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2017 Software Open Access

NOSA-ITACA 1.1
Binante V., Girardi M., Padovani C., Pasquinelli G., Pellegrini D., Porcelli M., Robol L.
NOSA-ITACA is a code for the nonlinear structural analysis of historical masonry constructions. It the result of the integration of the finite element code NOSA into the open-source SALOME platform.

See at: ISTI Repository Open Access | CNR ExploRA | www.nosaitaca.it

2019 Contribution to conference Open Access

FE model updating of the Matilde donjon in Livorno
Azzara R. M., Girardi M., Padovani C., Pellegrini D., Robol L.
The paper describes a preliminary experimental campaign conducted on The Matilde donjon in Livorno (Italy) aimed to characterize its dynamic behaviour, and the corresponding numerical analysis conducted on a FE model created via the NOSA-ITACA code.Source: CIVIL-COMP 2019, Riva del Garda Italy, 16-19/09/2019

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2017 Conference article Restricted

NOSA-ITACA: a free FE program for historic masonry buildings
Girardi M., Padovani C., Pellegrini D., Robol L.
This paper describes the main features of NOSA-ITACA, a finite-element code for the structural analysis of masonry constructions of historical interest and reports on its application to the structural analysis of some historic buildings in Italy.Source: ECCOMAS Conference on Recent Advances in Nonlinear Models - Design and Rehabilitation of Structures, pp. 43–52, Coimbra, Portugal, 16-17/1172017

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2018 Report Unknown

Progetto TITANIO - Sensori innovativi per il monitoraggio del patrimonio architettonico. Rapporto sull'attività svolta nel periodo 19 Agosto 2017 - 19 Agosto 2018
Azzara R. M., Barsocchi P., Cassarà P., Girardi M., Lucchesi D., Mavilia F., Padovani C., Pellegrini D., Robol L.
Il documento descrive le attività conclusive del progetto TITANIO (Sensori innovativi per il monitoraggio del patrimonio architettonico), finanziato dalla Fondazione Carilucca per il biennio 2016-2018.Source: Project report, TITANIO, 2018

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2019 Report Unknown

MOSCARDO - Tecnologie ICT per il MOnitoraggio Strutturale di Costruzioni Antiche basato su Reti di sensori wireless e DrOni [MMS Lab, Rapporto tecnico n. 2]
Girardi M., Padovani C., Pellegrini D., Robol L.
MOSCARDO - ICT technologies for structural monitoring of age-old constructions based on wireless sensor networks and drones. Description of the activities conducted by the Mechanics of Materials and Structures Laboratory of ISTI-CNR. Project Report n. 2.Source: Project report, MOSCARDO, 2019

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2019 Conference article Open Access

Nonlinear FE model updating for masonry constructions via linear perturbation and modal analysis
Girardi M., Padovani C., Pellegrini D., Robol L.
This paper describes the automated nonlinear model updating procedure for ma-sonry structures implemented in the NOSA-ITACA code. The algorithm, aimed at matchingnumerical and experimental natural frequencies and mode shapes, combines nonlinear staticanalysis, linear perturbation and modal analysis and allows fine-tuning the free parametersof the model. The numerical method is applied to two simple case studies, which prove itseffectiveness.Source: COMPDYN 2019, Crete, Greece, 24-26/06/2019

See at: 2019.compdyn.org Open Access | ISTI Repository | CNR ExploRA

2020 Journal article Open Access

Computing performability measures in Markov chains by means of matrix functions
Masetti G., Robol L.
We discuss the efficient computation of performance, reliability, and availability measures for Markov chains; these metrics - and the ones obtained by combining them, are often called performability measures. We show that this computational problem can be recasted as the evaluation of a bilinear form induced by appropriate matrix functions, and thus solved by leveraging the fast methods available for this task.Source: Journal of computational and applied mathematics 368 (2020). doi:10.1016/j.cam.2019.112534
DOI: 10.1016/j.cam.2019.112534
DOI: 10.48550/arxiv.1803.06322
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2018 Journal article Open Access

