La recherche de trace de vie, passée ou présente, sur Mars est l’objectif principal de la mission martienne européenne ExoMars (ESA-Roscosmos), dont le lancement est prévu pour l’été 2020. Cette mission déposera à la surface de Mars un Rover équipé d'instruments dédiés notamment à l’étude du sous-sol de la planète dont une foreuse collectera des échantillons. Le travail de thèse présenté dans ce manuscrit porte sur la préparation du retour scientifique de l’expérience du radar WISDOM (Water Ice and Subsurface Deposits Observation on Mars) embarqué à bord du Rover d’ExoMars 2020 et dont l’objectif principal est la caractérisation, avant forage, du sous-sol proche de Mars.Les données recueillies par WISDOM permettront d’identifier les formations géologiques du sous-sol et de comprendre les processus qui en sont à l’origine. Elles guideront également les opérations de prélèvement d'échantillons en profondeur. L'objectif de cette thèse était de préparer les outils de traitements et d'interprétation de ces données. Les résultats obtenus doivent permettre d'exploiter au mieux les possibilités de l'instrument et d’atteindre les ambitieux objectifs technologiques (en termes notamment de résolution et de sensibilité) et scientifiques fixés. Plus précisément, il s’agissait de mettre en place des outils pour aboutir à une description des premiers mètres du sous-sol via l’interprétation des radargrammes de WISDOM en termes d’épaisseur de couche(s), de rugosité des interfaces, de distribution en taille d’éventuelles roches enfouies, d’orientation des strates et de constantes géo-électriques pour les unités géologiques détectées.Ce travail de thèse a permis la mise en place d’une chaîne de traitement de données ainsi que d’outils d’interprétation (traitement automatique et modélisation du radar).L’approche a été d’aborder le problème à la fois du point de vue théorique et du point de vue pratique. En conséquence, ce travail s’est appuyé sur deux aspects indissociables que sont, d’une part, la modélisation (analytique et numérique) du fonctionnement de l’instrument dans son environnement et, d’autre part, le traitement des données simulées et/ou expérimentales obtenues en milieu contrôlé ou lors de campagnes de mesures organisées dans le cadre de cette thèse. / The main objective of European ExoMars (ESA-Roscosmos) mission is to search for signs of past or present life on Mars. The mission, to be launched in summer 2020, will deliver a rover on the surface of Mars. This rover accommodates instruments designed to investigate the close subsurface and, in particular, a drill that will collect samples at depth ranging from 0.5 m to 2 m. This thesis manuscript relates the preparation of the scientific return of the WISDOM (Water Ice and Subsurface Deposits Observation on Mars) radar experiment whose main objective is to characterize, before drilling, the shallow subsurface of Mars.Data obtained by WISDOM will shed the light on geological structures in the subsurface and therefore help trace back the history of the investigated Martian sites. Furthermore, they will help to identify the most promising locations to collect samples without jeopardizing the drill. The objective of this thesis was to efficiently pave the way to data interpretation and appraise WISDOM’s potentiality.In order to reach the ambitious scientific and technologic objectives (especially in terms of resolution and sensitivity) of WISDOM, we have developed tools that rely on a deep understanding of the instrument. The ultimate goal of these tools is to provide a reliable representation of the shallow subsurface and quantitative interpretation in terms of thickness and orientation of underground layers, roughness at interfaces, distribution of buried rocks and geoelectrical constant for each geological unit detected.This thesis manuscript describes the signal processing chain and tools developed in order to prepare WISDOM’s scientific return. When possible, approaches based on automatic detection were preferred. This work relies both on theoretical and practical investigations, including an accurate (analytical and numerical) modeling of the instrument operations and test on experimental data acquired during field campaigns on potential Martian analogs.

