Performance of Electrical Spectroscopy using a Resper Probe to Measure the Salinity and Water Content of Concrete or Terrestrial Soil

This paper discusses the performance of electrical spectroscopy using a RESPER probe to measure the salinity s and volumetric content {\theta}W of the water in concrete or terrestrial soil. The RESPER probe is an induction device for spectroscopy which performs simultaneous and non invasive measurements of the electrical RESistivity 1/{\sigma} and relative dielectric PERmittivity {\epsilon}r of a subjacent medium. Numerical simulations establish that the RESPER can measure {\sigma} and {\epsilon} with inaccuracies below a predefined limit (10%) up to the high frequency band (HF). Conductivity is related to salinity and dielectric permittivity to volumetric water content using suitably refined theoretical models which are consistent with the predictions of Archie's and Topp's empirical laws. The better the agreement, the lower the hygroscopic water content and the higher s; so closer agreement is found with concrete containing almost no bonded water molecules provided these are characterized by a high {\sigma}. A novelty of the present paper is the application of a mathematical- physical model to the propagation of errors in the measurements, based on a sensitivity functions tool. The inaccuracy of salinity (water content) is the ratio (product) between the conductivity (permittivity) inaccuracy, specified by the probe, and the sensitivity function of salinity (water content) relative to conductivity (permittivity), derived from the constitutive equations of the medium. The main result is the model's prediction that the lower the inaccuracy for the measurements of s and {\theta}W (decreasing by as much as an order of magnitude from 10% to 1%), the higher {\sigma}; so the inaccuracy for soil is lower.Comment: 45 pages, 5 figures, 1 tabl

Design Of An Induction Probe For Simultaneous Measurements Of Permittivity And Resistivity

In this paper, we propose a discussion of the theoretical design and move towards the development and engineering of an induction probe for electrical spectroscopy which performs simultaneous and non invasive measurements on the electrical RESistivity \rho and dielectric PERmittivity \epsilon r of non-saturated terrestrial ground and concretes (RESPER probe). In order to design a RESPER which measures \rho and \epsilon r with inaccuracies below a prefixed limit (10%) in a band of low frequencies (LF) (B=100kHz), the probe should be connected to an appropriate analogical digital converter (ADC), which samples in uniform or in phase and quadrature (IQ) mode, otherwise to a lock-in amplifier. The paper develops only a suitable number of numerical simulations, using Mathcad, which provide the working frequencies, the electrode-electrode distance and the optimization of the height above ground minimizing the inaccuracies of the RESPER, in galvanic or capacitive contact with terrestrial soils or concretes, of low or high resistivity. As findings of simulations, we underline that the performances of a lock-in amplifier are preferable even when compared to an IQ sampling ADC with high resolution, under the same operating conditions. As consequences in the practical applications: if the probe is connected to a data acquisition system (DAS) as an uniform or an IQ sampler, then it could be commercialized for companies of building and road paving, being employable for analyzing "in situ" only concretes; otherwise, if the DAS is a lock-in amplifier, the marketing would be for companies of geophysical prospecting, involved to analyze "in situ" even terrestrial soils.Comment: 37 pages, 7 figures, 3 table

Amplitude and Phase inaccuracies due to the Round-Off noise of FFT processors

This report proposes to discuss the Fourier domain analysis performances of a RESPER probe. A uniform ADC, which is characterized by a sensible phase inaccuracy depending on frequency, is connected to a Fast Fourier Transform (FFT) processor, that is especially affected by a round-off amplitude noise linked to both the FFT register length and samples number. If the register length is equal to 32 bits, then the round-off noise is entirely negligible, else, once bits are reduced to 16, a technique of compensation must occur. In fact, oversampling can be employed within a short time window, reaching a compromise between the needs of limiting the phase inaccuracy due to ADC and not raising too much the number of averaged FFT values sufficient to bound the round-off. Finally, the appendix presents an outline of somewhat lengthy demonstrations needed to calculate the amplitude and especially phase inaccuracies due to the round-off noise of FFT processors

The calculation of ionospheric absorption with modern computers

New outcomes are proposed for ionospheric absorption starting from the Appleton-Hartree formula, in its complete form. The range of applicability is discussed for the approximate formulae, which are usually employed in the calculation of non-deviative absorption coefficient. These results were achieved by performing a more refined approximation that is valid under quasi-longitudinal (QL) propagation conditions. The more refined QL approximation and the usually employed non-deviative absorption are compared with that derived from a complete formulation. Their expressions, nothing complicated, can usefully be implemented in a software program running on modern computers. Moreover, the importance of considering Booker’s rule is highlighted. A radio link of ground range D = 1000 km was also simulated using ray tracing for a sample daytime ionosphere. Finally, some estimations of the integrated absorption for the radio link considered are provided for different frequencies

Integrated Geophysical Measurements on a Test Site for Detection of Buried Steel Drums

Geophysical methods are increasingly used to detect and locate illegal waste disposal and buried toxic steel drums. This study describes the results of a test carried out in clayey-sandy ground where 12 empty steel drums had previously been buried at 4-5 m below ground level. This test was carried out with three geophysical methods for steel-drum detection: a magnetometric survey, electrical resistivity tomography with different arrays, and a multifrequency frequency-domain electromagnetic induction survey. The data show that as partially expected, the magnetometric and electromagnetic induction surveys detected the actual steel drums buried in the subsurface, while the electrical resistivity tomography mainly detected the changes in some of the physical properties of the terrain connected with the digging operations, rather than the actual presence of the steel drums.Comment: 29 pages, 1 photo, 3 figure