Corrigendum to "Solvability and uniqueness criteria for generalized Sylvester-type equations"
De Teran F., Iannazzo B., Poloni F., Robol L.
We provide an amended version of Corollaries 7 and 9 in [De Teran, Iannazzo, Poloni, Robol, "Solvability and uniqueness criteria for generalized Sylvester-type equations"]. These results characterize the unique solvability of the matrix equation AXB + CX*D = E (where the coefficients need not be square) in terms of an equivalent condition on the spectrum of certain matrix pencils of the same size as one of its coefficients. (C) 2017 Elsevier Inc. All rights reserved.Source: Linear algebra and its applications 542 (2018): 522–526. doi:10.1016/j.laa.2017.10.018
DOI: 10.1016/j.laa.2017.10.018
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See at: Linear Algebra and its Applications Open Access | ISTI Repository | www.sciencedirect.com Restricted | CNR ExploRA

2018 Journal article Open Access

Solvability and uniqueness criteria for generalized Sylvester-type equations
De Teran F., Iannazzo B., Poloni F., Robol L.
We provide necessary and sufficient conditions for the generalized (star operator)-Sylvester matrix equation, AXB+CX(star operator)D=E, to have exactly one solution for any right-hand side E. These conditions are given for arbitrary coefficient matrices A, B, C, D (either square or rectangular) and generalize existing results for the same equation with square coefficients. We also review the known results regarding the existence and uniqueness of solution for generalized Sylvester and (star operator)-Sylvester equations.Source: Linear algebra and its applications 542 (2018): 501–521. doi:10.1016/j.laa.2017.07.010
DOI: 10.1016/j.laa.2017.07.010
DOI: 10.48550/arxiv.1608.01183
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2018 Conference article Open Access

Fea for masonry structures and vibration-based model updating using NOSA-ITACA
Girardi M., Padovani C., Pellegrini D., Porcelli M., Robol L.
NOSA-ITACA is a finite-element code developed by the Mechanics of Materials and Structures Laboratory of ISTI-CNR for the structural analysis of masonry constructions of historical interest via the constitutive equation of masonry-like materials. The latest improvements in the software allow applying model updating techniques to match experimentally measured frequencies in order to fine-tune calculation of the free parameters in the model. The numerical method is briefly presented and applied to two historical buildings in Lucca, the Church of San Francesco and the Clock Tower.Source: 10th International Masonry Conference, pp. 723–735, Milano, Italy, 9-11 July 2018

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2018 Report Open Access

Analyzing a security and reliability model using Krylov methods and matrix functions
Masetti G., Robol L.
It has been recently shown how the computation of performability measures for Markov models can be recasted as the evaluation of a bilinear forminduced by appropriate matrix functions. In view of these results, we show how to analyze a security model, inspired by a real world scenario. The model describes a mobile cyber-physical system of communicating nodes which are subject to security attacks. We take advantage of the properties of matrix functions of block matrices, and provide efficient evaluation methods.Moreover, we show how this new formulation can be used to retrieve interesting theoretical results, which can also rephrased in probabilistic terms.Source: ISTI Technical reports, 2018

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2018 Journal article Open Access

Model parameter estimation using Bayesian and deterministic approaches: the case study of the Maddalena Bridge
De Falco A., Girardi M., Pellegrini D., Robol L., Sevieri G.
Finite element modeling has become common practice for assessing the structural health of historic constructions. However, because of the uncertainties typically affecting our knowledge of the geometrical dimensions, material properties and boundary conditions, numerical models can fail to predict the static and dynamic behavior of such structures. In order to achieve more reliable predictions, important information can be obtained measuring the structural response under ambient vibrations. This wholly non-destructive technique allows obtaining very accurate information on the structure's dynamic properties (Brincker and Ventura (2015)).Source: Procedia structural integrity 11 (2018): 210–217. doi:10.1016/j.prostr.2018.11.028
DOI: 10.1016/j.prostr.2018.11.028
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See at: Procedia Structural Integrity Open Access | ISTI Repository | www.sciencedirect.com | CNR ExploRA

2019 Journal article Open Access

Model updating procedure to enhance structural analysis in FE Code NOSA-ITACA
Girardi M., Padovani C., Pellegrini D., Robol L.
This paper describes a model updating procedure implemented in NOSA-ITACA, a finite-element (FE) code for the structural analysis of masonry constructions of historical interest. The procedure, aimed at matching experimental frequencies and mode shapes, allows for fine-tuning the calculations of the free parameters in the model. The numerical method is briefly described, and some issues related to its robustness are addressed. The procedure is then applied to a simple case study and two historical structures in Tuscany, the Clock Tower in Lucca and the Maddalena Bridge in Borgo a Mozzano.Source: Journal of performance of constructed facilities 33 (2019): 04019041-1–04019041-16. doi:10.1061/(ASCE)CF.1943-5509.0001303
DOI: 10.1061/(asce)cf.1943-5509.0001303
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See at: Journal of Performance of Constructed Facilities Open Access | ISTI Repository | ascelibrary.org Restricted | Journal of Performance of Constructed Facilities | CNR ExploRA

