DSpace Collection:
http://hdl.handle.net/2122/289
2014-07-23T08:16:33ZThe COMPLEIK subroutine of the IONORT-ISP system for calculating the non-deviative absorption: A comparison with the ICEPAC formula
http://hdl.handle.net/2122/8864
Title: The COMPLEIK subroutine of the IONORT-ISP system for calculating the non-deviative absorption: A comparison with the ICEPAC formula
Authors: Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: The present paper proposes to discuss the ionospheric absorption, assuming a quasi-flat layered ionospheric medium, with small horizontal gradients. A recent complex eikonal model [Settimi et al., 2013b] is applied, useful to calculate the absorption due to the ionospheric D-layer, which can be approximately characterized by a linearized analytical profile of complex refractive index, covering a short range of heights between h1= 50 km and h2= 90 km. Moreover, Settimi et al. [2013c] have already compared the complex eikonal model for the D-layer with the analytical Chapman’s profile of ionospheric electron density; the corresponding absorption coefficient is more accurate than Rawer’s theory [1976] in the range of middle critical frequencies. Finally, in this paper, the simple complex eikonal equations, in quasi-longitudinal (QL) approximation, for calculating the non-deviative absorption coefficient due to the propagation across the D-layer are encoded into a so called COMPLEIK (COMPLex EIKonal) subroutine of the IONORT (IONOspheric Ray-Tracing) program [Azzarone et al., 2012]. The IONORT program, which simulates the three-dimensional (3-D) ray-tracing for high frequencies (HF) waves in the ionosphere, runs on the assimilative ISP (IRI-SIRMUP-P) discrete model over the Mediterranean area [Pezzopane et al., 2011]. As main outcome of the paper, the simple COMPLEIK algorithm is compared to the more elaborate semi-empirical ICEPAC formula [Stewart, undated], which refers to various phenomenological parameters such as the critical frequency of E-layer. COMPLEIK is reliable just like the ICEPAC, with the advantage of being implemented more directly. Indeed, the complex eikonal model depends just on some parameters of the electron density profile, which are numerically calculable, such as the maximum height.2014-01-14T23:00:00ZMonitoraggio sismico del territorio nazionale: stato dell'arte e sviluppo delle reti di monitoraggio sismico
http://hdl.handle.net/2122/8813
Title: Monitoraggio sismico del territorio nazionale: stato dell'arte e sviluppo delle reti di monitoraggio sismico
Authors: Sergio, Guardato; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia
Abstract: Il sistema CUMAS (Cabled Underwater Module
for Acquisition of Seismological data) è un
prodotto tecnologico-scientifico complesso nato
con il Progetto V4 [Iannaccone et al., 2008] allo
scopo di monitorare l’area vulcanica dei Campi
Flegrei (fenomeno del bradisismo).
Si tratta di un modulo sottomarino cablato e
connesso a una boa galleggiante (meda elastica). Il
sistema è in grado di acquisire e trasmettere alla
sala di monitoraggio dell’OV, in continuo e in
tempo reale, sia i segnali sismologici sia quelli di
interesse geofisico ed oceanografico (maree,
correnti marine, segnali acustici subacquei,
parametri funzionali di varia natura).
Il sistema è in grado di ricevere comandi da remoto
per variare diversi parametri di acquisizione e di
monitorare un cospicuo numero di variabili di
funzionamento.
Il sistema si avvale del supporto di una boa
galleggiante attrezzata. La boa è installata a largo
del golfo di Pozzuoli (Napoli) a circa 3 km dalla
costa. Il modulo sottomarino, collegato via cavo
alla parte fuori acqua della boa, è installato sul
fondale marino a una profondità di circa 100 metri.2010-12-31T23:00:00ZScientific review on the Complex Eikonal, and research perspectives for the Ionospheric Ray-tracing and Absorption
http://hdl.handle.net/2122/8712
Title: Scientific review on the Complex Eikonal, and research perspectives for the Ionospheric Ray-tracing and Absorption
Authors: Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: The present paper conducts a scientific review on the complex eikonal, extrapolating the research perspectives on the
ionospheric ray-tracing and absorption. As regards the scientific review, the eikonal equation is expressed, and some
complex-valued solutions are defined corresponding to complex rays and caustics. Moreover, the geometrical optics
is compared to the beam tracing method, introducing the limit of the quasi-isotropic and paraxial complex optics
approximations. Finally, the quasi-optical beam tracing is defined as the complex eikonal method applied to ray-tracing,
discussing the beam propagation in a cold magnetized plasma. As regards the research perspectives, this paper proposes to
address the following scientific problem: in absence of electromagnetic (e.m.) sources, consider a material medium which is
time invariant, linear, optically isotropic, generally dispersive in frequency and inhomogeneous in space, with the additional
condition that the refractive index is assumed varying even strongly in space. The paper continues the topics discussed by
Bianchi et al. [2009], proposing a novelty with respect to the other referenced bibliography: indeed, the Joule’s effect is assumed
non negligible, so the medium is dissipative, and its electrical conductivity is not identically zero. In mathematical terms, the
refractive index belongs to the field of complex numbers. The dissipation plays a significant role, and even the eikonal function
belongs to the complex numbers field. Under these conditions, for the first time to the best of our knowledge, suitable
