Search results for "Numerical models"
showing 10 items of 38 documents
Controlled time integration for the numerical simulation of meteor radar reflections
2016
We model meteoroids entering the Earth[U+05F3]s atmosphere as objects surrounded by non-magnetized plasma, and consider efficient numerical simulation of radar reflections from meteors in the time domain. Instead of the widely used finite difference time domain method (FDTD), we use more generalized finite differences by applying the discrete exterior calculus (DEC) and non-uniform leapfrog-style time discretization. The computational domain is presented by convex polyhedral elements. The convergence of the time integration is accelerated by the exact controllability method. The numerical experiments show that our code is efficiently parallelized. The DEC approach is compared to the volume …
Effects of different boundary conditions and palaeotopographies on the onshore response of tsunamis in a numerical model – A case study from western …
2016
Abstract Hydrodynamic numerical models are essential in modern tsunami hazard assessment. They allow the economical simulation of possible tsunami scenarios for areas at risk and provide reliable and detailed insights into local onshore dynamics. This is especially true when simulations are calibrated with field traces of past tsunami inundation events. Following this approach, the current study focuses on palaeotsunami events indicated by sedimentary and geomorphological field traces in the northern Gulf of Kyparissia (NW Greece). Based on three different digital elevation models (DEM) – reflecting the recent and two palaeotopographies – various tsunami wave constellations according to the…
The Impact of a Very Weak and Thin Upper Asthenosphere on Subduction Motions
2019
Recent geophysical observations report the presence of a very weak and thin upper asthenosphere underneath subducting oceanic plates at convergent margins. Along these margins, trench migrations are significantly slower than plate convergence rates. We use numerical models to assess the role of a weak upper asthenospheric layer on plate and trench motions. We show that the presence of this layer alone can enhance an advancing trend for the motion of the plate and hamper trench retreat. This mechanism provides a novel and alternative explanation for the slow rates of trench migration and fast-moving plates observed globally at natural subduction zones.
Electromechanical Numerical Analysis of an Air-Core Pulsed Alternator via Equivalent Network Formulation
2017
In this paper, the numerical analysis on an air-core pulsed alternator is presented. Since compulsators are characterized by very fast electromechanical transients, their accurate analysis requires strong coupling between the equations governing the electrical and the mechanical behaviors. The device is investigated by using a dedicated numerical code capable to take into account eddy currents, compensating windings, as well as the excitation/control circuits. Furthermore, the code is capable of modeling centrifugal forces and vibrations acting on the shaft due to electric and mechanical unbalances or to misalignments of the shaft from its centered position. This makes the code a very power…
Numerical-Analytical Model for Nanotube-Reinforced Nanocomposites
2013
A novel numerical model able to predict the elastic properties of carbon nanotube/polymer composites containing a random distribution of CNTs has been developed. The new technique, which takes into account of the curvature that the nanotubes show when immersed in the polymer, is based on a numerical-analytical approach that has significant advances over micromechanical modeling and can be applied to several kinds of nanostructured composites. The nature of carbon nanotube/polymer bonding has arisen as key factor in the efficacy of the carbon nanotubes to actually provide any enhanced stiffness or strength to the composite. Here the effects of carbon nanotube interface interaction with the m…
The effect of through-thickness compressive stress on mode II interlaminar fracture toughness
2017
Abstract The effect of through-thickness compressive stress on mode II interlaminar fracture toughness is investigated experimentally and replicated numerically. The modified Transverse Crack Tensile specimen recently proposed by the authors is used, together with an experimental device designed to apply a constant transverse compressive stress on the surface of the specimen. Experiments are conducted using IM7/8552 specimens for different compressive stresses, ranging from 0 to 100 MPa, covering all the practical applications commonly encountered in the aeronautical industry (e.g., tightened filled holes or bolted joints). It is shown that mode II interlaminar fracture toughness increases …
ECOHYDROLOGICAL MODELLING IN MEDITERRANEAN AREAS AND WETLANDS
2010
La seguente dissertazione verte sul campo di ricerca noto come Ecoidrologia. Sebbene tale scienza, che studia le mutue interazioni fra ciclo idrologico e gli ecosistemi naturali, sia stata recentemente oggetto di svariati studi, alcuni dei suoi numerosi aspetti rimangono tuttavia ancora alquanto inesplorati. L’obiettivo principale della presente tesi è quello di rivisitare la letteratura scientifica esistente sull’argomento, cercando di adattare concetti e modelli sviluppati per certi ecosistemi anche alle peculiarità di altri ambienti meno studiati, come quelli aridi e semiaridi tipici della zona Mediterranea o le cosiddette “wetlands”, zone umide e paludose. In particolare, viene approfon…
Inspection of additive-manufactured layered components
2015
Laser powder deposition (LPD) is a rapid additive manufacturing process to produce, layer upon layer, 3D geometries or to repair high-value components. Currently there is no nondestructive technique that can guarantee absence of flaws in LPD products during manufacturing. In this paper a laser ultrasonic technique for in-line inspection of LPD components is proposed. Reference samples were manufactured from Inconel and machined flaws were created to establish the sensitivity of the technique. Numerical models of laser-generated ultrasonic waves have been created to gain a deeper understanding of physics, to optimize the set-up and to verify the experimental measurements. Results obtained on…
Machine learning information fusion in Earth observation: A comprehensive review of methods, applications and data sources
2020
This paper reviews the most important information fusion data-driven algorithms based on Machine Learning (ML) techniques for problems in Earth observation. Nowadays we observe and model the Earth with a wealth of observations, from a plethora of different sensors, measuring states, fluxes, processes and variables, at unprecedented spatial and temporal resolutions. Earth observation is well equipped with remote sensing systems, mounted on satellites and airborne platforms, but it also involves in-situ observations, numerical models and social media data streams, among other data sources. Data-driven approaches, and ML techniques in particular, are the natural choice to extract significant i…