427 research outputs found
SAR interferometry applications on active volcanoes: state of the art and perspectives for volcano monitoring
In this paper the application of the Synthetic Aperture Radar Interferometry (INSAR) on volcanology is analysed. Since it is not a real novelty among the different applications of INSAR in Earth Observation activities, at the beginning of this paper we analyse the state of the art of the researches in this field. During the discussion, the point of view of volcanologists is favoured because it is considered that the first applications were often badly aimed. Consequently, the initial INSAR performances in volcanology were overrated with respect to the real capabilities of this technique. This fact lead to discover some unexpected limitations in INSAR usage in volcano monitoring, but, at the same time, spurred on scientists to overcome these drawbacks. The results achieved recently allow to better apply SAR to volcanology; in the paper a possible operative work-plan aimed at introducing
INSAR in the volcano monitoring system is presented
A Measurement Tool for Investigating Cooling Lava Properties
This paper presents the development and uncertainty characterization of a system for the direct measurement of heat transfer in cooling lava. The system continuously measures the parameters involved in the cooling process and, particularly, in the formation of the crust. The aim is to allow the future development of a physical model of the cooling process itself. In order to realize a system that will be effective in such a hostile environment, the principles on which the instruments for radiation thermometry are based have been thoroughly investigated. A virtual instrument has been developed, interfacing the measuring system and the user, processing the incoming data, and producing an estimate of the uncertainty of the measurement chain. The various sources of uncertainty have been taken into account to produce an accurate estimate of the uncertainty associated with the measured data. The results of experimental tests are presented
Studio della correlazione tra il tremore vulcanico e l’attività esplosiva dell’Etna nel Gennaio - Febbraio 1999 mediante il sistema VoTA (Volcanic Tremor Analyzer)
Il seguente lavoro presenta lo studio della correlazione tra il tremore vulcanico e l'attività esplosiva dell'Etna nel gennaio-febbraio 1999 effettuato mediante l’implementazione e lo sviluppo del sistema automatico per l’analisi e la visualizzazione del tremore vulcanico VoTA (Volcanic Tremor Analizer).
In particolare, sono stati presi in considerazione cinque episodi eruttivi significativi dell’attività dell’Etna durante i quali il VoTA ha effettuato un’analisi on line del tremore vulcanico.
Successivamente, tali dati sono stati confrontati con le immagini dell’attività eruttiva riprese dalla telecamera di sorveglianza dell’Etna, permettendo di ricavare delle correlazioni tra le diverse fasi dell’attività esplosiva ed i corrispondenti valori del tremore vulcanico
Natural Polymers and Cosmeceuticals for a Healthy and Circular Life: The Examples of Chitin, Chitosan, and Lignin
The present review considers the design and introduction of new cosmeceuticals in the market, based on natural polymers and active molecules extracted from biomass, in a biomimetic strategy, starting with a consideration of the biochemical mechanisms, followed by natural precision biopolymer production. After introducing the contest of nanobiotechnology in relationship with its applicability for skin contact products and classifying the currently available sustainable polymers, some widely selected abundant biopolymers (chitin, chitosan, and lignin), showing specific functionalities (anti-microbial, anti-oxidant, anti-inflammatory, etc.), are described, especially considering the possibility to combine them in nanostructured tissues, powders, and coatings for producing new cosmeceuticals, but with potentialities in other sectors, such as biomedical, personal care, and packaging sectors. After observing the general increase in market wellness and beauty forecasts over the next few years, parallelisms between nano and macro scales have suggested that nanobiotechnology application expresses the necessity to follow a better way of producing, selecting, and consuming goods that will help to transform the actual linear economy in a circular economy, based on redesigning, reducing, recycling, and reusing
A quantitative approach for evaluating lava flow simulation reliability: the LavaSIM code applied to the 2001 Etna’s eruption
Many numerical codes have been developed to simulate the emplacement of lava flows for evaluating their possible evolutions and for defining, by a statistical approach, hazard maps useful for risk assessment and land planning. Although many examples of lava flow simulation can be found in literature, just a few of them attempted to quantify the correspondence between observed and simulated flows, nevertheless this is a crucial point especially if the codes are applied in real-time for risk managing.
