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Showing papers by "University of Trento published in 2005"


Journal ArticleDOI
TL;DR: This paper assesses performance of regularized radial basis function neural networks (Reg-RBFNN), standard support vector machines (SVMs), kernel Fisher discriminant (KFD) analysis, and regularized AdaBoost (reg-AB) in the context of hyperspectral image classification.
Abstract: This paper presents the framework of kernel-based methods in the context of hyperspectral image classification, illustrating from a general viewpoint the main characteristics of different kernel-based approaches and analyzing their properties in the hyperspectral domain. In particular, we assess performance of regularized radial basis function neural networks (Reg-RBFNN), standard support vector machines (SVMs), kernel Fisher discriminant (KFD) analysis, and regularized AdaBoost (Reg-AB). The novelty of this work consists in: 1) introducing Reg-RBFNN and Reg-AB for hyperspectral image classification; 2) comparing kernel-based methods by taking into account the peculiarities of hyperspectral images; and 3) clarifying their theoretical relationships. To these purposes, we focus on the accuracy of methods when working in noisy environments, high input dimension, and limited training sets. In addition, some other important issues are discussed, such as the sparsity of the solutions, the computational burden, and the capability of the methods to provide outputs that can be directly interpreted as probabilities.

1,428 citations


Book ChapterDOI
TL;DR: This paper presents a new classification of schema-based matching techniques that builds on the top of state of the art in both schema and ontology matching and distinguishes between approximate and exact techniques at schema-level; and syntactic, semantic, and external techniques at element- and structure-level.
Abstract: Schema and ontology matching is a critical problem in many application domains, such as semantic web, schema/ontology integration, data warehouses, e-commerce, etc. Many different matching solutions have been proposed so far. In this paper we present a new classification of schema-based matching techniques that builds on the top of state of the art in both schema and ontology matching. Some innovations are in introducing new criteria which are based on (i) general properties of matching techniques, (ii) interpretation of input information, and (iii) the kind of input information. In particular, we distinguish between approximate and exact techniques at schema-level; and syntactic, semantic, and external techniques at element- and structure-level. Based on the classification proposed we overview some of the recent schema/ontology matching systems pointing which part of the solution space they cover. The proposed classification provides a common conceptual basis, and, hence, can be used for comparing different existing schema/ontology matching techniques and systems as well as for designing new ones, taking advantages of state of the art solutions.

1,285 citations


Journal ArticleDOI
TL;DR: Experimental evaluation confirms that MaltParser can achieve robust, efficient and accurate parsing for a wide range of languages without language-specific enhancements and with rather limited amounts of training data.
Abstract: Parsing unrestricted text is useful for many language technology applications but requires parsing methods that are both robust and efficient. MaltParser is a language-independent system for data-driven dependency parsing that can be used to induce a parser for a new language from a treebank sample in a simple yet flexible manner. Experimental evaluation confirms that MaltParser can achieve robust, efficient and accurate parsing for a wide range of languages without language-specific enhancements and with rather limited amounts of training data.

801 citations


Journal ArticleDOI
TL;DR: Experiments carried out on two sets of multitemporal images acquired by the European Remote Sensing 2 satellite SAR sensor confirm the effectiveness of the proposed unsupervised approach, which results in change-detection accuracies very similar to those that can be achieved by a manual supervised thresholding.
Abstract: We present a novel automatic and unsupervised change-detection approach specifically oriented to the analysis of multitemporal single-channel single-polarization synthetic aperture radar (SAR) images. This approach is based on a closed-loop process made up of three main steps: (1) a novel preprocessing based on a controlled adaptive iterative filtering; (2) a comparison between multitemporal images carried out according to a standard log-ratio operator; and (3) a novel approach to the automatic analysis of the log-ratio image for generating the change-detection map. The first step aims at reducing the speckle noise in a controlled way in order to maximize the discrimination capability between changed and unchanged classes. In the second step, the two filtered multitemporal images are compared to generate a log-ratio image that contains explicit information on changed areas. The third step produces the change-detection map according to a thresholding procedure based on a reformulation of the Kittler-Illingworth (KI) threshold selection criterion. In particular, the modified KI criterion is derived under the generalized Gaussian assumption for modeling the distributions of changed and unchanged classes. This parametric model was chosen because it is capable of better fitting the conditional densities of classes in the log-ratio image. In order to control the filtering step and, accordingly, the effects of the filtering process on change-detection accuracy, we propose to identify automatically the optimal number of despeckling filter iterations [Step 1] by analyzing the behavior of the modified KI criterion. This results in a completely automatic and self-consistent change-detection approach that avoids the use of empirical methods for the selection of the best number of filtering iterations. Experiments carried out on two sets of multitemporal images (characterized by different levels of speckle noise) acquired by the European Remote Sensing 2 satellite SAR sensor confirm the effectiveness of the proposed unsupervised approach, which results in change-detection accuracies very similar to those that can be achieved by a manual supervised thresholding.

