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Papers by berardi sensale

RILEM Bookseries, 2021

This editorial refers to 'Low dose rivaroxaban and aspirin among patients with peripheral artery ... more This editorial refers to 'Low dose rivaroxaban and aspirin among patients with peripheral artery disease: a meta-analysis of the COMPASS and VOYAGER trials', by S.S. Anand et al., pp. e181-e189.

Structural and Multidisciplinary Optimization, 2004

A numerical evolutionary procedure for the structural optimisation for stress reduction of twodim... more A numerical evolutionary procedure for the structural optimisation for stress reduction of twodimensional structures is presented in this paper. The proposed procedure couples the biological growth method (BGM) with the boundary element method (BEM). The boundary-only intrinsic characteristic of BEM together with its accuracy in the boundary displacement and stress solutions make BEM especially attractive for solving shape-optimisation problems. Two formulations of BEM are used in this work: the standard for two-dimensional elastostatics for the stress analysis and the dual reciprocity method (DRM), which is used to model the swelling or shrinking of the material. Two examples are analysed to illustrate the proposed methodology and to demonstrate its versatility and robustness.

Computational Mechanics, 2002

The placement of source points constitutes a key issue for the method of the fundamental solutio... more The placement of source points constitutes a key issue for the method of the fundamental solutions. In particular, for problems with singularities of any kind the determination of the optimal placement of source points becomes relevant, as no linear combination of arbitrarily located source points can guarantee a reasonable approximation to the solution. This paper investigates the use of a “Simulated Annealing” algorithm in the optimal placement of source points in singular problems. The algorithm is essentially an iterative random search with adaptive moves along the coordinate directions. It permits uphill moves under the control of a probabilistic criterion, thus tending to avoid the first local minima encountered. The proposed methodology is employed with a variety of test problems. Results are compared to those of an analytical optimisation routine and their relatively merits and disadvantages discussed. Simulated annealing is shown to be an attractive option for the optimisation of singular problems, with a high rate of success, and able to solve problems for which analytical optimisation routines fail.

Aeu-international Journal of Electronics and Communications, 2008

In this paper a procedure based on the hypersingular element method is applied to find the TE and... more In this paper a procedure based on the hypersingular element method is applied to find the TE and TM modes in arbitrarily shaped waveguides. To show the accuracy of this method, various examples are solved and the results are compared to those analytical, when there is an analytical solution, and those presented in the literature. The proposed method did not

International Journal of Numerical Modelling-electronic Networks Devices and Fields, 2008

The method of fundamental solutions (MFS) is proposed for the analysis of microstrip patch antenn... more The method of fundamental solutions (MFS) is proposed for the analysis of microstrip patch antennas of arbitrary shape. The MFS consists mainly in approximating the solution of a problem by a linear combination of known fundamental solutions associated with source points located outside the domain. The implementation of the MFS is simple and computationally efficient. Simulation results are obtained for rectangular, circular and triangular microstrip patch antennas. The resonance frequency and input impedance results are in good agreement with those published in the literature. Two prototypes have been fabricated and tested. Good agreement has been obtained between the MFS simulations and the experimental results.

Engineering Analysis With Boundary Elements

ABSTRACT A boundary element method based on the convolution quadrature method for the numerical s... more ABSTRACT A boundary element method based on the convolution quadrature method for the numerical solution of uncoupled transient thermoelasticity problems is presented. In the proposed formulation, the time-domain integral equation is numerically approximated by a quadrature formula whose weight factors are computed by means of integral expressions involving the Laplace transform of the fundamental solution. Compared with other numerical methods that operate directly in the Laplace transformed domain, the proposed formulation requires only the definition of the time-step used by the procedure of integration, and does not need special techniques of inversion from the Laplace-domain to the time-domain. Numerical examples of transient thermoelasticity problems are presented to show the versatility and accuracy of the method.

Engineering Analysis With Boundary Elements, 2010

The boundary knot method is a promising meshfree, integration-free, boundary-type technique for t... more The boundary knot method is a promising meshfree, integration-free, boundary-type technique for the solution of partial differential equations. It looks for an approximation of the solution in the linear span of a set of specialized radial basis functions that satisfy the governing equation of the problem. The boundary conditions are taken into account through the collocation technique. The specialized radial basis function for harmonic elastic and viscoelastic problems is derived, and a boundary knot method for the solution of these problems is proposed. The completeness issue regarding the proposed set of radial basis functions is discussed, and a formal proof of incompleteness for the circular ring problem is presented. In order to address the numerical performance of the proposed method, some numerical examples considering simple and complex domains are solved.

International Journal for Numerical Methods in Engineering, 2001

ABSTRACT A general boundary element formulation for the stress analysis of bodies with ageing vis... more ABSTRACT A general boundary element formulation for the stress analysis of bodies with ageing viscoelastic constitutive relations such as concrete or biological materials is presented. It is shown that in the case of a constant Poisson modulus, the domain integral vanishes. Otherwise, the domain integrals are taken to the boundary by means of the dual reciprocity method. Computational details and examples are given. Copyright © 2001 John Wiley & Sons, Ltd.

Engineering Analysis With Boundary Elements, 2000

The method of fundamental solutions (MFS), ®rst proposed in the 1960s, has recently reappeared in... more The method of fundamental solutions (MFS), ®rst proposed in the 1960s, has recently reappeared in the literature and solutions of an extraordinary accuracy have been reported using relatively few data points. The method requires no mesh and therefore no integration, and has been recently combined with dual reciprocity method (DRM) for treating inhomogeneous terms. The objective of this paper is the combination of the two methods for treating convective terms which are derivatives of the problem variable. First the formulation of the methods for mixed Neumann±Dirichlet boundary conditions is considered, as both these types of boundary condition are necessary for this type of problem. Next a formulation for the usual Crank±Nickleson and Galerkin time-stepping procedures is obtained for both diffusion and diffusion±convection and the use of the subdomain technique with MFS is considered. Finally results obtained for some test problems are presented including a diffusion convection problem with variable velocity using both a single domain and a division into subregions, the convective terms being modeled using DRM. Results are compared with exact solutions and in some cases with DRBEM examples from the literature. q

Communications in Numerical Methods in Engineering, 1997

on the radial basis function (RBF), nonsingular general solution, and dual reciprocity method (DR... more on the radial basis function (RBF), nonsingular general solution, and dual reciprocity method (DRM), this paper presents an inherently meshless, integration-free, boundaryonly RBF collocation technique for numerical solution of various partial differential equation systems. The basic ideas behind this methodology are very mathematically simple. In this study, the RBFs are employed to approximate the inhomogeneous terms via the DRM, while nonsingular general solution leads to a boundary-only RBF formulation for homogenous solution. The present scheme is named as the boundary knot method (BKM) to differentiate it from the other numerical techniques.