1,721,189 research outputs found
Eigenvalue distribution of constraint-preconditioned symmetric saddle point matrices
No full textThis paper is devoted to the analysis of the eigenvalue distribution of two classes of block preconditioners
for the generalized saddle point problem. Most of the bounds developed improve those of previous published works.
Numerical results onto a realistic test problem give evidence of the effectiveness of the estimates on the spectrum
of preconditioned matrices
Block preconditioners for linear systems in interior point methods for convex constrained optimization
Full text linkParallel Newton methods for sparse systems of nonlinear equations
No full textA parallel code based on Cimmino-like preconditioner is developed for the solution of the Newton linearized system
Numerical comparison of iterative eigensolvers for large sparse symmetric matrices
No full textThe Jacobi-Davidson (JD) method has been recently proposed
for the evaluation of the partial eigenspectrum of large sparse
matrices. In this work we report a set of numerical experiments
that compare this method with other previously
proposed techniques; DACG (Deflation Accelerated Conjugate Gradient)
and Lanczos (ARPACK), on large sparse symmetric matrices.
The results obtained by JD and DACG are benchmarked against
those obtained with ARPACK in terms ofcomputational time for the evaluation of a number of the leftomost eigenpairs
of large and sparse matrice
Mixed Finite Elements and Newton-type Linearization for the Solution of Richard's Equation
No full textWe present the development of a two-dimensional Mixed-Hybrid Finite Element (MHFE) model for the solution of the non-linear equation of variably saturated flow in groundwater on unstructured triangular meshes. By this approach the Darcy velocity is approximated using lowest-order Raviart-Thomas (RT0) elements and is 'exactly' mass conserving. Hybridization is used to overcome the ill-conditioning of the mixed system. The scheme is globally first-order in space. Nevertheless, numerical results employing non-uniform meshes show second-order accuracy of the pressure head and normal fluxes on specific grid points. The non-linear systems of algebraic equations resulting from the MHFE discretization are solved using Picard or Newton iterations. Realistic sample tests show that the MHFE-Newton approach achieves fast convergence in many situations, in particular, when a good initial guess is provided by either the Picard scheme or relaxation technique
Le Corbusier al bastione Kellermann di Parigi. L'Architettura dimostrativa della nuova città
No full textIl lavoro di ricerca svolto all’interno del Dottorato in Composizione architettonica coglie l’occasione di rileggere una pagina dell’intensa opera architettonica di una delle figure più rilevanti del Movimento Moderno per evidenziarne il grado di unicità che questa rappresenta all’interno dell’opera lecorbuseriana.
Il progetto per il bastione Kellermann di Parigi del 1935 diviene architettura "inaspettata" in cui Le Corbusier si spinse per la prima volta ad un dialogo con la storia del luogo, mostrando il processo di costruzione dell’edificio come momento di verifica e dimostrazione di una serie di principi che aveva elaborato e teorizzato negli anni precedenti.
Il caso-studio diviene punto di partenza per avviare una riflessione sull’architettura, poiché inserito in un ciclo di progetti rappresentanti un vero e proprio laboratorio di sperimentazioni progettuali che assumono un ruolo decisivo per comprendere il lavoro operato dall’Architetto sui temi che concorrono alla costruzione di una nuova idea di città, nella sua dimensione fisica e politica
Mixed finite elements for the solution of Richard's equation
No full textWe present a two-dimensional mixed finite element model of variably saturated flow on unsaturated triangular meshes. Velocities are approximated using the lowest order Raviart-Thomas (RT0) elements with piecewise constant pressure. The resulting nonlinear systems of algebraic equations are solved using Picard iterations in combination with ad hoc preconditioning techniques to improve the convergence of the conjugate gradient method in the solution of the linearized mixed system. The MFE scheme with Picard linearizations is tested on a sample test and compared with the Galerkin Finite Element formulation. The comparison is carried out in terms of convergence of the nonlinear and linear solvers, and computational efficiency
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