Search results for " resistivity"

Growth and characterisation of MnTe crystals

2001

We report on the low temperature growth of MnTe crystals by means of travelling solution methods. Two different processes are considered; a classical THM process using a low temperature presynthesised MnTe ingot, and a modified THM process, in which an increasing length of solvent zone collects the tellurium that was added to the stoichiometric charge to decrease the reaction temperature. Ingots from the two methods are analysed by means of scanning electron microscopy, X-ray diffractometry, resistivity, susceptibility and optical absorption measurements.

Hydrogeological and geotechnical modeling of the foundation soils of Maredolce Lake in Palermo, aided by geophysical surveys

2019

The cultural heritage of Maredolce (Palermo) includes an Arab-Norman castle that originally stood on the shores of an artificial lake carved out of a basin dug out of the calcarenite and filled with water thanks to the channeling of the springs of San Ciro upstream. Subsequently, the lowering of the water table and the high hydraulic permeability of the outcropping rocks caused the lake to dry up. Recently, a project of enhancement of the cultural heritage required the restoration of the lake. The geophysical study presented here, including the integrated use of different techniques such as electrical and seismic tomography, Multichannel Analysis of the Surface Waves and ambient vibration r…

USING A.R.P. PROXIMAL SURVEY TO MAP CALCIC HORIZON DEPTH IN VINEYARDS

2012

The investigation of spatial variability of soil water retention capacity and depth is essential for a correct and economical planning of water supply of a vineyard. The advantage of measuring soil electrical properties by proximal sensors is the ability to operate with mobile and non-destructive tools, quicker than the traditional soil survey. A.R.P. (Automatic Resistivity Profiling) is a mobile soil electrical resistivity (ER) mapping system conceived by Geocarta (Paris, France), and it is comprised by a couple of transmitter sprocket-wheels, which inject current within the soil, and three couples of receiver sprocket-wheels, which measure the voltage-drop at three different depths, about…

Multivariate modelling of geophysical tomography data to identify a tectonized area

2018

An integrated analysis approach, based on geological investigations and 2D high-resolution shallow geophysical data, was proposed along a slope in the Bellolampo landfill area (Palermo, Italy) where the presence of a fault zone was hypothesized. Geophysical surveys included electrical resistivity tomography (ERT), induced polarization tomography (IPT) and seismic refraction tomography (SRT) techniques. The inversion of single geophysical parameter often does not allow to justify the complexity of the subsoil structures. The most appropriate solution should be to add additional physical or geological information so to get a constrained geological model. However, it is not at all easy to work…

Integrated archaeological and geophysical survey for searching the roman temple of Augustus in Terragona, Spain

2009

The summit part of Mount Etna revealed by High Resolution DC Electrical Resistivity Tomography coupled with complementary geophysical and soil gas te…

2016

Between 25 June and 13 July 2015 a very deep ERT profile (Pole-Dipole configuration, 40m spacingbetween electrodes and a remote electrode located at ~10km from the acquisition points) has been performedin the framework of the “MED-SUV” Project. Self-potential, soil gas concentrations (CO2, 222Rn, 220Rn, He,H2 and CH4) and soil temperature measurements were coupled to the ERT profile with a spacing of 20m(except for Rn: 40m). The NE-SW profile crossed Etnas summit craters in the middle of the 5720m ERTtotal length. Six roll along protocols of . of the dispositive (600m out of 2520m tot) have been carried outand, for the first time, a high resolution DC ERT profile reached the noticeable inve…

A constrained geophysical model of the landslide that affects the Agrigento Cathedral

2012

The MYG methodology to carry out 3D electrical resistivity tomography on media covered by vulnerable surfaces of artistic value

2010

Electrical Resistivity Tomography (ERT) is not yet frequently used in the study of walls, floors and foundations of buildings of artistic value, like Ground Penetrating Radar (GPR) or other commoner techniques, although it exhibits a great potentiality in terms of resolution power. The main limitation for the applicability of ERT to the Cultural Heritage field arises from the method of current injection: it is often necessary to drive current electrodes into small perforations on the acquisition surface in order to get a current flow sufficient to obtain a good signal-to-noise ratio. To overcome this limitation the Maximum-Yield Grid (MYG) methodology has been developed, in which only a small fr…

Statistical approach for cavity detection using seismic refraction and electrical resistivity data

2017

To test limitations and effectiveness of seismic tomography when coupled to geoelectrical technique for cavity detection 2D synthetic models were used. Synthetic models were created with different number of cavity and blocks of highly cohesive lithological material (high seismic velocity and resistivity values). A modified version of multiple gradient (Martorana et al., 2016) has been used for electrical sequence. The cluster analysis performed on static units defined by electrical resistivity values, P wave velocities, and seismic density on coincident sections, allowed to interpret subsoil structures. The use of the non-hierarchical clustering algorithm has been chosen because it is less …

A geophysical and geochemical approach for seawater intrusion assessment in the Acquedolci coastal aquifer (Northern Sicily)

2007

Vertical electrical sounding (VES’) surveys and chemical analyses of groundwater have been executed in the coastal plain of Acquedolci (Northern Sicily), with the aim to circumscribe seawater intrusion phenomena. This urbanized area is representative of a more general problem interesting most of Mediterranean littoral areas, where intensive overdraft favors a heavy seawater intrusion through the coastline. Aquifer resistivity seems decisively to be conditioned by the chlorine and magnesium content in the main aquifer of the region. Schlumberger VES’, together with piezometric and chemical–physical information of groundwater, allowed us to perform hydrogeological and geophysical elaborations…