106 research outputs found
Quantitative analysis of the 1981 and 2001 Etna flank eruptions: a contribution for future hazard evaluation and mitigation
Lava flows produced during Etna flank eruptions represent severe hazards
for the nearby inhabited areas, which can be protected by adopting prompt
mitigation actions, such as the building of diversion barriers. Lava
diversion measures were attempted recently during the 1983, 1991-93, 2001
and 2002 Etna eruptions, although with different degrees of success. In
addition to the complexity of barrier construction (due to the adverse
physical conditions), the time available to successfully slow the advance of
a lava flow depends on the lava effusion rate, which is not easily
measurable. One method to estimate the average lava effusion rate over a
specified period of time is based on a volumetric approach; i.e. the
measurement of the volume changes of the lava flow over that period. Here,
this has been compared to an approach based on thermal image processing,
as applied to estimate the average effusion rates of lava flows during the
1981 and 2001 Etna eruptions. The final volumes were measured by the
comparison of pre-eruption and post-eruption photogrammetric digital
elevation models and orthophotographs. Lava volume growth during these
eruptions was estimated by locating the flow-front positions from analyses
of scientific papers and newspapers reports, as well as from helicopter
photographs. The analyses of these two eruptions contribute to the
understanding of the different eruptive mechanisms, highlighting the role
of the peak effusion rate, which represents a critical parameter for planning
of mitigation actions and for hazard evaluation
APPLICATION OF LASER SCANNING SURVEYING TO ROCK SLOPES RISK ASSESSMENT ANALYSIS
The methods for understanding rock instability mechanisms and for evaluating potential destructive scenarios are of great importance in risk assessment analysis dedicated to the establishment of appropriate prevention and mitigation actions. When the portion of the unstable rock mass is very large, effective actions to counteract the risks are complex and expensive. In these conditions, an optimal risk management cannot ignore procedures able to faster and accurately acquire i) geometrical data for modeling the geometry of the rock walls and implementing reliable forecasting models and ii) monitoring data able to describe the magnitude and the direction of deformation processes. These data contributes to the prediction of the behavior of a landslide if the measurements are acquired frequently and reliable numerical models can be implemented. Innovative geomatic techniques, based on GPS, Terrestrial Laser Scanning Surveying (TLS), automated total station and satellite and ground SAR Interferometry, have been recently applied to define the geometry and monitoring the displacements of unstable slopes. Among these, TLS is mainly adopted to generate detailed 3D models useful to reconstruct rock wall geometry by contributing to the estimation of geo-mechanical parameters, that is orientation, persistence and apparent spacing of rock discontinuities. Two examples of applications of TLS technique to the analysis of a large front in a quarry and of a rock shoulder of a dam are presented
The Generalized Stochastic Microdosimetric Model: the main formulation
The present work introduces a rigorous stochastic model, named Generalized
Stochastic Microdosimetric Model (GSM2), to describe biological damage induced
by ionizing radiation. Starting from microdosimetric spectra of energy
deposition in tissue, we derive a master equation describing the time evolution
of the probability density function of lethal and potentially lethal DNA damage
induced by radiation in a cell nucleus. The resulting probability distribution
is not required to satisfy any a priori assumption. Furthermore, we generalized
the master equation to consider damage induced by a continuous dose delivery.
In addition, spatial features and damage movement inside the nucleus have been
taken into account. In doing so, we provide a general mathematical setting to
fully describe the spatiotemporal damage formation and evolution in a cell
nucleus. Finally, we provide numerical solutions of the master equation
exploiting Monte Carlo simulations to validate the accuracy of GSM2.
Development of GSM2 can lead to improved modeling of radiation damage to both
tumor and normal tissues, and thereby impact treatment regimens for better
tumor control and reduced normal tissue toxicities
On the robustness of the ammonia thermometer
Ammonia inversion lines are often used as probes of the physical conditions
in the dense ISM. The excitation temperature between the first two para
metastable (rotational) levels is an excellent probe of the gas kinetic
temperature. However, the calibration of this ammonia thermometer depends on
the accuracy of the collisional rates with H2. Here we present new collisional
rates for ortho-NH3 and para-NH3 colliding with para-H2 (J=0) and we
investigate the effects of these new rates on the excitation of ammonia.
