189,096 research outputs found
Three-dimensional electrical and seismic tomography for assessing the state of conservation of a masonry wall
No full textGeophysical non-destructive testing has been applied worldwide during last decades for understanding the inner
geometry, the constructive materials and the degree of conservation of ancient buildings affected by the ravages of time,
human interventions or natural phenomena (e.g. Polymenakos et al. 2005; Tsokas et al., 2013).
The integrated approach presented in this work encompasses the use of Electrical Resistivity Tomography (ERT) and
seismic tomography aiming to assess the current state of conservation of a Roman masonry building, named "Casa di
Diana", located at the Ostia Antica archaeological site (Rome, Italy).
Three-dimensional ERT and seismic tomography investigations were focused on an inner wall, made in opus
caementicium, prone to both rising damp and cracking phenomena, in order to reconstruct a 3D model where anomalous
zones would be highlighted. ERT dataset were inverted with the VEMI interface (De Donno & Cardarelli, 2015), while
seismic tomography inversion was performed by means of the algorithm after Cardarelli & Cerreto (2002).
Results show that low resistivity and P-wave velocity values can be associated to the presence of the inner mortar,
while higher values of both parameters were observed for the existence of the outer brick component. Overall, with
reference to a previous work where a small-scale sample of a Roman masonry wall was analysed in the laboratory using
seismic tomography (Cardarelli & de Nardis, 1999), the brick part seems to be in good conditions (optimal VP=1400 m/s,
recovered VP=1300 m/s), while the low velocity values of the mortar (optimal VP=500 m/s, recovered VP=250 m/s) can
potentially represent an anomaly due to degradation phenomena. Therefore this approach can be employed to reconstruct
a 3D model of an archaeological wall in order to plan the recovery actions
Arbuscular mycorrhizal inoculation is a useful to improve crop tolerance to salinity and adverse soil pH conditions
No full text2D inversion of borehole logging data for simultaneous determination of rock interfaces and petrophysical parameters
No full textIn the paper a 2D joint inversion method is presented, which is applicable for the simultaneous determination of layer thickness variation and petrophysical parameters by processing well-logging data acquired in several boreholes along the profile. The so-called interval inversion method is tested on noisy synthetic data sets generated on hydrocarbon-bearing reservoir models. Numerical experiments are performed to study the convergence and stability of the inversion procedure. Data and model misfit, function distance related to layer thickness fitting are measured as well as estimation errors and correlation coefficients are computed to check the accuracy and reliability of inversion results. It is shown that the actual inversion procedure is stable and highly accurate, which arises from the great over-determination feature of the inverse problem. Even a case study is attached to the paper in which interval inversion procedure is applied for processing of multi-borehole logging data acquired in Hungarian hydrocarbon exploratory wells in order to determine petrophysical parameters and lateral changes of layer thicknesses
The Resistive Cylindrical Chamber
No full textA new generation of gaseous particle detectors named Resistive Cylindrical Chamber (RCC) (Cardarelli, 2021; Rocchi, 2022) [1,2] has been developed to overcome the limitations of Resistive Plate Chambers (Santonico and Cardarelli, 1981) [3] and broaden their application range. The principle behind this new technology consists in the transition from a planar to a cylindrical geometry while maintaining an almost planar electric field. The cylindrical structure of the electrodes allows to reach the following goals: increase the gas pressure to improve the intrinsic efficiency of the detector even for thin gas gaps or light gas mixtures; design the detector in order to produce an electric field gradient possibly useful to contain the development of the avalanche discharge. These features could lead to design detectors of simple mechanical realization with time resolution comparable with that of MRPCs maintaining a high efficiency of detection on a single thin gas-gap. The device pressurization could also allows to use new gases in view of the transition to eco-friendly gas
Comparison between GPR measurements and ultrasonic tomography with different inversion algorithms: an application to the base of an ancient Egyptian sculpture
No full textBy late 2008 one of the most important pieces of the ‘Museo delle Antichit`a Egizie’ of Turin,
the sculpture of the Pharaoh with god Amun, was planned to be one of the masterpieces of a
travelling exhibition in Japan. The ‘Fondazione Museo delle Antichit`a Egizie di Torino’, who
manages the museum, was concerned with the integrity of the base of the statue which actually
presents visible signs of restoration dating back to the early 19th century. It was required to
estimate the persistence of the visible fractures, to search for unknown ones and to provide
information about the overall mechanical strength of the base. To tackle the first question a
GPR reflection survey along three sides of the base was performed and the results were
assembled in a 3D rendering. As far as the second question is concerned, two parallel,
horizontal ultrasonic 2D tomograms across the base were made. We acquired, for each
section, 723 ultrasonic signals corresponding to different transmitter and receiver positions.
The tomographic data were inverted using four different software packages based upon
different algorithms. The obtained velocity images were then compared each other, with the
GPR results and with the visible fractures in the base. A critical analysis of the comparisons is
finally presented
Evaluation of restoration results on the Antonino and Faustina Temple in Rome through seismic transmission tomography: Comparison of P-wave velocities before and after restoration
No full textTo evaluate the state of preservation of two columns of the Pronao of the Antonino and Faustina temple in the Roman forum (Rome, Italy - 141 A.D.), 2D seismic tomography was used. In this paper we describe the results of seismic transmission tomography before and after restoration, comparing sections of the two restored columns. The aim of this work was to test the validity of seismic tomography to guide the restorer during the restoration. We assessed the value of using this method to determine elastic properties in terms of P-wave velocity and, consequently, identify zones with little cracks and fractures, and detect improved dynamic characteristics after the restoration. Considering the dimensions nad shape of the studied objects, particular field and acquisition techniques were adopted. To obtain high-resolution tomograms, we used piezoelectric sensors with high cut-off frequency and short sampling intervals for the recorder unit; furthermore a particular recording technique was used to avoid reading errors (double trigger). The investigated sections are divided into cells, whose dimensions are calculated using Fresnel theory and a priori information. To invert the data we used the Least Square Inversion (LSI) method modified with variable damping factors, taking into account the mean slowness of the marble as constraint. The results of comparing P-wave velocities indicate that transmission tomography is able to detect differences in the elastic properties that occur before and after restoration. These results provide information to evaluate the degree of restoration needed, and to guide and help to improve the work of the restorer
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