2019 Journal article Open Access

Nonsingular systems of generalized Sylvester equations: An algorithmic approach
De Teran F., Iannazzo B., Poloni F., Robol L.
We consider the uniqueness of solution (i.e., nonsingularity) of systems of r generalized Sylvester and -Sylvester equations with nxn coefficients. After several reductions, we show that it is sufficient to analyze periodic systems having, at most, one generalized -Sylvester equation. We provide characterizations for the nonsingularity in terms of spectral properties of either matrix pencils or formal matrix products, both constructed from the coefficients of the system. The proposed approach uses the periodic Schur decomposition and leads to a backward stable O(n(3)r) algorithm for computing the (unique) solution.Source: Numerical linear algebra with applications 26 (2019). doi:10.1002/nla.2261
DOI: 10.1002/nla.2261
DOI: 10.48550/arxiv.1709.03783
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2020 Journal article Open Access

Rational Krylov and ADI iteration for infinite size quasi-Toeplitz matrix equations
Robol L.
We consider a class of linear matrix equations involving semi-infinite matrices which have a quasi-Toeplitz structure. These equations arise in different settings, mostly connected with PDEs or the study of Markov chains such as random walks on bidimensional lattices. We present the theory justifying the existence of the solution in an appropriate Banach algebra which is computationally treatable, and we propose several methods for computing them. We show how to adapt the ADI iteration to this particular infinite dimensional setting, and how to construct rational Krylov methods. Convergence theory is discussed, and numerical experiments validate the proposed approaches.Source: Linear algebra and its applications 604 (2020): 210–235. doi:10.1016/j.laa.2020.06.013
DOI: 10.1016/j.laa.2020.06.013
DOI: 10.48550/arxiv.1907.02753
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2018 Journal article Open Access

Efficient Ehrlich-Aberth iteration for finding intersections of interpolating polynomials and rational functions
Robol L., Vandebril R.
We analyze the problem of carrying out an efficient iteration to approximate the eigenvalues of some rank structured pencils obtained as linearization of sums of polynomials and rational functions expressed in (possibly different) interpolation bases. The class of linearizations that we consider has been introduced by Robol, Vandebril and Van Dooren in [17]. We show that a traditional QZ iteration on the pencil is both asymptotically slow (since it is a cubic algorithm in the size of the matrices) and sometimes not accurate (since in some cases the deflation of artificially introduced infinite eigenvalues is numerically difficult). To solve these issues we propose to use a specifically designed Ehrlich-Aberth iteration that can approximate the eigenvalues in O(kn²) flops, where k is the average number of iterations per eigenvalue, and n the degree of the linearized polynomial. We suggest possible strategies for the choice of the initial starting points that make k asymptotically smaller than O(n), thus making this method less expensive than the QZ iteration. Moreover, we show in the numerical experiments that this approach does not suffer of numerical issues, and accurate results are obtained.Source: Linear algebra and its applications 542 (2018): 282–309. doi:10.1016/j.laa.2017.05.010
DOI: 10.1016/j.laa.2017.05.010
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2019 Report Open Access

ISTI Young Researcher Award "Matteo Dellepiane" - Edition 2019
Barsocchi P., Candela L., Crivello A., Esuli A., Ferrari A., Girardi M., Guidotti R., Lonetti F., Malomo L., Moroni D., Nardini F. M., Pappalardo L., Rinzivillo S., Rossetti G., Robol L.
The ISTI Young Researcher Award (YRA) selects yearly the best young staff members working at Institute of Information Science and Technologies (ISTI). This award focuses on quality and quantity of the scientific production. In particular, the award is granted to the best young staff members (less than 35 years old) by assessing their scientific production in the year preceding the award. This report documents the selection procedure and the results of the 2019 YRA edition. From the 2019 edition on the award is named as "Matteo Dellepiane", being dedicated to a bright ISTI researcher who prematurely left us and who contributed a lot to the YRA initiative from its early start.Source: ISTI Technical reports, 2019

