Dielectric Spectroscopy Using Dual Reflection Analysis of TDR Signals
Sensors 2019, 19(6), 1299; https://doi.org/10.3390/s19061299
Received: 26 February 2019 / Revised: 8 March 2019 / Accepted: 12 March 2019 / Published: 14 March 2019
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Abstract
Time-domain reflectometry (TDR) has been a powerful tool for measuring soil dielectric properties. Initiating from apparent dielectric constant (Ka) measurement up until apparent and complex dielectric spectroscopies, the embedded information in the TDR signal can be extracted to inspire our [...] Read more.
Time-domain reflectometry (TDR) has been a powerful tool for measuring soil dielectric properties. Initiating from apparent dielectric constant ( K a ) measurement up until apparent and complex dielectric spectroscopies, the embedded information in the TDR signal can be extracted to inspire our understanding of the underlying dielectric behaviors. Multiple full waveform inversion techniques have been developed to extract complex dielectric permittivity (CDP) spectrum, but most of them involved prior knowledge of input function and tedious calibration. This rendered the field dielectric spectroscopy challenging and expensive to conduct. Dual reflection analysis (DRA) is proposed in this study to measure CDP spectrum from 10 MHz to 1 GHz. DRA is a simple, robust, model-free, and source-function free algorithm which requires minimal calibration effort. The theoretical framework of DRA is established and the necessary signal processing procedures are elaborated in this study. Eight materials with different dielectric characteristics are selected to evaluate DRA’s performance, by using both simulated and experimental signals. DRA is capable of measuring non-dispersive materials very well, whereas dispersive materials require the assistance of a long-time-window (LTW) extraction method to further extend the effective bandwidth. The DRA approach is suitable for field applications that can only record a limited amount of data points and in-situ dielectric spectroscopy. Full article
(This article belongs to the Special Issue Selected Papers from ISEMA 2018)
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Open AccessArticle Determination of the Porosity Distribution during an Erosion Test Using a Coaxial Line Cell
Sensors 2019, 19(3), 611; https://doi.org/10.3390/s19030611
Received: 6 December 2018 / Revised: 24 January 2019 / Accepted: 29 January 2019 / Published: 1 February 2019
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Abstract
The detection of porosity changes within a soil matrix caused by internal erosion is beneficial for a better understanding of the mechanisms that induce and maintain the erosion process. In this paper, an electromagnetic approach using Spatial Time Domain Reflectometry (STDR) and a [...] Read more.
The detection of porosity changes within a soil matrix caused by internal erosion is beneficial for a better understanding of the mechanisms that induce and maintain the erosion process. In this paper, an electromagnetic approach using Spatial Time Domain Reflectometry (STDR) and a transmission line model is proposed for this purpose. An original experimental setup consisting of a coaxial cell which acts as an electromagnetic waveguide was developed. It is connected to a transmitter/receiver device both measuring the transmitted and corresponding reflected electromagnetic pulses at the cell entrance. A gradient optimization method based on a computational model for simulating the wave propagation in a transmission line is applied in order to reconstruct the spatial distribution of the soil dielectric permittivity along the cell based on the measured signals and an inversion algorithm. The spatial distribution of the soil porosity is deduced from the dielectric permittivity profile by physically based mixing rules. Experiments were carried out with glass bead mixtures of known dielectric permittivity profiles and subsequently known spatial porosity distributions to validate and to optimize both, the proposed computational model and the inversion algorithm. Erosion experiments were carried out and porosity profiles determined with satisfying spatial resolution were obtained. The RMSE between measured and physically determined porosities varied among less than 3% to 6%. The measurement rate is sufficient to be able to capture the transient process of erosion in the experiments presented here. Full article
(This article belongs to the Special Issue Selected Papers from ISEMA 2018)
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Open AccessArticle Estimating Pore Water Electrical Conductivity of Sandy Soil from Time Domain Reflectometry Records Using a Time-Varying Dynamic Linear Model
Sensors 2018, 18(12), 4403; https://doi.org/10.3390/s18124403
Received: 8 November 2018 / Revised: 7 December 2018 / Accepted: 10 December 2018 / Published: 13 December 2018
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Abstract
Despite the importance of computing soil pore water electrical conductivity (σp) from soil bulk electrical conductivity (σb) in ecological and hydrological applications, a good method of doing so remains elusive. The Hilhorst concept offers a theoretical model [...] Read more.
Despite the importance of computing soil pore water electrical conductivity (σp) from soil bulk electrical conductivity (σb) in ecological and hydrological applications, a good method of doing so remains elusive. The Hilhorst concept offers a theoretical model describing a linear relationship between σb, and relative dielectric permittivity (εb) in moist soil. The reciprocal of pore water electrical conductivity (1/σp) appears as a slope of the Hilhorst model and the ordinary least squares (OLS) of this linear relationship yields a single estimate ( 1 / σ p ^ ) of the regression parameter vector (σp) for the entire data. This study was carried out on a sandy soil under laboratory conditions. We used a time-varying dynamic linear model (DLM) and the Kalman filter (Kf) to estimate the evolution of σp over time. A time series of the relative dielectric permittivity (εb) and σb of the soil were measured using time domain reflectometry (TDR) at different depths in a soil column to transform the deterministic Hilhorst model into a stochastic model and evaluate the linear relationship between εb and σb in order to capture deterministic changes to (1/σp). Applying the Hilhorst model, strong positive autocorrelations between the residuals could be found. By using and modifying them to DLM, the observed and modeled data of εb obtain a much better match and the estimated evolution of σp converged to its true value. Moreover, the offset of this linear relation varies for each soil depth. Full article
(This article belongs to the Special Issue Selected Papers from ISEMA 2018)
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Open AccessArticle Spatial Retrieval of Broadband Dielectric Spectra
Sensors 2018, 18(9), 2780; https://doi.org/10.3390/s18092780
Received: 5 July 2018 / Revised: 9 August 2018 / Accepted: 16 August 2018 / Published: 23 August 2018
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Abstract
A broadband soil dielectric spectra retrieval approach ( 1 MHz– 2 GHz) has been implemented for a layered half space. The inversion kernel consists of a two-port transmission line forward model in the frequency domain and a constitutive material equation based on a [...] Read more.
A broadband soil dielectric spectra retrieval approach ( 1 MHz– 2 GHz) has been implemented for a layered half space. The inversion kernel consists of a two-port transmission line forward model in the frequency domain and a constitutive material equation based on a power law soil mixture rule (Complex Refractive Index Model - CRIM). The spatially-distributed retrieval of broadband dielectric spectra was achieved with a global optimization approach based on a Shuffled Complex Evolution (SCE) algorithm using the full set of the scattering parameters. For each layer, the broadband dielectric spectra were retrieved with the corresponding parameters thickness, porosity, water saturation and electrical conductivity of the aqueous pore solution. For the validation of the approach, a coaxial transmission line cell measured with a network analyzer was used. The possibilities and limitations of the inverse parameter estimation were numerically analyzed in four scenarios. Expected and retrieved layer thicknesses, soil properties and broadband dielectric spectra in each scenario were in reasonable agreement. Hence, the model is suitable for an estimation of in-homogeneous material parameter distributions. Moreover, the proposed frequency domain approach allows an automatic adaptation of layer number and thickness or regular grids in time and/or space. Full article
(This article belongs to the Special Issue Selected Papers from ISEMA 2018)
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