310 research outputs found
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
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
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 Bookerâs 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
Programma di ray-tracing nel magnetoplasma ionosferico
Il pacchetto applicativo âIONORTâ per il calcolo del ray-tracing puĂČ essere utilizzato dagli utenti che impiegano il sistema operativo Windows. Ă un programma la cui interfaccia grafica con lâutente Ăš realizzata in MATLAB. In realtĂ , il programma lancia un eseguibile che integra il sistema dâequazioni differenziali scritto in linguaggio Fortran e ne importa lâoutput 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, Ăš figlio di un programma di Jones e Stephenson del 1975, dal titolo âA versatile three-dimensional ray-tracing computer program for radio waves in the ionosphereâ, 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 Ăš un programma fatto di programmi e non si puĂČ 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 lâorizzonte - Over The Horizon, OTH â [Coleman, 1998][Nickish, 2008] sfruttando le potenzialitĂ di potenti computer e periferiche per la presentazione e lâutilizzo real-time nel problema delle coordinate registration CR.
In ultimo, si precisa che tutti i parametri di input, output e le modalitĂ dâuso del pacchetto applicativo sviluppato saranno forniti nel manuale utente allegato al CD
Magnetic anomalies of steel drums: a review of the literature and research results of the INGV
The detection and evaluation of the status of disposal sites that contain
hazardous waste materials is becoming an increasingly important element
in environmental investigations. Close cooperation between the Istituto
Nazionale di Geofisica e Vulcanologia (INGV; National Institute of Volcanology
and Geophysics) in Rome and the Italian environmental police
has resulted in numerous underground investigations of different buried
materials. Among the geophysical investigation tools, magnetometry is the
most effective, rapid and precise of all of the geophysical methods for localizing
buried steel drums. Analysis of magnetic map anomalies can provide
a variety of information about buried materials, including extension,
distribution and depth, with processing of the acquired magnetic data.
This information is also very useful in case of excavations that are aimed
at the recovery of hazardous waste. This study determines the most relevant
analyses reported in the literature, with modeling of magnetometric
methods for environmental applications both theoretically and experimentally.
Some studies and research results achieved by the INGV in relation
to magnetic anomalies produced by buried steel drums are also
reported, as found in field operations and as achieved from test sites
Inaccuracy Assessment for Simultaneous Measurements of Resistivity and Permittivity applying Sensitivity and Transfer Function Approaches
This paper proposes a theoretical modelling of the simultaneous and non
invasive measurement of electrical resistivity and dielectric permittivity,
using a quadrupole probe on a subjacent medium. A mathematical-physical model
is applied on propagation of errors in the measurement of resistivity and
permittivity based on the sensitivity functions tool. The findings are also
compared to the results of the classical method of analysis in the frequency
domain, which is useful for determining the behaviour of zero and pole
frequencies in the linear time invariant (LTI) circuit of the quadrupole. The
paper underlines that average values of electrical resistivity and dielectric
permittivity may be used to estimate the complex impedance over various
terrains and concretes, especially when they are characterized by low levels of
water saturation (content) and analyzed within a bandwidth ranging only from
low (LF) to middle (MF) frequencies. In order to meet the design specifications
which ensure satisfactory performances of the probe (inaccuracy no more than
10%), the forecasts provided by the sensitivity functions approach are less
stringent than those foreseen by the transfer functions method (in terms of
both a larger band of frequency f and a wider measurable range of resistivity
or permittivity).Comment: 50 pages, 11 figures, 3 tables; Earth-prints,
http://hdl.handle.net/2122/5180 (2009
The IONORT-ISP-WC system: inclusion of an electron collision frequency model for the D-layer
The IONORT-ISP system (IONOspheric Ray-Tracing â IRI-SIRMUP-PROFILES) was recently developed and tested by comparing the measured oblique ionograms over the radio link between Rome (41.89ÂșN, 12.48ÂșE), Italy, and Chania (35.51ÂșN, 24.02ÂșE), Greece, with the IONORT-ISP simulated oblique ionograms (Settimi et al., 2013). The present paper describes an upgrade of the system to include: a) electron-neutral collision have been included by using a collision frequency model that consists of a double exponential profile; b) the ISP three dimensional (3-D) model of electron density profile grid has been extended down to the altitude of the D-layer; c) the resolution in latitude and longitude of the ISP 3-D model of electron density profile grid has been increased from 2°x2° to 1°x1°. Based on these updates, a new software tool called IONORT-ISP-WC (WC means with collisions) was developed, and a database of 33 IONORT-ISP-WC synthesized oblique ionograms calculated for single (1-hop paths) and multiple (3-hop paths) ionospheric reflections. The IONORT-ISP-WC simulated oblique ionograms were compared with the IONORT-IRI-WC synthesized oblique ionograms, generated by applying IONORT in conjunction with the International Reference Ionosphere (IRI) 3-D electron density grid, and the observed oblique ionograms over the aforementioned radio link. The results obtained show that (1) during daytime, for the lower ionospheric layers, the traces of the synthesized ionograms are cut away at low frequencies because of HF absorption; (2) during night-time, for the higher ionospheric layers, the traces of the simulated ionograms at low frequencies are not cut off (very little HF absorption); (3) the IONORT-ISP-WC MUF values are more accurate than the IONORT-IRI-WC MUF values
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