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2017 Journal article Open Access

Fast Hessenberg reduction of some rank structured matrices
Gemignani L., Robol L
We develop two fast algorithms for Hessenberg reduction of a structured matrix $A = D + UV^H$, where $D$ is a real or unitary n x n diagonal matrix and $U, V in mathbb{C}^{n times k}$. The proposed algorithm for the real case exploits a two-stage approach by first reducing the matrix to a generalized Hessenberg form and then completing the reduction by annihilation of the unwanted subdiagonals. It is shown that the novel method requires O(n^2 k) arithmetic operations and is significantly faster than other reduction algorithms for rank structured matrices. The method is then extended to the unitary plus low rank case by using a block analogue of the CMV form of unitary matrices. It is shown that a block Lanczos-type procedure for the block tridiagonalization of Re(D) induces a structured reduction on A in a block staircase CMV-type shape. Then, we present a numerically stable method for performing this reduction using unitary transformations and show how to generalize the subdiagonal elimination to this shape, while still being able to provide a condensed representation for the reduced matrix. In this way the complexity still remains linear in k and, moreover, the resulting algorithm can be adapted to deal efficiently with block companion matrices.Source: SIAM journal on matrix analysis and applications (Print) 38 (2017): 574–598. doi:10.1137/16M1107851
DOI: 10.1137/16m1107851
DOI: 10.48550/arxiv.1612.04196
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2018 Journal article Open Access

On quadratic matrix equations with infinite size coefficients encountered in QBD stochastic processes
Bini D. A., Massei S., Meini B., Robol L.
Matrix equations of the kind $A_1 X^2 + A0 X + A_{-1} = X$, where both the matrix coefficients and the unknown are semi-infinite matrices belonging to a Banach algebra, are considered. These equations, where coefficients are quasi-Toeplitz matrices, are encountered in certain quasi-birth-death processes as the tandem Jackson queue or in any other processes that can be modeled as a reflecting random walk in the quarter plane. We provide a numerical framework for approximating the minimal nonnegative solution of these equations that relies on semi-infinite quasi-Toeplitz matrix arithmetic. In particular, we show that the algorithm of cyclic reduction can be effectively applied and can approxi- mate the infinite-dimensional solutions with quadratic convergence at a cost that is comparable to that of the finite case. This way, we may compute a finite approximation of the sought solution and of the invariant probability measure of the associated quasi-birth-death process, within a given accuracy. Numerical experiments, performed on a collection of benchmarks, confirm the theoretical analysis.Source: Numerical linear algebra with applications (Online) 25 (2018). doi:10.1002/nla.2128
DOI: 10.1002/nla.2128
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2019 Journal article Open Access

Fast and backward stable computation of the eigenvalues and eigenvectors of matrix polynomials
Aurentz J., Mach T., Robol L., Vandebril R., Watkins D. S.
In the last decade matrix polynomials have been investigated with the primary focus on adequate linearizations and good scaling techniques for computing their eigenvalues and eigenvectors. In this article we propose a new method for computing a factored Schur form of the associated companion pencil. The algorithm has a quadratic cost in the degree of the polynomial and a cubic one in the size of the coefficient matrices. Also the eigenvectors can be computed at the same cost. The algorithm is a variant of Francis's implicitly shifted QR algorithm applied on the companion pencil. A preprocessing unitary equivalence is executed on the matrix polynomial to simultaneously bring the leading matrix coefficient and the constant matrix term to triangular form before forming the companion pencil. The resulting structure allows us to stably factor each matrix of the pencil as a product of k matrices of unitary-plus-rank-one form, admitting cheap and numerically reliable storage. The problem is then solved as a product core chasing eigenvalue problem. A backward error analysis is included, implying normwise backward stability after a proper scaling. Computing the eigenvectors via reordering the Schur form is discussed as well. Numerical experiments illustrate stability and efficiency of the proposed methods.Source: Mathematics of computation (Online) 88 (2019): 313–347. doi:10.1090/mcom/3338
DOI: 10.1090/mcom/3338
DOI: 10.48550/arxiv.1611.10142
Project(s): FUNCOMP via OpenAIRE

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