Search results for "Physical model"
showing 10 items of 33 documents
A parsimonious dynamic model for river water quality assessment
2010
Water quality modelling is of crucial importance for the assessment of physical, chemical, and biological changes in water bodies. Mathematical approaches to water modelling have become more prevalent over recent years. Different model types ranging from detailed physical models to simplified conceptual models are available. Actually, a possible middle ground between detailed and simplified models may be parsimonious models that represent the simplest approach that fits the application. The appropriate modelling approach depends on the research goal as well as on data available for correct model application. When there is inadequate data, it is mandatory to focus on a simple river water qua…
Understanding the Effects of Fires on Surface Evapotranspiration Patterns Using Satellite Remote Sensing in Combination with an Energy Balance Model
2011
Forest fires are highly destructive for nature, affecting the landscape, the natural cicle of the vegetation, and the structure and functioning of ecosystems. Beyond that, they also provoke changes in the local and regional meteorology, and particularly in the surface energy flux patterns. In a fire-affected area, changes in the ecosystem structure and species composition modify the evapotranspiration (LE) and the rest of the terms involved in the energy balance equation. Besides, these changes in the local energy balance may persist for decades (Randerson et al., 2006). There is an increasing concern among the scientific community about the effect of forest fires on climate change at this …
Dry deposition models for radionuclides dispersed in air: a new approach for deposition velocity evaluation schema
2017
In the framework of a National Research Program funded by the Italian Minister of Economic Development, the Department of Energy, Information Engineering and Mathematical Models (DEIM) of Palermo University and ENEA Research Centre of Bologna, Italy is performing several research activities to study physical models and mathematical approaches aimed at investigating dry deposition mechanisms of radioactive pollutants. On the basis of such studies, a new approach to evaluate the dry deposition velocity for particles is proposed. Comparisons with literature experimental data show that the proposed dry deposition scheme allows to capture the main phenomena involved in the dry deposition process…
Exploiting the topographic information in a PDM-based conceptual hydrological model
2014
In this work, a conceptual lumped model was developed to simulate runoff and analyze hydrological processes with the goal of incorporating the morphological information into a probability-distributed model (PDM). PDMs usually describe the process of runoff generation as the result of soil saturation excess caused by precipitation with soil storage capacity represented by a spatially distributed quantity and described by a probability distribution. The proposed model, called topography-based probability distributed model (TOPDM), based on a simple water balance whose components are basin soil moisture storage, precipitation, drainage to groundwater, evapotranspiration, and Dunnian and Horton…
Conduit dynamics and post explosion degassing on Stromboli: A combined UV camera and numerical modeling treatment.
2016
Abstract Recent gas flux measurements have shown that Strombolian explosions are often followed by periods of elevated flux, or “gas codas,” with durations of order a minute. Here we present UV camera data from 200 events recorded at Stromboli volcano to constrain the nature of these codas for the first time, providing estimates for combined explosion plus coda SO2 masses of ≈18–225 kg. Numerical simulations of gas slug ascent show that substantial proportions of the initial gas mass can be distributed into a train of “daughter bubbles” released from the base of the slug, which we suggest, generate the codas, on bursting at the surface. This process could also cause transitioning of slugs i…
Mathematical models for the diffusion magnetic resonance signal abnormality in patients with prion diseases
2014
In clinical practice signal hyperintensity in the cortex and/or in the striatum on magnetic resonance (MR) diffusion-weighted images (DWIs) is a marker of sporadic Creutzfeldt–Jakob Disease (sCJD). MR diagnostic accuracy is greater than 90%, but the biophysical mechanisms underpinning the signal abnormality are unknown. The aim of this prospective study is to combine an advanced DWI protocol with new mathematical models of the microstructural changes occurring in prion disease patients to investigate the cause of MR signal alterations. This underpins the later development of more sensitive and specific image-based biomarkers. DWI data with a wide a range of echo times and diffusion weightin…
Numerical simulation of heat transfer, fluid flow and elements diffusion during laser welding of dissimilar steels
2017
The design of new steel grades offering equivalent mechanical performances for lower thicknesses and the added value with the possibility to join two different steel grades, require development and control of joining processes. Thanks to high precision and good flexibility, the laser welding became one of the most used processes for joining of dissimilar welded blanks. The prediction of local chemical composition in the weld formed between dissimilar steels in function of the welding parameters is essential because the dilution rate and the distribution of alloying elements in the melted zone determine the final tensile strength of the weld. The goal of the present study is to create and to…
GPR multi-component data analysis
2007
In order to test the capabilities of ground-penetrating radar (GPR) detection, models were reproduced in a laboratory using both plastic and metal cylinders as well as sheets to represent anomalies buried in a plastic tank containing sand. These models, which represent pipes and dipping layers in a homogeneous medium (i.e., sand), were used to detect the object’s position and study its polarization properties based on the different dielectric contrasts between the object and the surrounding medium. We paid particular attention to the choice of medium through which the wavefield propagated, to be sure of its isotropy and homogeneity, in order for the velocity to be the same for every path tr…
Stochastic seismic analysis of hydrodynamic pressure in dam reservoir systems
2002
Hydrodynamic seismic-induced pressure requires careful consideration in the aseismic design of dams. Effects induced by earthquake excitation may cause many-fold increments of hydrostatic pressure. In this study earthquake excitation has been modelled by means of random process theory obtaining the response statistics of a dam-reservoir dynamical system. The analysis has been conducted assuming a rigid retaining wall of the reservoir and dissipative fluid. Copyright © 2002 John Wiley & Sons, Ltd.
Modelling systems of classical/quantum identical particles by focusing on algorithms
2012
A procedure modelling ideal classical and quantum gases is discussed. The proposed approach is mainly based on the idea that modelling and algorithm analysis can provide a deeper understanding of particularly complex physical systems. Appropriate representations and physical models able to mimic possible pseudo-mechanisms of functioning and having predictive validity are developed.