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The advancement of both electronics and instrumentation technology has fostered the development of multi-physics platforms that can probe the earth’s subsurface. Remote, non-destructive testing techniques have led to the increased deployment of electromagnetic waves in sensor technology. Electromagnetic wave techniques are reliable and have the capacity to sense materials and associated properties with minimal perturbation. However, meticulous data analyses and mathematical derivations reveal inconsistencies in some formulations. Thus, revisiting the fundamental physics that underlies both electrical impedance experimental setups and electromagnetic properties are paramount. This study aims to unravel inherent limitations in the understanding of the relationships between electromagnetic and non-electromagnetic properties that are relevant to the characterization of fluids in porous media. These correlations pervade porosity, permeability, specific surface, pore size distribution, tortuosity, fluid discrimination, diffusion coefficient, degree of saturation, viscosity, temperature, phase transformation, miscibility, salinity, and the presence of impurities. The focus is on the assessment of liquids, soils, rocks, and colloids using broad spectral frequency complex permittivity, conductivity, magnetic permeability, and nuclear magnetic resonance relaxometry. Broadband electrical properties measurement for saturated porous media can provide multiple physical phenomena: Ohmic conduction, electrode polarizations, Maxwell-Wagner spatial polarizations, rotational, and segmental polarizations. Liquids dominate the electromagnetic signatures in porous media as dry minerals are inherently non-polar and non-conductive. Results reveal that voltage drops due to the discontinuity of charge-carrier at the electrode-electrolyte interface named electrode polarization inherently affect the low-frequency electrical measurements both in two- and four-probe configurations. Rotational polarizations that occur in MHz-GHz ranges are defined by the electrical dipole moment and effective molecular volume. Both viscosity and effective molecular volume govern the NMR transverse relaxation time. An engineered soil suspension with ferromagnetic inclusions exhibits excellent characteristics for drilling fluid application. Overall, the study highlights the complementary nature of conductivity, permittivity, and NMR relaxation for the advanced characterization of fluid saturated geomaterials.

This work measured relative permittivity from 15.0 to 55.0 °C of aqueous solutions containing acetone or tetrahydrofuran using a BI 870 dielectric meter. A cubic polynomial fit resulted in coefficients for calculating permittivity as a function of temperature and mole fraction. Literature values for other co-solvent system resulted in similar polynomial coefficients. Using BI 870, permittivity measurements of ionic solutions were not possible because of high conductivity. A simple method using impedance spectroscopy measured these solutions. Impedance decreases with increasing temperature and decreases with increasing ionic strength. Due to the temperature dependence of impedance, all measurements were at 25.0 °C. Anions including bicarbonate, sulfate, acetate, and carbonate were determined using this method. Detection limits were at parts per trillion (ppt) levels. A simple sensor based on smaller stainless steel cylinders and a circuit to determine impedance is currently being developed in combination with an anion exchange column.

This study focus on trying to understand what factors regarding bumper materials and coatings affect the radar transparency at 77 GHz. Dielectric spectroscopy was done at 25 unique samples, consisting of various plastic substrates, primers, basecoats and clearcoats with the Free-spaced method in the 60-90 GHz region. The plastic substrate consisted of Polypropylene-blend with different fillers such as talc, carbon black and metal flakes. The basecoats analyzed were 2 solid factory coatings (one black and one white), 5 factory coating containing different effect pigments such as metal flakes, Xiralic, and Mica, 1 factory PVD coating and 2 aftermarket basecoats. All samples were provided by a Volvo Cars’ supplier, however, some samples were repainted with the aftermarket coatings. The complex permittivites were calculated for each PP-blend and coating from the curve fitting of the measured S-parameters from the Free-spaced method. Material analysis such as thickness measurements of the plastic substrate and coatings, ATR-FTIR spectroscopy, TGA and DSC were done at all plastic substrates. The plastic substrates and the coating were also observed in optical microscope and in SEM. The calculated permittivities were compared with the results from the material analysis and correlations between increased metal content in the basecoat and higher real permittivity were found. Some relationship between the size of the metal flakes and the radar transparency could also be observed. Further, correlations between higher real permittivity with higher concentration of talc and carbon black were detected. MATLAB was used to provide an example for optimization of the plastic thickness for a given basecoat in order to have minimal reflection at 77 GHz.

<p> A number of microwave measuring techniques for the measurement of the complex permittivity (^ɛ = ɛo ɛr - j σ/ω) have been investigated and a new method based on the replacement of the narrow wall of a rectangular wave-guide by a block of semi-conductor has been developed. This technique is shown to be suitable for the measurement of σ when σ >> ωɛo ɛr and for the measurement of σ and ɛr for σ ≃ ωɛo ɛr. </p> <p> An investigation has been made of the propagation characteristics of a rectangular wave-guide containing a centrally placed slab of semi-conductor parallel to the narrow walls of the guide. A comparison of exact solutions for the propagation constant in such a structure with the approximate solutions normally used has shown that the conditions for the validity of the approximate solutions are much more stringent than has been reported previously. It is further shown that under certain conditions the structure offers a convenient method of measuring the conductivity of a semi-conductor. In addition, a theoretical and experimental investigation of the effects of the higher order modes excited at the interface of such a structure with an empty wave-guide has been made. The study has shown that under certain conditions, the effects of these modes can be significant.</p> <p> A theoretical and experimental study has also been made of the effects of temperature, frequency and doping on the complex permittivity of lightly doped n-type germanium. Measurements of these effects which have not been reported previously have been made over a temperature range 100°K - 500°K at frequencies 9.25 and 34.5 GHz and confirm the theoretical model used.</p> / Thesis / Doctor of Philosophy (PhD)

