AMS Acta
(4.910 recursos)
Repository of the University of Bologna.
Mostrando recursos 1 - 20 de 71
1.
Connotative meaning in English and Italian Colour-Word Metaphors - Philip, Gill
Languages are full of colour word expressions which allude to senses that lie well beyond the literal extensions of colour denotation: black humour, purple prose, red letter day; to feel blue, to be in the pink, to see red. The use of these phrases on an everyday basis is seen to add weight to their authority and appropriateness as examples of figurative or symbolic meanings in a wider sense; and their use serves in turn to reinforce the currency of the connotative meanings to which they refer. But what link is there between linguistic expressions and the multitude of symbolic...
2.
On the Optimal Designs for Gaussian Ordinary Kriging with exponential correlation structure - Baldi Antognini, Alessandro; Zagoraiou, Maroussa
The present paper deals with optimal designs for Gaussian random fields with constant trend and exponential correlation structure, widely known as the Ornstein-Uhlenbeck process. Assuming the Maximum Likelihood approach, we study the optimal design problem for the estimation of the trend and the correlation parameter using a criterion based on the Fisher information matrix. When the interest lies in the estimation of the trend, we prove that the equispaced design is optimal for any sample size; while does not exist the optimal design for the estimation of the correlation parameter. Furthermore, the optimal strategies for both parameters conflicts since the...
3.
Testing the performance of image
representations for mass classification in
digital mammograms - Angelini, Enrico; Campanini, Renato; Iampieri, Emiro; Lanconelli, Nico; Masotti, Matteo; Roffilli, Matteo
In this paper a two-class classification problem is faced. One class is constituted
by tumoral masses, breast tumors with size ranging from 3 mm to 30 mm. The
other class is constituted by non-masses. A Support Vector Machine (SVM) is used
as a classifier. Both, masses and non-masses, are extracted from the University
of South Florida (USF) mammographic image database and are presented to the
classifier as crops with pixel size 64 x 64. In order to find the optimal solution to
this problem, different featureless crops representations are evaluated. In particular,
a pixel-based representation, a Discrete Wavelet Transform (DWT) representation
and an Overcomplete Wavelet Transform (OWT) representation...
4.
A ranklet–based image representation for
mass classification in digital mammograms - Masotti, Matteo
Ranklets are non–parametric, multi–resolution and orientation selective features
modelled on Haar wavelets. A ranklet–based image representation is proposed in
this paper in order to solve a two–class classification problem. The first class is
constituted by masses, breast tumors with size ranging from 3 mm to 30 mm,
whereas the second class is constituted by non–masses. Masses and non–masses are
both extracted from the University of South Florida (USF) mammographic image
database, submitted to the ranklet transform and finally classified by means of a
Support Vector Machine (SVM). Experiments demonstrate that the proposed image
representation solves succesfully the two–class classification problem. Furthermore,
it achieves an improvement over the pixel–based and...
5.
Analytic smoothing effect for the Schrodinger equation
with long-range perturbation - Martinez, Andre'; Nakamura, Shu; Sordoni, Vania
We study microlocal analytic singularity of solutions to
Schr\"odinger equation with analytic coefficients.
Using microlocal weight estimate developped for estimating
the phase space tunneling, we prove microlocal smoothing
estimates that generalize results by L. Robbiano and C. Zuily.
We suppose the Schr\"odinger operator is a long-range type perturbation of the Laplacian, and we employ positive commutator
type estimates to prove the smoothing property.
6.
Support vector regression filtering for reduction of false positives in a mass detection cad scheme: preliminary results - Angelini, Enrico; Campanini, Renato; Riccardi, A
Reduction of False Positive signals (FPR) is a fundamental, yet awkward, step in computer aided mass detection schemes.
This paper describes preliminary results of a filtering approach to FPR based on Support Vector Regression (SVR), a machine
learning algorithm arising from a well-founded theoretical framework, the Statistical Learning Theory, which has recently
proved to be superior to the conventional Neural Network framework for both classification and regression tasks: indeed, the
proposed filtering method belongs to the family of neural filters.
The SVR filter is forced to associate subregions extracted from input images, masses and non-masses, to continuous output
values ranging from 0 to 1 representing a...
