458 research outputs found
Efficient geometrical parametrisation techniques of interfaces for reduced-order modelling: application to fluid-structure interaction coupling problems
No full textWe present some recent advances and improvements in shape parametrisation techniques of interfaces for reduced-order modelling with special attention to fluid–structure interaction problems and the management of structural deformations, namely, to represent them into a low-dimensional space (by control points). This allows to reduce the computational effort, and to significantly simplify the (geometrical) deformation procedure, leading to more efficient and fast reduced-order modelling applications in this kind of problems. We propose an efficient methodology to select the geometrical control points for the radial basis functions based on a modal greedy algorithm to improve the computational efficiency in view of more complex fluid–structure applications in several fields. The examples provided deal with aeronautics and wind engineering. © 2014, © 2014 Taylor & Francis
Il 'De talento' di Porcelio de' Pandoni e le sue fonti
No full textPorcelio de’ Pandoni composed the Opusculum aureum de talento for his friend Cicco Simonetta,
the Secretary of Francesco Sforza. The work is dated February 1st, 1459, therefore represents
the first pamphlet on numismatics to be realized in xv century. Although the De talento was
composed in Milan, his author was certainly influenced by the Neapolitan Kingdom’s cultural
environment, especially by Alfonso the Magnanimous, who was a great ancient coin collector
and enjoyed the presence of specialists in the creation of medals. In this paper, is also examined
the framework of the De talento, with a particular focus on its literary sources
Un ponte sul Mediterraneo: Leonardo Fibonacci e i percorsi delle scienze matematiche nel Medioevo
No full textIl seminario si concentra sulle sfide ecdotiche insite nell'edizione critica di un'opera affascinante e complessa, quale appunto il Liber abaci d Leonardo Pisano, detto il Fibonacc
Alcune considerazioni sui 'Varia poemata' di Giano Anisio (1531)
No full textSommario · La silloge dei Varia poemata di Giano Anisio è un’opera di straordinaria complessità, sia per la
ricchezza dei temi trattati e dei generi letterari ivi rappresentati, sia per la presenza di un elevato numero
di dedicatari, alcuni dei quali non sono facilmente identificabili. L’opera ebbe una genesi editoriale assai
turbolenta: durante l’assedio di Napoli del 1528, infatti, l’autore perse il manoscritto originariamente
destinato alla stampa e fu costretto ad allestire un nuovo codice in tutta fretta, servendosi degli appunti
che aveva a disposizione e facendo per lo più affidamento sulla sua memoria. La raccolta, che appare
ancorata ad un rigoroso classicismo militante, si ispira ai due criteri fondamentali della varietas e della
citazione allusiva, che risulta talvolta oscura. Meno definito appare, invece, il criterio della consequenzialità cronologica della disposizione dei carmi, un principio che l’autore afferma all’inizio dell’opera, ma
che di fatto non appare pienamente applicato all’interno della raccolta.
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Abstract · Some considerations on Giano Anisio’s Varia poemata (1531) · Giano Anisio’s Varia poemata is
a work of extraordinary complexity, both for the richness of the topics and the literary genres here
represented and for the presence of a large number of dedicatees, some of which are not easily identifiable. The work had a very turbulent editorial genesis: during the siege of Naples in 1528, in fact, the
author lost the manuscript originally intended for printing and was forced to prepare a new codex in a
hurry, using the notes at his disposal and mainly relying on his memory. The collection, which appears
anchored to a rigorous militant classicism, is inspired by the two fundamental criteria of variety and
allusive quotation, which is sometimes obscure. The criterion of the chronological consequentiality of
the arrangement of the poems, a principle that the author affirms at the beginning of the work, does not
appear fully applied within the collection
Fibonacci’s Pratica geometrie: philological and linguistic remarks on Distinctio VII.
