Восстановление профиля диэлектрической проницаемости плоскослоистой среды с учетом дисперсии при частотном зондировании

В данной работе рассмотрена задача восстановления профиля диэлектрической проницаемости плоскослоистой структуры с учетом дисперсии. При этом характер дисперсионной зависимости предполагается известным, а определению подлежит вид функции распределения реальной и мнимой частей диэлектрической проницаемости. В качестве информативного параметра использовалась частота. Предполагается, что исследуемая структура лежит на бесконечной подложке с известными электрофизическими свойствами. Рассмотрен итеративный метод решения обратной задачи рассеяния, сводящий ее к задаче минимизации сглаживающего функционала. В рамках этого метода была учтена дисперсия диэлектрической проницаемости, типичная для таких природных сред, как почвогрунты. Приведены схема вычислительного алгоритма и результаты численного моделирования

Signal Superposition Model with Mineralogy Based Spectroscopic Dielectric Modelin Wireless Underground Sensor Networks

The propagation of EM waves in soil is defined by permittivity and permeability which are in turn affected by the soil parameters such as soil moisture and texture. Therefore, a suitable Dielectric Model like MBSDM is required for the channel characterization of WUSN. Effect of soil parameters and environmental conditions on signal propagation is modelled using Superposition Model. The simulation of these stages is done in MATLAB for UG-UG, UG-AG and AG-UG scenarios. The system is further implemented on the ZYNQ ZC-702 hardware platform

Signal Superposition Model with Mineralogy Based Spectroscopic Dielectric Modelin Wireless Underground Sensor Networks

The propagation of EM waves in soil is defined by permittivity and permeability which are in turn affected by the soil parameters such as soil moisture and texture. Therefore, a suitable Dielectric Model like MBSDM is required for the channel characterization of WUSN. Effect of soil parameters and environmental conditions on signal propagation is modelled using Superposition Model. The simulation of these stages is done in MATLAB for UG-UG, UG-AG and AG-UG scenarios. The system is further implemented on the ZYNQ ZC-702 hardware platform

EFFECT OF SALINITY ON THE DIELECTRIC PROPERTIES OF GEOLOGICAL MATERIALS : IMPLICATION FOR SOIL MOISTURE DETECTION BY MEANS OF REMOTE SENSING

International audienceThis paper deals with the exploitation of dielectric properties of saline deposits for the detection and mapping of moisture in arid regions on both Earth and Mars. We then present a simulation and experimental study in order to assess the effect of salinity on the permittivity of geological materials and therefore on the radar backscattering coefficient in the [1-7GHz] frequency range. Dielectric mixing models were first calibrated by means of experimental measurements before being used as input parameters of analytical scattering models (IEM, SPM). Simulation results will finally be compared to field measurements (Pyla dune, Death Valley, Mojave Desert) and will be used for the interpretation of SAR data (AIRSAR, PALSAR)

Verification of the virtual bandwidth SAR (VB-SAR) scheme for centimetric resolution subsurface imaging from space

This work presents the first experimental demonstration of the virtual bandwidth synthetic aperture radar (VB-SAR) imaging scheme. VB-SAR is a newly-developed subsurface imaging technique which, in stark contrast to traditional close-proximity ground penetrating radar (GPR) schemes, promises imaging from remote standoff platforms such as aircraft and satellites. It specifically exploits the differential interferometric synthetic aperture radar (DInSAR) phase history of a radar wave within a drying soil volume to generate high- resolution vertical maps of the scattering through the soil volume. For this study, a stack of C-band VV polarisation DInSAR images of a sandy soil containing a buried target was collected in the laboratory whilst the soil moisture was varied - firstly during controlled water addition, and then during subsequent drying. The wetting image set established the moisture-phase relationship for the soil, which was then applied to the drying DInSAR image set using the VB-SAR scheme. This allowed retrieval of high resolution VB-SAR imagery with a vertical discrimination of 0.04m from a stack of 1m vertical resolution DInSAR images. This work unequivocally shows that the basic principles of the VB-SAR technique are valid and opens the door to further investigation of this promising technique

Quantitative analysis of guided wave in dielectric logging through numerical simulation

A good knowledge of the electromagnetic (EM) wave propagation behaviors in dielectric logging (DL) and borehole radar (BHR) surveying is critically important for the optimization of tool design and implementation, and interpretation of the acquired logging data, as well as understanding the influences of the dielectric permittivity and conductivity of the formation on the EM waves. This letter reported a novel method for the numerical simulation and analysis of the guided wave (GW) propagating along a metallic pipe in a typical DL configuration. A numerical simulation with the 3-D finite-difference time-domain (FDTD) method was applied to the broadband DL tool to obtain the wavefield and responses of the receiver. By monitoring the wave attenuation along the metallic drill collar, the intensity of the GW and loss factor can be determined. The coupling efficiency of the GW can be obtained when the total power emitted from the transmitting antenna is known. Simulation results revealed that the coupling efficiency of the GW changes with the water saturation of the formation and frequency. The simulation also suggest, by installing a slope structure adjacent to the transmitting antenna, the energy coupled into the GW could be reduced at different levels. Finally, the relationship between the received signals' amplitude and GW's coupling efficiency showed the quantified contribution of the GW to the received sign

Microwave material characterization of alkali-silica reaction (ASR) gel in cementitious materials

Since alkali-silica reaction (ASR) was recognized as a durability challenge in cement-based materials over 70 years ago, numerous methods have been utilized to prevent, detect, and mitigate this issue. However, quantifying the amount of produced ASR byproducts (i.e., ASR gel) in-service is still of great interest in the infrastructure industry. The overarching objective of this dissertation is to bring a new understanding to the fundamentals of ASR formation from a microwave dielectric property characterization point-of-view, and more importantly, to investigate the potential for devising a microwave nondestructive testing approach for ASR gel detection and evaluation. To this end, a comprehensive dielectric mixing model was developed with the potential for predicting the effective dielectric constant of mortar samples with and without the presence of ASR gel. To provide pertinent inputs to the model, critical factors on the influence of ASR gel formation on dielectric and reflection properties of several mortar samples were investigated at R, S, and X-band. Effects of humidity, alkali content, and long-term curing conditions on ASR-prone mortars were also investigated. Additionally, dielectric properties of chemically different synthetic ASR gel were also determined. All of these, collectively, served as critical inputs to the mixing model. The resulting developed dielectric mixing model has the potential to be further utilized to quantify the amount of produced ASR gel in cement-based materials. This methodology, once becomes more mature, will bring new insight to the ASR reaction, allowing for advancements in design, detection and mitigation of ASR, and eventually has the potential to become a method-of-choice for in-situ infrastructure health-monitoring of existing structures --Abstract, page v