1,720,963 research outputs found
Stima dell'allagamento della piana a Sud di Latisana (sinistra Tagliamento) mediante modellazione matematica bidimensionale
No full textIl metodo delle celle nella meccanica dei fluidi:un'applicazione alle equazioni in acque basse
No full textStime dell'allagamento della piana a sud di Latisana (sinistra Tagliamento) mediante modellazione matematica bidimensionale
No full textVALUTAZIONE DELLA PERMEABILITA’ MEDIANTE APPROCCIO NETWORK MODELING
No full textVALUTAZIONE DELLA PERMEABILITA’ MEDIANTE APPROCCIO NETWORK MODELING
C.Marson1, V.Fiorotto 1, L.Zovatto 1
(1) Dipartimento di Ingegneria Civile ed Ambientale, Università degli Studi di Trieste, P.le Europa 1, 34127, Trieste - e-mail: [email protected]
La nota analizza la possibilità offerta dal network-modeling, ossia la ricostruzione della struttura dei vuoti interni alla matrice solida di un ammasso poroso e la rappresentazione di essi mediante una rete di tubi capillari, per la valutazione della permeabilità. Il procedimento, mediante l’ integrazione delle equazioni di Navier-Stokes all’interno dei canalicoli, permette di determinare la portata filtrante e di conseguenza, tramite la legge di Darcy, la permeabilità. Il metodo è stato applicato alla ricostruzione di campioni di terreno i cui grani sono stati approssimati da sfere generate casualmente. I risultati ottenuti sono stati confrontati con i dati sperimentali reperibili in letteratura e con i risultati ottenibili dalle formule empiriche più comuni osservando che il metodo proposto può rappresentare un’estensione di queste nelle pratiche applicazioni potendo tener conto di un maggior numero di parametri
Improving the convergence order of the meshless approach for the Cell Method for numerical integration of discrete conservation laws
No full textIn thiswork, the problem of increasing the convergence order of
the integral meshless method already proposed by the same authors
is addressed. Solutions are determined through equations directly
written in discrete form over a tributary region represented by the
circle with center in the generic node and radius given by the average
of the distances between the node itself and its neighbors,
thus allowing a considerable ease in writing the discrete form of
the governing equations. The proposed approach, besides avoiding
global mesh generation, adopts interpolating polynomials, which
exactly reproduce nodal values of field variables, and eliminates
some problems typically encountered when posing Dirichlet and
Neumann boundary conditions with the Finite Element Method.
Several numerical schemes adopting extended or compact computational
cells are proposed and tested for the Laplace equation, in
line with the previous papers. Results show that, when using interpolating
polynomials that satisfy also the differential operator
in some nodes, compact computational cells characterized by the
fifth-order of convergence may be constructed
Optimal location and control of pressure reducing valves in water networks
No full textThis paper addresses the problem of optimal pressure management in water distribution systems through the introduction and
regulation of pressure reducing valves. Reduction in pressure is aimed at controlling water leakages which, being in some cases a high
proportion of the total volume supplied, are nowadays one of the major concerns for water utilities. The determination of the number,
location, and setting of such valves is formulated as a two criteria optimization problem and is solved with multiobjective genetic
algorithms. In particular, the first criterion is represented by the minimization of the number of valves, and the second is the minimization
of the total leakage in the system, when maintaining the required pressure at each node. The great advantage of the multiobjective
approach resides in the fact that, in one run, several trade-off alternatives are found, thus providing the set of the optimal solutions with
a different level of compromise between the conflicting objectives. At the same time, data necessary for practical choice and operation of
pressure reducing valves may be determined
Extension of the meshless approach for the Cell Method to three-dimensional numerical integration of discrete conservation laws
No full textThe meshless approach for the Cell Method: a new way for the numerical solution of discrete conservation laws
No full text
Integration between volumetric change and strain for describing the global mechanical function of the left ventricle
No full textIntroduction: Evaluations of left ventricular systolic function based on ejection fraction (EF) alone are unable to recognize impaired myocardial performance in some dysfunctional states, and strain parameters are often invoked for an improved description of cardiac contraction. A comprehensive framework integrating deformation measures with volumetric changes is therefore necessary. Methods: This study presents a general mathematical background that confirms and generalizes a previously proposed framework relating volumetric changes and strain values. The model is then validated with 5450 data samples made of LV volume, global longitudinal strain (GLS) and global circumferential strain (GCS) from 109 heterogeneous subjects who underwent cardiac magnetic resonance imaging. The GCS was measured by either three short-axis slices or 3D LV geometry reconstructed from 3 long-axis slices. Results: Results demonstrated the reliability of the relationship EF = 1 − (GLS + 1)(GCS + 1)2. Accuracy is higher (correlation coefficient r = 0.997) when GCS is obtained by 3D deformation, although it remains high (r = 0.98) when GCS is measured from short-axis slices. However, the latter may underestimate (about 10% in relative terms) the circumferential deformation due to through-plane motion. Conclusions: The accuracy of this relationship permits a unitary description of LV systolic function in terms of both EF and global strain values by its position on the strain plane (GLS, GCS). This also allows to monitor pathologic or healing changes, as a consequence of exercise, drugs, surgery or other therapeutic options, as trajectories on that plane
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