generalized complex eikonal and transport equations are derived, never discussed in literature. Moreover, in order to solve the
ionospheric ray-tracing and absorption problems, we hint a perspective viewpoint. The complex eikonal equations are derived
assuming the medium as optically isotropic. However, in agreement with the quasi isotropic approximation of geometrical optics,
these equations can be referred to the Appleton-Hartree’s refractive index for an ionospheric magneto-plasma, which becomes
only weakly anisotropic in the presence of Earth’s magnetic induction field. Finally, a simple formula is deduced for a simplified
problem. Consider a flat layering ionospheric medium, so without any horizontal gradient. The paper proposes a new formula,
useful to calculate the amplitude absorption due to the ionospheric D-layer, which can be approximately modelled by a linearized
complex refractive index, because covering a short range of heights, between h1= 50 km and h2= 80 km about.2013-03-19T23:00:00ZRepeat-station surveys: implications from chaos and ergodicity of the recent geomagnetic field
http://hdl.handle.net/2122/8683
Title: Repeat-station surveys: implications from chaos and ergodicity of the recent geomagnetic field
Authors: De Santis, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Qamili, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cianchini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: The present geomagnetic field is chaotic and ergodic: chaotic because it can no longer be predicted beyond around 6 years; and ergodic in the sense that time averages correspond to phase-space averages. These properties have already been deduced from complex analyses of observatory time series in
a reconstructed phase space [Barraclough and De Santis 1997] and from global predicted and definitive models of differences in the time domain [De Santis et al. 2011]. These results imply that there is a strong necessity to make repeat-station magnetic surveys more frequently than every 5 years. This, in turn, will also improve the geomagnetic field secular variation models. This report provides practical examples and case studies.2013-04-17T22:00:00ZHigh resolution finite volume central schemes for a compressibile two-phase model
http://hdl.handle.net/2122/8273
Title: High resolution finite volume central schemes for a compressibile two-phase model
Authors: La Spina, G.; Dipartimento di Matematica L.Tonelli, University of Pisa, Italy; De' Michieli Vitturi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia
Abstract: A modi_cation of the Kurganov, Noelle, Petrova central-upwind scheme [A. Kurganov et al., SIAM J. Sci. Comput., 23 (2001), pp. 707{740] for hyperbolic systems of conservation laws is presented. In this work, the numerical scheme is applied to a single-temperature model for compressible two-phase ow with pressure and velocity relaxations [E. Romenski et al., J. Sci. Comput., 42 (2010), pp. 68{95]. The system of governing equations of this model are expressed in conservative form, which is the necessary condition to use a central scheme. The numerical scheme presented is not based on the complete characteristic decomposition, but only on the information about the local speeds of propagation given by the maximum and minimum eigenvalue of the Jacobian of the uxes. We propose to use the numerical ux formulation of the central-upwind scheme in conjunction with a second-order reconstruction of the primitive variables and the MUSCL-Hancock method, where the boundary extrapolated values are evolved by half time step before the computation of the numerical uxes. To investigate the accuracy and robustness of the proposed scheme, two 1D Riemann-problems of an air/water mixture and a 2D shock-bubble-interaction problem are presented. Furthermore, a detailed comparison with the second order GFORCE scheme and the _rst order Lax-Friedrichs scheme is shown. To integrate the source terms an operator splitting approach is used and, under suitable conditions, it is shown that this integration can be computed analytically.2011-12-31T23:00:00ZIf Space is Material, What Inertia Should Be?
http://hdl.handle.net/2122/7747
Title: If Space is Material, What Inertia Should Be?
Authors: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia
Editors: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Cwojdzinski, Stefan; Polish Geological Survey
Abstract: (extended abstract)2011-10-03T22:00:00ZPorting and optimizing MAGFLOW on CUDA
http://hdl.handle.net/2122/7603
Title: Porting and optimizing MAGFLOW on CUDA
Authors: Bilotta, G.; Università di Catania, Dipartimento di Matematica e Informatica, Catania, Italy; Rustico, E.; Università di Catania, Dipartimento di Matematica e Informatica, Catania, Italy; Herault, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Vicari, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Russo, G.; Università di Catania, Dipartimento di Matematica e Informatica, Catania, Italy; Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Gallo, G.; Università di Catania, Dipartimento di Matematica e Informatica, Catania, Italy
Abstract: The MAGFLOW lava simulation model is a cellular automaton developed
by the Sezione di Catania of the Istituto Nazionale di Geofisica e
Vulcanologia (INGV) and it represents the peak of the evolution of cellbased
models for lava-flow simulation. The accuracy and adherence to
reality achieved by the physics-based cell evolution of MAGFLOW comes
at the cost of significant computational times for long-running simulations.