No full textThe paper analyses the seventh distinction of Fibonacci's Pratica Geometrie, dedicated to the heights, and examines its manuscripts' tradition. The calculations are performed using specific measuring instruments, as well as by applying classical geometric theorems. Leonard first explains how to use a vertical stuff of known height (asta in Latin) to determine the height of an object situated at a certain distance by employing the theory of proportions. The author then shows a simple method for calculating the heights of masts suitable for shipbuilding. He recommends using a vertical rod (arundo) as tall as the measurer (mensor). The mensor then lies down on the ground with his feet towards the rod and proceeds as in the previous examples. A third method involves the application of the Pythagorean theorem, as described by Euclid in the first book of the Elements. Leonard presents an exemplum fictum, a fake strategy, in which the mensor uses a bow (arcus) and two arrows (sagittae). He ties two strings of known length to the arrows and then shoots them at the height he wishes to measure, one upwards and the other downwards. The choice of using bow and arrows is rather peculiar, but it is also an example of Leonard’s creativity, as he often devises imaginative exercises in his works. Finally, the author introduces and explains how to use two tools for calculating heights using the properties of similar triangles. One of these tools is the so-called wooden triangle, an instrument frequently used by architects; the second is the well-known quadrant, also called oroscopum. As Annalisa Simi explains, the quadrant is made up of two rigid rods of equal length that define a 90-degree circular sector. A string with a small weight (plumbinum) is attached to the vertex, and two holes are drilled along one of the straight sides. By holding the quadrant vertically and aligning the holes with the upper part of the object we want to measure, the elevation angle can be read from the graduated scale based on the position of the plumbinum
A combination between the reduced basis method and the ANOVA expansion: On the computation of sensitivity indices
No full textWe consider a method to efficiently evaluate in a real-time context an output based on the numerical solution of a partial differential equation depending on a large number of parameters. We state a result allowing to improve the computational performance of a three-step RB-ANOVA-RB method. This is a combination of the reduced basis (RB) method and the analysis of variations (ANOVA) expansion, aiming at compressing the parameter space without affecting the accuracy of the output. The idea of this method is to compute a first (coarse) RB approximation of the output of interest involving all the parameter components, but with a large tolerance on the a posteriori error estimate; then, we evaluate the ANOVA expansion of the output and freeze the least important parameter components; finally, considering a restricted model involving just the retained parameter components, we compute a second (fine) RB approximation with a smaller tolerance on the a posteriori error estimate. The fine RB approximation entails lower computational costs than the coarse one, because of the reduction of parameter dimensionality. Our result provides a criterion to avoid the computation of those terms in the ANOVA expansion that are related to the interaction between parameters in the bilinear form, thus making the RB-ANOVA-RB procedure computationally more feasible. © 2013 Académie des sciences
Chapter 12: Weighted Reduced Order Methods for Uncertainty Quantification
No full textPartial differential equations (PDEs) represent an effective tool to model phenomena in applied
sciences. Realistic problems usually depend on several physical and geometrical parameters that
can be calibrated exploiting real data. In real scenarios, however, these parameters are affected
by uncertainty due to measurement errors or scattered data information. To deal with more reli-
able models which take into account this issue, the numerical approximation of stochastic PDEs
can be exploited. In the Uncertainty Quantification (UQ) context, many simulations are run to
better understand the system at hand and to compute statistics of outcomes over quantities of
interest. In particular, the input parameters of the stochastic PDEs are assumed to be random
finite–dimensional variables
An optimisation–based domain–decomposition reduced order model for the incompressible Navier-Stokes equations
No full textThe aim of this work is to present a model reduction technique in the framework of optimal control problems for partial differential equations. We combine two approaches used for reducing the computational cost of the mathematical numerical models: domain–decomposition (DD) methods and reduced–order modelling (ROM). In particular, we consider an optimisation–based domain–decomposition algorithm for the parameter–dependent stationary incompressible Navier–Stokes equations. Firstly, the problem is described on the subdomains coupled at the interface and solved through an optimal control problem, which leads to the complete separation of the subdomain problems in the DD method. On top of that, a reduced model for the obtained optimal–control problem is built; the procedure is based on the Proper Orthogonal Decomposition technique and a further Galerkin projection. The presented methodology is tested on two fluid dynamics benchmarks: the stationary backward–facing step and lid-driven cavity flow. The numerical tests show a significant reduction of the computational costs in terms of both the problem dimensions and the number of optimisation iterations in the domain–decomposition algorithm
Short (8-mm) dental implants in the rehabilitation of partial and complete edentulism : a 3- to 14-year longitudinal study
No full textPURPOSE: This study aimed to evaluate the clinical effectiveness of different implant sizes (8- and 10-mm lengths with 3.75-, 4.1-, and 4.8-mm diameters) in diverse host bone sites in a selected sample of partially and completely edentulous patients. MATERIALS AND METHODS: Over a 14-year period, 129 patients (68 women and 61 men) were consecutively treated with a fixed prosthesis (single or multiunit, screw or cement retained) supported by 265 different-sized implants (154 standard 10-mm; 111 shorter 8-mm). Two types of implants were used (141 titanium plasma-sprayed and 124 Sand-blasted, large-grit, acid-etched). RESULTS: Dropouts were recorded for 23 patients with 23 prostheses supported by 42 implants. In the remaining 106 patients (223 implants), 8 implants failed (4 standard and 4 shorter), in type 3 or 4 bone. Mean marginal bone loss and gingival crevice probing depth associated with either implant length were statistically comparable (P> .05). The 14-year cumulative survival rates for all short and standard implants were 97.9% and 97.1%, respectively. Survival rates were 92.3% and 95.9% for titanium plasma-sprayed short and standard implants, respectively, and 100% and 98.5% for the Sand-blasted, large-grit, acid-etched short and standard implants, respectively. Six of the 8 lost implants required implant replacement after the host sites' healing period. The remaining 2 lost implants were managed by converting the distal unit of the fixed partial prosthesis to a cantilever. CONCLUSION: Within the limits of the study design and observation period, a mix of implant sizes did not appear to compromise the effectiveness of implant therapy in this particular population group
Modeling of Physiological Flows
No full textThis book offers a mathematical update of the state of the art of the research in the field of mathematical and numerical models of the circulatory system. It is structured into different chapters, written by outstanding experts in the field. Many fundamental issues are considered, such as: the mathematical representation of vascular geometries extracted from medical images, modelling blood rheology and the complex multilayer structure of the vascular tissue, and its possible pathologies, the mechanical and chemical interaction between blood and vascular walls, and the different scales coupling local and systemic dynamics. All of these topics introduce challenging mathematical and numerical problems, demanding for advanced analysis and efficient simulation techniques, and pay constant attention to applications of relevant clinical interest. This book is addressed to graduate students and researchers in the field of bioengineering, applied mathematics and medicine, wishing to engage themselves in the fascinating task of modeling the cardiovascular system or, more broadly, physiological flows
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