126 research outputs found
A Novel Graph-Based Fisher Kernel Method for Semi-supervised Learning
No full textGraph-based semi-supervised learning methods play a key role in machine learning applications, particularly when no parametric information or other prior knowledge is available. Given a graph whose nodes represent the points and the weighted edges the relations between them, the goal is to predict the values of all unlabeled nodes exploiting the information provided by both label and unlabeled nodes. In this paper, we propose a novel graph-based approach for semi-supervised binary classification. The algorithm extends the Fisher Subspace estimation approaches by adopting a kernel graph covariance measure. This similarity measure defines a relation between nodes generalizing both the shortest path and the commute time distance. This quantity is called the sum-over-paths covariance. Experiments on synthetic and real-world datasets highlight that the proposed algorithm achieves better results with respect to those obtained by state-of-the-art compet
A POD-selective inverse distance weighting method for fast parametrized shape morphing
No full textEfficient shape morphing techniques play a crucial role in the approximation of partial differential equations defined in parametrized domains, such as for fluid-structure interaction or shape optimization problems. In this paper, we focus on inverse distance weighting (IDW) interpolation techniques, where a reference domain is morphed into a deformed one via the displacement of a set of control points. We aim at reducing the computational burden characterizing a standard IDW approach without significantly compromising the accuracy. To this aim, first we propose an improvement of IDW based on a geometric criterion that automatically selects a subset of the original set of control points. Then, we combine this new approach with a dimensionality reduction technique based on a proper orthogonal decomposition of the set of admissible displacements. This choice further reduces computational costs. We verify the performances of the new IDW techniques on several tests by investigating the trade-off reached in terms of accuracy and efficiency
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
The Effort of Increasing Reynolds Number in Projection-Based Reduced Order Methods: From Laminar to Turbulent Flows
No full textWe present in this double contribution two different reduced order strategies for incompressible parameterized Navier-Stokes equations characterized by varying Reynolds numbers. The first strategy deals with low Reynolds number (laminar flow) and is based on a stabilized finite element method during the offline stage followed by a Galerkin projection on reduced basis spaces generated by a greedy algorithm. The second methodology is based on a full order finite volume discretization. The latter methodology will be used for flows with moderate to high Reynolds number characterized by turbulent patterns. For the treatment of the mentioned turbulent flows at the reduced order level, a new POD-Galerkin approach is proposed. The new approach takes into consideration the contribution of the eddy viscosity also during the online stage and is based on the use of interpolation. The two methodologies are tested on classic benchmark test cases
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
Measuring Brand-Influencer Visual Congruence on Instagram Using Deep Learning and Automated Image Recognition
No full textTruncated Isotropic Principal Component Classifier for Image Classification
No full textThis paper reports a novel approach to deal with the problem of Object and Scene recognition extending the traditional Bag of Words approach in two ways. Firstly, a dataset independent method of summarizing local features, based on multivariate Gaussian descriptors, is employed. Secondly, a recently proposed classification technique, particularly suited for high dimensional feature spaces without any dimensionality reduction step, allows to effectively exploit these features. Experiments are performed on two publicly available datasets and demonstrate the effectiveness of our approach when compared to state-of-the-art methods
Data-driven discovery of delay differential equations with discrete delays
No full textThe Sparse Identification of Nonlinear Dynamics (SINDy) framework is a robust method for identifying governing equations, successfully applied to ordinary, partial, and stochastic differential equations. In this work we extend SINDy to identify delay differential equations by using an augmented library that includes delayed samples and Bayesian optimization. To identify a possibly unknown delay we minimize the reconstruction error over a set of candidates. The resulting methodology improves the overall performance by remarkably reducing the number of calls to SINDy with respect to a brute force approach. We also address a multivariate setting to identify multiple unknown delays and (non-multiplicative) parameters. Several numerical tests on delay differential equations with different long-term behavior, number of variables, delays, and parameters support the use of Bayesian optimization highlighting both the efficacy of the proposed methodology and its computational advantages. As a consequence, the class of discoverable models is significantly expanded
Performance comparision of secure and insecure VoIP environments
No full textThis paper deals with techniques of measuring and assessment of the voice transmitted in IP networks in secure and insecure environment using different virtual testbeds and a real implementation based on OpenSer. They realised their real platform, in order to understand how the voice services in IP network are affected by using the secure IP environment. The real performance test was implemented between VSB-Technical University in Ostrava and University degli studi of Milan
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