The present study describes the efforts and results obtained by porting the
original serial code to the parallel computational platforms offered by
modern video cards, and in particular to the NVIDIA Compute Unified
Device Architecture (CUDA). A number of optimization strategies that
have been used to achieve optimal performance on a graphic processing
units (GPU) are also discussed. The actual benefits of running on the GPU
rather than the central processing unit depends on the extent and duration
of the simulated event; for large, long-running simulations, the GPU can
be 70-to-80-times faster, while for short-lived eruptions with a small extents
the speed improvements obtained are 40-to-50 times.2010-12-31T23:00:00ZMoving least-squares corrections for smoothed particle hydrodynamics
http://hdl.handle.net/2122/7602
Title: Moving least-squares corrections for smoothed particle hydrodynamics
Authors: Bilotta, G.; Università di Catania, Dipartimento di Matematica e Informatica, Catania, Italy; Russo, G.; Università di Catania, Dipartimento di Matematica e Informatica, Catania, Italy; Herault, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia
Abstract: First-order moving least-squares are typically used in conjunction with
smoothed particle hydrodynamics in the form of post-processing filters for
density fields, to smooth out noise that develops in most applications of
smoothed particle hydrodynamics. We show how an approach based on
higher-order moving least-squares can be used to correct some of the main
limitations in gradient and second-order derivative computation in classic
smoothed particle hydrodynamics formulations. With a small increase in
computational cost, we manage to achieve smooth density distributions
without the need for post-processing and with higher accuracy in the
computation of the viscous term of the Navier–Stokes equations, thereby
reducing the formation of spurious shockwaves or other streaming effects
in the evolution of fluid flow. Numerical tests on a classic two-dimensional
dam-break problem confirm the improvement of the new approach.2010-12-31T23:00:00ZAn emergent strategy for volcano hazard assessment: From thermal satellite monitoring to lava flow modeling
http://hdl.handle.net/2122/7600
Title: An emergent strategy for volcano hazard assessment: From thermal satellite monitoring to lava flow modeling
Authors: Ganci, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Vicari, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Cappello, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia
Abstract: Spaceborne remote sensing techniques and numerical simulations have been combined in a web-GIS framework (LAV@HAZARD) to evaluate lava flow hazard in real time. By using the HOTSAT satellite thermal monitoring system to estimate time-varying TADR (time averaged discharge rate) and the MAGFLOW physicsbased
model to simulate lava flow paths, the LAV@HAZARD platform allows timely definition of parameters and maps essential for hazard assessment, including the propagation time of lava flows and the maximum run-out distance. We used LAV@HAZARD during the 2008–2009 lava flow-forming eruption at Mt Etna (Sicily, Italy). We measured the temporal variation in thermal emission (up to four times per hour) during the entire duration of the eruption using SEVIRI and MODIS data. The time-series of radiative power allowed us to identify six diverse thermal phases each related to different dynamic volcanic processes and associated
with different TADRs and lava flow emplacement conditions. Satellite-derived estimates of lava discharge rates were computed and integrated for the whole period of the eruption (almost 14 months), showing
that a lava volume of between 32 and 61 million cubic meters was erupted of which about 2/3 was emplaced during the first 4 months. These time-varying discharge rates were then used to drive MAGFLOW simulations
to chart the spread of lava as a function of time. TADRs were sufficiently low (b30 m3/s) that no lava flows were capable of flowing any great distance so that they did not pose a hazard to vulnerable (agricultural and urban) areas on the flanks of Etna.2011-12-31T23:00:00ZSAS multipass interferometry for monitoring seabed deformation using a high-frequency imaging sonar
http://hdl.handle.net/2122/7313
Title: SAS multipass interferometry for monitoring seabed deformation using a high-frequency imaging sonar
Authors: De Paulis, R.; ENI Exploration & Production Division – S. Donato Milanese, Italy; Prati, C.; DEI – Politecnico di Milano, Italy; Scirpoli, S.; DEI – Politecnico di Milano, Italy; Rocca, F.; DEI – Politecnico di Milano, Italy; Tesei, A.; NURC – La Spezia, Italy; Sletner, P. A.; NURC – La Spezia, Italy; Biagini, S.; NURC – La Spezia, Italy; Guerrini, P.; NURC – La Spezia, Italy; Gasparoni, F.; Tecnomare S.p.A – Marghera, Italy; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Locritani, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia
Abstract: Abstract-. This paper presents the results of a two years project led and funded by Eni from 2008 to 2010 with the aim of supporting
the development and experimentation of innovative technology for environmental monitoring. The problem addressed is the precise estimate of possible altimetric variations of the seabed through long-term monitoring. The selected methodology consists in the application of repeat-track interferometry to high-resolution, high-frequency sonar data collected from an AUV during repeated surveys of a seafloor area of interest. The paper describes the experimental measurements conducted at sea, the SAS and interferometry methodologies developed, and the results obtained on artificial objects sitting on the seabed. The quality of the achieved focusing is analyzed. The achieved repeat-pass SAS interferograms are shown and analyzed. The coherence along time of the particular
kind of seabed (silty sand) characterizing the experimental area is presented and the utility of artificial reflectors for long-term SAS interferometry is discussed.2011-07-31T22:00:00Z