Scattering calculations employ a new, high accuracy, potential energy surface
computed at the coupled-cluster CCSD(T) level with a basis set extrapolation
procedure. Rates are obtained for all transitions involving ammonia levels with
J <= 3 and for kinetic temperatures in the range 5-100 K. We find that the
calibration curve of the ammonia thermometer -- which relates the observed
excitation temperature between the first two para metastable levels to the gas
kinetic temperature -- does not change significantly when these new rates are
used. Thus, the calibration of ammonia thermometer appears to be robust.
Effects of the new rates on the excitation temperature of inversion and
rotation-inversion transitions are also found to be small.Comment: Accepted for publication in the MNRA
A tool for mapping the evolution of a lava field through the Etna video-surveillance camera network
In active volcanic areas it is often difficult carry out direct surveys during an eruption, remote sensing
techniques based on airborne/satellite platforms and ground-based sensors have remarkable monitoring
potentialities in terms of safety and observation capability. In addition, the recent development of high
resolution digital cameras, laser scanners and SAR instruments have improved the ability to obtain reliable
measurements for modelling the evolution of effusive and explosive eruptions by following the rate of
advancement of a lava flow or the dispersal of a volcanic plume. In order to collect data at an adequate level
of accuracy and frequency it is not possible to exclusively rely on airborne or satellite methods and it is
necessary to carry out measurements using also remote sensing instruments operating on the ground. Among
the other techniques, the use of a simplified photogrammetric approach based a video-surveillance camera
network represents a straightforward alternative for rapid mapping in active volcanic areas. Therefore a
procedure for optimizing and extending the observational capability of the Etna NEtwork of Thermal and
VIsible cameras (NETVIS) for systematically monitoring and quantifying surface sin-eruptive processes was
implemented. The activity included also the extension of the permanent video-surveillance network by
installing additional mobile stations. A dedicated tool for automatic processing of image datasets was
developed and tested in both simulated and real scenarios to obtain a time series of digital orthophotos for
tracking the evolution of a lava flow emplacement. The developed tool was tested by processing images
acquired by the Etna_NETVIS sensors, in particular from Monte Cagliato thermal camera, during the 2011
paroxysmal episodes of the New South East Crater that poured lava flows in the Valle del Bove.PublishedRoma, Italia5V. Sorveglianza vulcanica ed emergenzeope
The Use of Surveillance Cameras for the Rapid Mapping of Lava Flows: An Application to Mount Etna Volcano
In order to improve the observation capability in one of the most active volcanic areas in the world, Mt. Etna, we developed a processing method to use the surveillance cameras for a quasi real-time mapping of syn-eruptive processes. Following an evaluation of the current performance of the Etna permanent ground NEtwork of Thermal and Visible Sensors (Etna_NETVIS), its possible implementation and optimization was investigated to determine the locations of additional observation sites to be rapidly set up during emergencies. A tool was then devised to process time series of ground-acquired images and extract a coherent multi-temporal dataset of georeferenced map. The processed datasets can be used to extract 2D features such as evolution maps of active lava flows. The tool was validated on ad-hoc test fields and then adopted to map the evolution of two recent lava flows. The achievable accuracy (about three times the original pixel size) and the short processing time makes the tool suitable for rapidly assessing lava flow evolutions, especially in the case of recurrent eruptions, such as those of the 2011–2015 Etna activity. The tool can be used both in standard monitoring activities and during emergency phases (eventually improving the present network with additional mobile stations) when it is mandatory to carry out a quasi-real-time mapping to support civil protection actions. The developed tool could be integrated in the control room of the Osservatorio Etneo, thus enabling the Etna_NETVIS for mapping purposes and not only for video surveillance.Published1925V. Sorveglianza vulcanica ed emergenzeJCR Journalope
Terrestrial laser scanning survey in support of unstable slopes analysis. The case of Vulcano Island (Italy)
The capability to measure at distance dense cloud of 3D point has improved the relevance of geomatic techniques to support risk assessment analysis related to slope instability. This work focuses on quantitative analyses carried out to evaluate the effects of potential failures in the Vulcano Island (Italy). Terrestrial laser scanning was adopted to reconstruct the geometry of investigated slopes that is required for the implementation of numerical modeling adopted to simulate runout areas. Structural and morphological elements, which influenced past instabilities or may be linked to new events, were identified on surface models based on ground surveying. Terrestrial laser scanning was adopted to generate detailed 3D models of subvertical slopes allowing to characterize the distribution and orientation of the rock discontinuities that affect instability mechanism caused by critical geometry. Methods for obtaining and analyzing 3D topographic data and to implement simulation analyses contributing to hazard and risk assessment are discussed for two case studies (Forgia Vecchia slope and Lentia rock walls)
Assessing and improving the measuring capability of the Etna_NETVIS camera network for lava flow rapid mapping
This work is aimed at improving the performance of the ground NEtwork of Thermal and VIsible and cameras
located on Mt. Etna volcano (Etna_NETVIS) by optimizing its observational capability on lava flows evolution
and by developing dedicated tools for systematically measuring quantitative parameters of known accuracy.