688 citations


Journal ArticleDOI
TL;DR: Techniques and algorithms developed in the framework of Statistical Learning Theory are applied to the problem of determining the location of a wireless device by measuring the signal strength values from a set of access points (location fingerprinting), with the advantage of a low algorithmic complexity in the normal operating phase.

602 citations


Journal ArticleDOI
TL;DR: In this article, a planar microcavity photon mode strongly coupled to a semiconductor inter-subband transition in presence of a two-dimensional electron gas is described. And the quantum properties of the ground state (a two-mode squeezed vacuum), which can be tuned in situ by changing the value of the Rabi frequency, e.g., through an electrostatic gate.
Abstract: We present a quantum description of a planar microcavity photon mode strongly coupled to a semiconductor intersubband transition in presence of a two-dimensional electron gas. We show that, in this kind of system, the vacuum Rabi frequency ${\ensuremath{\Omega}}_{R}$ can be a significant fraction of the intersubband transition frequency ${\ensuremath{\omega}}_{12}$. This regime of ultrastrong light-matter coupling is enhanced for long-wavelength transitions, because for a given doping density, effective mass and number of quantum wells, the ratio ${\ensuremath{\Omega}}_{R}∕{\ensuremath{\omega}}_{12}$ increases as the square root of the intersubband emission wavelength. We characterize the quantum properties of the ground state (a two-mode squeezed vacuum), which can be tuned in situ by changing the value of ${\ensuremath{\Omega}}_{R}$, e.g., through an electrostatic gate. We finally point out how the tunability of the polariton quantum vacuum can be exploited to generate correlated photon pairs out of the vacuum via quantum electrodynamics phenomena reminiscent of the dynamical Casimir effect.

561 citations


Journal ArticleDOI
TL;DR: In this article, the semi-classical methods for computing the conditions for Hawking radiation as tunneling are revisited and applied also to rotating black hole solutions as well as to the extremal cases.
Abstract: The issue concerning semi-classical methods recently developed in deriving the conditions for Hawking radiation as tunneling, is revisited and applied also to rotating black hole solutions as well as to the extremal cases. It is noticed how the tunneling method fixes the temperature of extremal black hole to be zero, unlike the euclidean regularity method that allows an arbitrary compactification period. A comparison with other approaches is presented.

453 citations


Journal ArticleDOI
TL;DR: In this paper, the semi-classical methods for computing the conditions for Hawking radiation as tunneling are revisited and applied also to rotating black hole solutions as well as to the extremal cases.
Abstract: The issue concerning semi-classical methods recently developed in deriving the conditions for Hawking radiation as tunneling, is revisited and applied also to rotating black hole solutions as well as to the extremal cases. It is noticed how the tunneling method fixes the temperature of extremal black hole to be zero, unlike the Euclidean regularity method that allows an arbitrary compactification period. A comparison with other approaches is presented.

398 citations


Journal ArticleDOI
TL;DR: Experimental results obtained on multitem temporal SAR images acquired by the ERS-1 satellite confirm the effectiveness of the proposed approach to change detection in multitemporal synthetic aperture radar images.
Abstract: This paper presents a novel approach to change detection in multitemporal synthetic aperture radar (SAR) images. The proposed approach exploits a wavelet-based multiscale decomposition of the log-ratio image (obtained by a comparison of the original multitemporal data) aimed at achieving different scales (levels) of representation of the change signal. Each scale is characterized by a different tradeoff between speckle reduction and preservation of geometrical details. For each pixel, a subset of reliable scales is identified on the basis of a local statistic measure applied to scale-dependent log-ratio images. The final change-detection result is obtained according to an adaptive scale-driven fusion algorithm. Experimental results obtained on multitemporal SAR images acquired by the ERS-1 satellite confirm the effectiveness of the proposed approach.