Linking the Quasi-Normal and Natural Modes of an open cavity

The present paper proposes a comparison between the extinction theorem and the Sturm-Liouville theory approaches for calculating the e.m. field inside an optical cavity. We discuss for the first time to the best of our knowledge, in the framework of classical electrodynamics, a simple link between the Quasi Normal Modes (QNMs) and the Natural Modes (NMs) for one-dimensional (1D), two-sided, open cavities. The QNM eigenfrequencies and eigenfunctions are calculated for a linear Fabry-Perot (FP) cavity. The first-order Born approximation is applied to the same cavity in order to compare the first-order Born approximated and the actual QNM eigenfunctions of the cavity. We demonstrate that the first-order Born approximation for an FP cavity introduces symmetry breaking: in fact, each Born approximated QNM eigenfunction produces values below or above the actual QNM eigenfunction value on the terminal surfaces of the same cavity. Consequently, the two error-functions for an approximated QNM are not equal in proximity to the two terminal surfaces of the cavity.Comment: 38 pages, 3 figures; Earth-prints, http://hdl.handle.net/2122/5993 (2009

Ray theory formulation and ray tracing method. Application in ionospheric propagation

This work will lead to ray theory and ray tracing formulation. To deal with this problem the theory of classical geometrical optics is presented, and applications to ionospheric propagation will be described. This provides useful theoretical basis for scientists involved in research on radio propagation in inhomogeneous anisotropic media, especially in a magneto-plasma. Application in high frequencies (HF) radio propagation, radio communication, over-the-horizon-radar (OTHR) coordinate registration and related homing techniques for direction finding of HF wave, all rely on ray tracing computational algorithm. In this theory the formulation of the canonical, or Hamiltonian, equations related to the ray, which allow calculating the wave direction of propagation in a continuous, inhomogeneous and anisotropic medium with minor gradient, will be dealt. At least six Hamilton’s equations will be written both in Cartesian and spherical coordinates in the simplest way. These will be achieved by introducing the refractive surface index equations and the ray surface equations in an appropriate free-dimensional space. By the combination of these equations even the Fermat’s principle will be derived to give more generality to the formulation of ray theory. It will be shown that the canonical equations are dependent on a constant quantity H and the Cartesian coordinates and components of wave vector along the ray path. These quantities respectively indicated as ri(τ), pi(τ) are dependent on the parameter τ, that must increase monotonically along the path. Effectively, the procedure described above is the ray tracing formulation. In ray tracing computational techniques, the most convenient Hamiltonian describing the medium can be adopted, and the simplest way to choose properly H will be discussed. Finally, a system of equations, which can be numerically solved, is generated

Real Time 3D Ionospheric Modelling with Ray Tracing Application over Mediterranean Area

This poster deals with some practical examples of instantaneous 3D modelling of regional ionosphere, based on ionosondes data from the Istituto Nazionale di Geofisica e Vulcanologia, INGV. Characteristic anchor points have been chosen for each ionospheric region. These points are joint by an adaptive ionospheric profiler derived from the one used in Autoscala. For the F2 region the anchor point is given by the real height hmF2 of the layer and its critical frequency foF2. These values are obtained basing on the observed heights (hmF2ROME[OBS] and hmF2GIBILMANNA[OBS]) and critical frequencies (foF2ROME[OBS] and foF2GIBILMANNA[OBS]) of the F2 layer, which are compared with the corresponding monthly median given by CCIR maps using Shimazaki’s formulation. The differences dhmF2ROME = hmF2ROME[OBS] - hmF2ROME[CCIR] dhmF2GIBILMANNA = hmF2 GIBILMANNA [OBS] - hmF2 GIBILMANNA [CCIR] are thus computed and used in Kriging method to update the values given by CCIR maps. For the F1 region the critical frequency is derived form a solar zenith angle dependent model adjusted to match the values of foF1 measured in Rome and Gibilmanna. For the E region the height is set to 110 km, while the critical frequency is estimated by a standard solar zenith angle and solar activity dependent model. The model produces as an output a 3D matrix which can be profitably used as an input for a Matlab/Fortran based ray tracing program recently developed at INGV

Programma di ray-tracing nel magnetoplasma ionosferico

Il pacchetto applicativo “IONORT” per il calcolo del ray-tracing può essere utilizzato dagli utenti che impiegano il sistema operativo Windows. È un programma la cui interfaccia grafica con l’utente è realizzata in MATLAB. In realtà, il programma lancia un eseguibile che integra il sistema d’equazioni differenziali scritto in linguaggio Fortran e ne importa l’output nel programma MATLAB, il quale genera i grafici e altre informazioni sul raggio. A completamento di questa premessa va detto che questo pacchetto, nella sua parte computazionale, è figlio di un programma di Jones e Stephenson del 1975, dal titolo “A versatile three-dimensional ray-tracing computer program for radio waves in the ionosphere”, il quale a sua volta si rifaceva principalmente a un programma di ray-tracing di Dudziak (1961) e di altri ricercatori quali Croft and Gregory (1963), ecc.. Pertanto, come tutti i recenti programmi di ray- tracing, questo è un programma fatto di programmi e non si può non menzionare qui la prima applicazione numerica di ray-tracing di Haeselgrove (1955). Attualmente questi programmi sono stati ottimizzati e adattati alle applicazioni dei radar oltre l’orizzonte - Over The Horizon, OTH – [Coleman, 1998][Nickish, 2008] sfruttando le potenzialità di potenti computer e periferiche per la presentazione e l’utilizzo real-time nel problema delle coordinate registration CR. In ultimo, si precisa che tutti i parametri di input, output e le modalità d’uso del pacchetto applicativo sviluppato saranno forniti nel manuale utente allegato al CD