28 research outputs found
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
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
Isogeometric analysis-based reduced order modelling for incompressible linear viscous flows in parametrized shapes
No full textIn this work we provide a combination of isogeometric analysis with reduced order modelling techniques, based on proper orthogonal decomposition, to guarantee computational reduction for the numerical model, and with free-form deformation, for versatile geometrical parametrization. We apply it to computational fluid dynamics problems considering a Stokes flow model. The proposed reduced order model combines efficient shape deformation and accurate and stable velocity and pressure approximation for incompressible viscous flows, computed with a reduced order method. Efficient offline–online computational decomposition is guaranteed in view of repetitive calculations for parametric design and optimization problems. Numerical test cases show the efficiency and accuracy of the proposed reduced order model. © 2016 The Author(s)
High-Order Isogeometric Methods for Compressible Flows: I: Scalar Conservation Laws
No full textIsogeometric analysis was applied very successfully to many problem classes like linear elasticity, heat transfer and incompressible flow problems but its application to compressible flows is very rare. However, its ability to accurately represent complex geometries used in industrial applications makes IGA a suitable tool for the analysis of compressible flow problems that require the accurate resolution of boundary layers. The convection-diffusion solver presented in this chapter, is an indispensable step on the way to developing a compressible solver for complex viscous industrial flows. It is well known that the standard Galerkin finite element method and its isogeometric counterpart suffer from spurious oscillatory behaviour in the presence of shocks and steep solution gradients. As a remedy, the algebraic flux correction paradigm is generalized to B-Spline basis functions to suppress the creation of oscillations and occurrence of non-physical values in the solution. This work provides early results for scalar conservation laws and lays the foundation for extending this approach to the compressible Euler equations in the next chapter.Accepted author manuscriptNumerical Analysi
Phase Field-Based Incompressible Two-Component Liquid Flow Simulation
No full textIn this work, we consider a Cahn–Hilliard phase field-based computational model for immiscible and incompressible two-component liquid flows with interfacial phenomena. This diffuse-interface complex-fluid model is given by the incompressible Navier–Stokes–Cahn–Hilliard (NSCH) equations. The coupling of the flow and phase field equations is given by an extra phase induced surface tension force term in the flow equations and a fluid induced transport term in the Cahn–Hilliard (CH) equations. Galerkin-based isogeometric finite element analysis is applied for space discretization of the coupled system in velocity–pressure–phase field–chemical potential formulation. For the approximation of the velocity and pressure fields, LBB compatible non-uniform rational B-spline spaces are used which can be regarded as smooth generalizations of Taylor–Hood pairs of finite element spaces. The one-step θ-scheme is used for the discretization in time. For the validation of the two-phase flow model, we present numerical results for the challenging Rayleigh-Taylor instability flow problem in two dimensions and compare them to reference results.Accepted author manuscriptNumerical Analysi
High-Order Isogeometric Methods for Compressible Flows: II: Compressible Euler Equations
No full textThis work extends the high-resolution isogeometric analysis approach established in chapter “High-Order Isogeometric Methods for Compressible Flows. I: Scalar Conservation Laws” (Jaeschke and Möller: High-order isogeometric methods for compressible flows. I. Scalar conservation Laws. In: Proceedings of the 19th International Conference on Finite Elements in Flow Problems (FEF 2017)) to the equations of gas dynamics. The group finite element formulation is adopted to obtain an efficient assembly procedure for the standard Galerkin approximation, which is stabilized by adding artificial viscosities proportional to the spectral radius of the Roe-averaged flux-Jacobian matrix. Excess stabilization is removed in regions with smooth flow profiles with the aid of algebraic flux correction (Kuzmin et al., Flux-corrected transport, chapter Algebraic flux correction II. Compressible Flow Problems. Springer, Berlin, 2012). The underlying principles are reviewed and it is shown that linearized FCT-type flux limiting (Kuzmin, J Comput Phys 228(7):2517–2534, 2009) originally derived for nodal low-order finite elements ensures positivity-preservation for high-order B-Spline discretizations.Accepted author manuscriptNumerical Analysi
Optimization Based Particle-Mesh Algorithm for High-Order and Conservative Scalar Transport
No full textA particle-mesh strategy is presented for scalar transport problems which provides diffusion-free advection, conserves mass locally (i.e. cellwise) and exhibits optimal convergence on arbitrary polyhedral meshes. This is achieved by expressing the convective field naturally located on the Lagrangian particles as a mesh quantity by formulating a dedicated particle-mesh projection based via a PDE-constrained optimization problem. Optimal convergence and local conservation are demonstrated for a benchmark test, and the application of the scheme to mass conservative density tracking is illustrated for the Rayleigh–Taylor instability.Accepted Author ManuscriptRivers, Ports, Waterways and Dredging EngineeringEnvironmental Fluid Mechanic
Advances in geometrical parametrization and reduced order models and methods for computational fluid dynamics problems in applied sciences and engineering: overview and perspectives
No full textSeveral problems in applied sciences and engineering require reduction techniques in order to allow computational tools to be employed in the daily practice, especially in iterative procedures such as optimization or sensitivity analysis. Reduced order methods need to face increasingly complex problems in computational mechanics, especially into a multiphysics setting. Several issues should be faced: stability of the approximation, efficient treatment of nonlinearities, uniqueness or possible bifurcations of the state solutions, proper coupling between fields, as well as offline-online computing, computational savings and certification of errors as measure of accuracy. Moreover, efficient geometrical parametrization techniques should be devised to efficiently face shape optimization problems, as well as shape reconstruction and shape assimilation problems. A related aspect deals with the management of parametrized interfaces in multiphysics problems, such as fluid-structure interaction problems, and also a domain decomposition based approach for complex parametrized networks. We present some illustrative
industrial and biomedical problems as examples of recent advances on methodological developments. © The author
Real-time reduced basis techniques for Navier-Stokes equations: Optimization of parametrized bypass configurations
No full textThe reduced basis method on parametrized domains is applied to approximate blood flow through an arterial bypass. The aim is to provide (a) a sensitivity analysis for relevant geometrical quantities of interest in bypass configurations and (b) rapid and reliable prediction of integral functional outputs ( such as fluid mechanics indexes). The goal of this investigation is (i) to achieve design indications for arterial surgery in the perspective of future development for prosthetic bypasses, (ii) to develop numerical methods for optimization and design in biomechanics, and (iii) to provide an input-output relationship led by models with lower complexity and computational costs than the complete solution of fluid dynamics equations by a classical finite element method