The first goal will be achieved through the analysis of the geometrical configuration and its improvement
by means of the establishment of additional observation sites to be equipped with mobile stations, depending on
the area of interest. This will increment the spatial coverage and improve the observation of the most active areas
for surface sin-eruptive processes.
For the second objective we will implement new processing tools to permit a reliable quantitative use of
the data collected by the surveillance sensors of NETVIS, extending their capability in monitor the lava flow
thermal and spatial evolution and by providing georeferenced data for rapid mapping scope. The tool will be
used to automatically pre-process multitemporal datasets and will be tested on both simulated and real scenarios.
Thanks to data collected and archive by the NETVIS INGV team, we will have the opportunity to develop and test
the procedure in different operational conditions selected among the large number of lava flows coupled to lava
fountan events occurred between 2011 and 2013.
Additionally, Etna_NETVIS data can be used to downscale the information derived from satellite data and/or to
integrate the satellite datasets in case of incomplete coverage or missing acquisitions (both due to low revisiting
time or bad geometrical conditions). Therefore an additional goal is that of comparing/integrating quantitative data
derived from visible and radar satellite sensors with the maps obtained using Etna_NETVIS. The procedure will
take into account the discrepancy among the different datasets in terms of accuracy and resolution and will attempt
to provide a combined approach (based on error analysis and data weighting) to evaluate the final results reliability.
Preliminary results on the procedure and algorithm adopted for geometric and radiometric sensor calibration,
definition of optimized configurations through simulation and for extracting updated mapping data from
multi-temporal dataset will be presented.
This work is developed in the framework of the EU-FP7 project “MED-SUV” (MEDiterranean SUpersite
Volcanoes)
The foot (Fragmentation Of Target) experiment
Particle therapy uses proton or 12C beams for the treatment of deep-seated solid tumors. Due to the features of energy deposition of charged particles a small amount of dose is released to the healthy tissue in the beam entrance region, while the maximum of the dose is released to the tumor at the end of the beam range, in the Bragg peak region. However nuclear interactions between beam and patient tissues induce fragmentation both of projectile and target and must be carefully taken into account. In 12C treatments the main concern are long range fragments due to projectile fragmentation that release dose in the healthy tissue after the tumor, while in proton treatment the target fragmentation produces low energy, short range fragments along all the beam range. The FOOT experiment (FragmentatiOn Of Target) is designed to study these processes. Target nuclei (16O,12C) fragmentation induced by 150-250 AMeV proton beam will be studied via inverse kinematic approach. 16O,12C therapeutic beams, with the quoted kinetic energy, collide on graphite and hydrocarbons target to provide the cross section on Hydrogen. This configuration explores also the projectile fragmentation of these 16O,12C beams. The detector includes a magnetic spectrometer based on silicon pixel detectors and drift chamber, a scintillating crystal calorimeter with TOF capabilities, able to stop the heavier fragments produced, and a \u394E detector to achieve the needed energy resolution and particle identification. An alternative setup of the experiment will exploit the emulsion chamber capabilities. A specific emulsion chambers will be coupled with the interaction region of the FOOT setup to measure the production in target fragmentation of light charged fragments as protons, deuterons, tritons and Helium nuclei. The FOOT data taking is foreseen at the CNAO experimental room and will start during early 2018 with the emulsion setup, while the complete electronic detector will take data since 2019
Charge identification of fragments with the emulsion spectrometer of the FOOT experiment
The FOOT (FragmentatiOn Of Target) experiment is an international project designed to carry out the fragmentation cross-sectional measurements relevant for charged particle therapy (CPT), a technique based on the use of charged particle beams for the treatment of deep-seated tumors. The FOOT detector consists of an electronic setup for the identification of Z ≥ 3 fragments and an emulsion spectrometer for Z ≤ 3 fragments. The first data taking was performed in 2019 at the GSI facility (Darmstadt, Germany). In this study, the charge identification of fragments induced by exposing an emulsion detector, embedding a C2 H4 target, to an oxygen ion beam of 200 MeV/n is discussed. The charge identification is based on the controlled fading of nuclear emulsions in order to extend their dynamic range in the ionization response
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