According to the US Environmental Protection Agency (USEPA) sediment is a leading cause of water quality impairment (US EPA, 2002). The annual costs of sediment pollution in North America alone are estimated to range between $20 and $50 billion (Pimentel et al., 1995; Osterkamp et al, 1998, 2004). Due to the large spatial and temporal variations inherent in sediment transport, suspended sediment measurement is challenging. The overall goal of this research was to develop and test an inexpensive sensor for continuous suspended sediment monitoring in streams. This study was designed to determine if the gain and phase components of permittivity could be used to predict suspended sediment concentrations (SSC). A bench-scale suspension system was designed and tested to guarantee that there were no significant differences in the sediment suspension vertically or horizontally within the system. This study developed prediction models for SSC with input variables of temperature, specific conductivity, and gain and/or phase at multiple frequencies. The permittivity sensor is comprised of an electrode, power source, and a control box or frequency generator. Fixed and mixed effect, multiple, linear regression models were created and compared for target frequencies. However, it was not possible to meet the normality requirements for prediction accuracy. Partial Least Squares (PLS) regression techniques were also applied to gain and phase data for 127 of the 635 frequencies. The three models with the lowest error between predicted and actual values of SSC for validation were further tested with nine levels of independent validation data. The largest model error (error>50%) occurred for the top three models at 0 and 500 mg/L. At the higher concentrations error varied from 1-40%. Once the treatment levels, of the independent validation data set, were near 1000 mg/L the prediction accuracy increased for the top three models. Model 3A, a phase based model, preformed the best. Model 3A was able to predict six of the nine independent validation treatment levels within 300 mg/L. Future research will provide additional laboratory and field testing of the prototype sensor. / Ph. D.

Experiments at the University of Maryland Plasma Physics Laboratory have discovered an unusual temperature response in the form of a "thermal wave" which begins at the center and propagates towards the surface of a zinc oxide sample, when heated in a microwave cavity without the presence of oxygen. This effect is believed to be caused by the irregular temperature dependence of the dielectric properties of zinc oxide, particularly dielectric loss. Two thermocouple probes were used to measure the temperature response in a small cylindrical sample of zinc oxide packed in powder insulation, and heated in a microwave oven. In order to determine if the unusual response is caused by the dielectric properties, this work uses a finite-difference mathematical model to simulate the experiments, both for the case of zinc oxide heated in ordinary air, as well as for the case of zinc oxide heated in nitrogen. A revised version of the model is used to determine if the thermocouple probe has any effect on the temperature of the sample. The spatial and temporal temperature distribution results from the model indicate that the thermocouple probe has a negligible effect on the results and that the "thermal wave" can be attributed to the irregular temperature dependence of the dielectric loss of the material. / Master of Science

This project is focused on computer modeling of so-called meta-materials, and on the exploitation of metamaterials in the design of electrically small antennas. For modeling, COMSOL Multiphysics 3.3 was used. Simulations were focused on impedance matching of antennas. Antennas with metamaterials were compared with corresponding conventional antennas without metamaterial layers. The project does not investigate the creation of metamaterials; the project concentrates on their influence on crucial parameters of antennas. Next step this project is focused on optimalization this structure in program Matlab version R2009b. We used optimalization method PSO (swarms of particles) and results are comparing whit results calculating in COMSOL program.

Master of Science / Department of Biological & Agricultural Engineering / Naiqian Zhang / Four permittivity probes have been developed and tested to measure contaminants in water and in biodiesel fuel. An impedance meter was also used to measure the same contaminants. The pollutants measured in water were nitrate salts (potassium nitrate, calcium nitrate, and ammonium nitrate) and atrazine. The contaminants measured in biodiesel were water, glycerol, and glyceride. Each sensor measured the gain and phase of a sample with a known concentration of one of these pollutants. The resulting signals were analyzed using stepwise regression, partial least squares regression, artificial neural network, and wavelet transformation followed by stepwise regression to predict the concentration of the contaminant using changes in the gain and phase data measured by the sensor. The same methods were used to predict the molecular weight of the nitrate salts. The reliability of the probes and the regression methods were compared using the coefficient of determination and the root mean square error. The frequencies selected using stepwise regression were studied to determine if any frequencies were more useful than others in detecting the contaminants. The results showed that the probes were able to predict the concentration and the molecular weight of nitrates in water very accurately, with R2-values as high as 1.00 for the training data and 0.999 for the validation data for both concentration predictions and molecular weight predictions. The atrazine measurements were somewhat promising, the training R2-values were as high as 1.00 in some cases, but there were many low validation values, often below 0.400. The results for the biodiesel tests were also good; the highest training R2-value was 1.00 and the highest validation R2-value was 0.966.