7.
Calibration of the Hobson&Rogers model: empirical tests - Foschi, P.; Pascucci, A.
The path-dependent volatility model by Hobson and Rogers is considered. It is known that this model can potentially reproduce the observed smile and skew patterns of different directions, while preserving the completeness of the market. In order to quantitatively investigate the pricing performance of the model a calibration procedure is here derived.
Numerical results based on S&P500 option prices give evidence of the effectiveness of the model.
8.
EXPLORING RANKLETS PERFORMANCES IN MAMMOGRAPHIC MASS
CLASSIFICATION USING RECURSIVE FEATURE ELIMINATION - Masotti, Matteo
The ranklet transform is a recent image processing technique
characterized by a multi–resolution and orientation
selective approach similar to that of the wavelet transform.
Yet, differently from the latter, it deals with the ranks of
the pixels rather than with their gray–level intensity values.
In this paper ranklets are used as classification features for a mammographic mass classification problem.
Their performances are explored recursively eliminating some of the less discriminant ranklets coefficients according to the cost function of a Support Vector Machine (SVM) classifier.
Experiments show good classification performances even after
a significant reduction of the number of ranklet coefficients.
9.
Harnack inequality for hypoelliptic ultraparabolic equations with a singular lower order term - Polidoro, Sergio; Ragusa, Maria Alessandra
We prove a Harnack inequality for the positive solutions of ultraparabolic equations of the type
L u + V u= 0,
where L is a linear second order hypoelliptic operator and V
belongs to a class of functions of Stummel-Kato type. We also obtain the existence of a Green function and an uniqueness result for the Cauchy-Dirichlet problem.
10.
Parametrix approximations for option prices - Corielli, Francesco; Pascucci, Andrea
We propose the use of a classical tool in PDE theory, the
parametrix method, to build approximate solutions to generic
parabolic models for pricing and hedging contingent claims. We
obtain an expansion for the price of an option using as starting
point the classical Black&Scholes formula. The approximation can
be truncated to any number of terms and easily computable error
measures are available.
11.
Habeas Corpus: direct access, salience, and delexicalisation in corpus-based metaphor studies - Philip, Gill
In recent years, much has been said about the ways in which figurative language is processed. Two of the principal trends offer apparently irreconcilable views on the subject. On the one hand, the ‘direct-access view’ (Gibbs 2002) argues that the processing of figurative language does not differ significantly from that of non-figurative language. Contrasting with this is the ‘graded salience hypothesis’ (Giora 2002), in which it is argued that the successful interpretation of a language item is determined by its degree of saliency. With regard to these standpoints it must be highlighted that each addresses a different type of figurative...
12.
Identifying Multi-Word Units in Context - Philip, Gill
Abstract: Far from being linguistic anomalies, multi-word expressions abound in natural language, yet their identification is surprisingly problematic. The same combination of words can occur as a compositional, fully lexical string or as a delexicalised multi-word unit (MWU). How can these different manifestations of a series of words be distinguished one from the other? To exacerbate the problem, the creativity of language users results in the appearance of non-canonical forms of MWUs. How can these innovative uses be retrieved so that they can be incorporated into a comprehensive analysis of the MWU under study? This paper sets forth procedures for...
13.
Graphs with prescribed the trace of the Levi form - Martino, Vittorio; Montanari, Annamaria
We prove existence and uniqueness of a viscosity solution of the Dirichlet problem related to the prescribed Levi mean curvature equation, under suitable assumptions on the boundary data and on the Levi curvature of the domain. We also show that such a solution is Lipschitz continuous by proving that it is the uniform limit of a sequence of classical solutions of elliptic problems and by building Lipschitz continuous barriers.
14.
Schauder estimates, Harnack inequality and Gaussian lower bound for Kolmogorov type operators in non-divergence form - Di Francesco, Marco; Polidoro, Sergio
We prove some Schauder type estimates and an invariant Harnack
inequality for a class of degenerate evolution operators of Kolmogorov type. We also prove a Gaussian lower bound for the
fundamental solution of the operator and a uniqueness result for the Cauchy problem. The proof of the lower bound is obtained by solving a suitable optimal control problem and using the invariant Harnack inequality.