The aim of this work was to define a methodology to quantitatively evaluate the reliability of simulation codes. In particular, it applied the LavaSIM code (Hidaka et al., 2005) to simulate the main lava flow emplaced on the South flank of Mt. Etna (Italy) between 18 July and 9 August 2001 which represents an ideal test case for validating numerical codes (Coltelli et al., 2007). It is a single flow both for its geometry and its temporal evolution and, many data are available to be used as input of the simulations (lava composition, pre- and post-eruption topographies, final flow volume and thickness and temporal evolution of average volumetric flow rates) and for checking their results (2D temporal evolution).
LavaSIM is the only full 3D model, thus able to account for the vertical variation of lava properties (temperature, viscosity, velocity and liquidus or solidus state). It is based on the 3D solution of the Navier-Stokes and the energy conservation equations and provides the most complete description of the lava cooling by considering radiation, conduction and convection. Its greatest peculiarity is to take into account crust formation by evaluating the enthalpy of every cell and by adopting an empiric threshold parameter (the solidification fraction of liquidity loss) to discriminate liquid and solid cells.
Different values of input parameters (viscosity, solidification fraction of liquidity loss, eruptive enthalpy and lava emissivity) have been adopted for evaluating their influence on the simulated lava distribution and cooling. A simulation with constant lava discharge, averaged on the whole eruption, was also run for checking how the feeding affects the lava spreading and cooling.
The results were first analyzed by comparing the planar expansions of real and simulated flows. A quantitative analysis was then carried out adopting two parameters for constraining both the lengthening and the planar expansion. For quantitatively verifying the correspondence between simulated and observed lengths, the Percent Length Ratio (PLR) was defined as the percentage ratio between simulated and observed lengths measured along the main flow direction. The second control parameter was the fitness function (e1) defined by Spataro et al. (2004) as the square root of the ratio between the intersection and the union of real and simulated areas. Since the e1 factor allows quantifying the simulated lateral spreading while PLR the flow lengthening, it is important to jointly analyze these two parameters.
This work showed that by combining the fitness function of Spataro et al. (2004) with the Percent Length Ratio, here defined, it is possible to constrain both the lateral spreading (by e1) and the flow lengthening (by the PLR). The analysis here presented also demonstrated the capability of the LavaSIM simulation code to account for the vertical variation of the lava properties and to simulate the crust formation
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
Radiosondaggi atmosferici nell’area etnea
RADIOSONDAGGI ATMOSFERICI NELL’AREA ETNE
A lab-scale experiment to measure terminal velocity of volcanic ash
In this paper, a novel methodology to measure trajectory and terminal velocity of volcanic ash in laboratory is presented. The methodology consists of: i) planning a lab-scale experiment in order to reproduce the sedimentation processes of fine volcanic ash based on the principle of dynamic similarity; ii) realizing the experimental set-up using a glass tank filled with glycerine, a web-cam based vision system and a dedicated image post processing tool able to estimate the position and
the terminal velocity of any particle falling in the tank; iii) performing a calibration procedure to accurately estimate the uncertainty on particle velocity; iv) comparing the experimental results with estimations obtained by some particle fallout models available in literature. Our results shows that there is a good agreement between experimental terminal velocities and those obtained applying a model which includes information on particle shape. The proposed methodology allows us to investigate how the particle shape affects the sedimentation processes. Since the latter is strategic to improve the accuracy on modeling ash fallout, this work will contribute to reduce risks to aviations during explosive eruptions
Application of differential SAR interferometry for studying eruptive event of 22July 1998 at Mt.Etna
One of the main objectives of the project
“Development and application of remote sensing
methods for the monitoring of active Italian
volcanoes” is directed to an operational use of
differential interferometry as a tool for volcano
monitoring. A first step to achieve this goal is to
test commercial software in order to evaluate
the most suitable for the project purposes. For
testing software, SAR images collected by
ERS2 from May 98 to August 98, before and
after the strong eruptive event occurred on 22
July 98 at Voragine crater of Etna, have been
selected. The explosive event was classified
sub-plinian producing a 12 km high eruptive
column and lapilli fell on land as far as 70 km
south-eastward along the dispersal axis. Pre,
post and across event image pairs have been
processed. In particular the pair 13 May 98-22
July 98, 22 July 98-26 August 98, 13 May 98-26
August 98 are used for testing respectively pre,
post and across event. In first analysis, the
fringes in the differential products show a positive
elevation trend in the summit area of the
volcano. In particular, an increased of about 1,5
fringes in the period pre-event, and a decrement
of 1 fringe in the period post-event is observed.
This result is agreement whit field of deformation
expected in such kind of event, confirming
that the interferometric processing tool used id
suitable for the purpose of the project
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