15.
A Variable Neighborhood Search for the Capacitated Arc Routing Problem with Intermediate Facilities - Polacek, Michael; Doerner, Karl F.; Hartl, Richard F.; Maniezzo, Vittorio
The capacitated arc routing problem (CARP) focuses on servicing edges of an undirected network graph. A wide spectrum of applications like mail delivery, waste collection or street maintenance outlines the relevance of this problem. A realistic variant of the CARP arises from the need of intermediate facilities (IFs) to load up or unload the service vehicle and from tour length restrictions. The proposed Variable Neighborhood Search (VNS) is a simple and robust solution technique which tackles the basic problem as well as its extensions. Particularly, it outperforms all known heuristics on four sets of benchmark instances.
16.
Experiments with IPv6 multicast at the Academic and Research Network of Lithuania (LITNET)and link to M6Bone - Di Cocco, Luca; Bruzgulis, Vytautas
Multicast saves processing resources at the sender, network bandwidth and enables data to be transferred more
quickly. IPv6 adds a unique and much larger than IP address space, provides security, more efficient routing,
support for mobile and an increased number of multicast addresses. This paper describes a set of tests
accomplished at the IPv6 production network inside the Information Technology Development Institute (ITDI) of
the Kaunas University of Technology (KTU) and the deployment of a test-bed to the purpose to simulate the flow
of multicast packets along the backbone from the upstream provider GEANT2. The link of LITNET to the world-
wide IPv6 multicast test network...
17.
Discriminating mass from normal breast tissue: a novel ranklet image representation for ROI encoding - Masotti, Matteo
A support vector machine (SVM) classifier is used to determine whether regions
of interest (ROIs) found on breast radiographic images contain mass or
normal tissue. Before being presented to SVM, ROIs are encoded by means
of a specific image representation. The coefficients resulting from the encoding
are then used as classification features. Pixel and wavelet image representations
have already been discussed in one of our previous works. A
novel orientation–selective, non–parametric and multi–resolution image representation
is developed and evaluated herein, namely a ranklet image representation.
From the digital database for screening mammography (DDSM)
collected by the University of South Florida, a database of ROIs is generated.
A total of 1000...
18.
Moser type estimates for a class of uniformly subelliptic ultraparabolic operators - Chiara, C.; Polidoro, S.
We consider a class of second order ultraparabolic differential equations with measurable coefficients, that are obtained as a perturbation of hypoelliptic operators.
We assume that the hypoelliptic operators have the form of a sum of squares of vector fields plus a drif term and that the vector fields are invariant with respec to a suitalbe homogeneous Lie group structure.
We adapt the Moser's iterative methods to the non-Euclidean geometry of the Lie groups and we prove a pointwise bound of the solution u in terms of its norm in the L^p space.
19.
k-dimensional Size Functions for shape description and comparison - Biasotti, Silvia; Cerri, Andrea; Giorgi, Daniela
This paper advises the use of k-dimensional size functions for comparison and retrieval in the context of multidimensional shapes, where by shape we mean something in two or higher dimensions having a visual appearance. The attractive feature of k-dimensional size functions is that they allow to readily establish a similarity measure between shapes of arbitrary dimension, taking into account different properties expressed by a multivalued real function defined on the shape. This task is achieved through a particular projection of k-dimensional size functions into the
1-dimensional case. Therefore, previous results on the stability for matching purposes become applicable to a wider...
20.
Keypics: free–hand drawn iconic keywords - Cerri, Andrea; Ferri, Massimo; Frosini, Patrizio; Giorgi, Daniela
We propose an iconic indexing of images to be exposed on the Web. This should be accomplished by “Keypics”, i.e. auxiliary, simplified pictures referring to the geometrical and/or the semantic content of the indexed image. Keypics should not be rigidly standardized; they should be left free to evolve, to express nuances and to stress details. A mathematical tool for dealing with such freedom, in the retrieval task, already exists: Size Functions. An experiment on 494 Keypics with Size Functions based on three measuring functions (distances, projections and jumps) and their combination is presented.
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