384 citations


Journal ArticleDOI
TL;DR: An optical speckle potential is used to investigate the static and dynamic properties of a Bose-Einstein condensate in the presence of disorder and stripes are observed in the expanded density profile and strong damping of dipole and quadrupole oscillations is seen.
Abstract: An optical speckle potential is used to investigate the static and dynamic properties of a Bose-Einstein condensate in the presence of disorder. With small levels of disorder, stripes are observed in the expanded density profile and strong damping of dipole and quadrupole oscillations is seen. Uncorrelated frequency shifts of the two modes are measured and are explained using a sum-rules approach and by the numerical solution of the Gross-Pitaevskii equation.

343 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present an excerpt of the document "Quantum Information Processing and Communication: Strategic report on current status, visions and goals for research in Europe", which has been recently published in electronic form at the website of FET (the Future and Emerging Technologies Unit of the Directorate General Information Society of the European Commission).
Abstract: We present an excerpt of the document "Quantum Information Processing and Communication: Strategic report on current status, visions and goals for research in Europe", which has been recently published in electronic form at the website of FET (the Future and Emerging Technologies Unit of the Directorate General Information Society of the European Commission, http://www.cordis.lu/ist/fet/qipc-sr.htm). This document has been elaborated, following a former suggestion by FET, by a committee of QIPC scientists to provide input towards the European Commission for the preparation of the Seventh Framework Program. Besides being a document addressed to policy makers and funding agencies (both at the European and national level), the document contains a detailed scientific assessment of the state-of-the-art, main research goals, challenges, strengths, weaknesses, visions and perspectives of all the most relevant QIPC sub-fields, that we report here.

Journal ArticleDOI
TL;DR: Compared to the state-of-art finite-volume WENO schemes the ADER schemes are faster, more accurate, need less computer memory and have no theoretical accuracy barrier.

Journal ArticleDOI
TL;DR: The data show that in a subpopulation of PVS patients with preserved thalamocortical feedback connections, remaining cortical information processing is a consistent finding and may even involve semantic levels of processing.

Proceedings Article
05 Jun 2005
TL;DR: A novel planning framework for the automated composition of web services that are specified and implemented in industrial standard languages for business processes modeling and execution, like BPEL4WS, based on state of the art techniques for planning under uncertainty.
Abstract: We propose a novel planning framework for the automated composition of web services We consider services that are specified and implemented in industrial standard languages for business processes modeling and execution, like BPEL4WS These languages describe web services whose behavior is intrinsically asynchronous For this reason, the key aspect of our framework is the modeling of asynchronous planning problems In the paper we describe the framework and propose a planning approach that is based on state of the art techniques for planning under uncertainty Our experiments show that this approach can scale up to significant cases, ie, to cases in which the manual development of BPEL4WS composed services is not trivial and is time consuming

Journal ArticleDOI
TL;DR: In vitro and in vivo behaviour of an injectable silk fibroin (SF) hydrogel was studied through osteoblast cultures and after implantation in critical-size defects of rabbit distal femurs, confirming that SF hydrogels accelerated remodelling processes.

Journal ArticleDOI
TL;DR: In this article, the authors discuss a scaling approach to business fluctuations and show that a simple financial fragility agent-based model, based on complex interactions of heterogeneous agents, is able to replicate a large number of scaling type stylized facts with a remarkable high degree of statistical precision.
Abstract: In this paper, we discuss a scaling approach to business fluctuations. Our starting point consists in recognizing that concepts and methods derived from physics have allowed economists to (re)discover a set of stylized facts which have to be satisfactorily accounted for in their models. Standard macroeconomics, based on a reductionist approach centered on the representative agent, is definitely badly equipped for this task. On the contrary, we show that a simple financial fragility agent-based model, based on complex interactions of heterogeneous agents, is able to replicate a large number of scaling type stylized facts with a remarkable high degree of statistical precision.

Proceedings Article
30 Jul 2005
TL;DR: This paper starts from descriptions of web services in standard process modeling and execution languages and automatically translates them into a planning domain that models the interactions among services at the knowledge level, to avoid the explosion of the search space due to the usually large and possibly infinite ranges of data values that are exchanged among services.
Abstract: In this paper, we address the problem of the automated composition of web services by planning on their "knowledge level" models. We start from descriptions of web services in standard process modeling and execution languages, like BPEL4WS, and automatically translate them into a planning domain that models the interactions among services at the knowledge level. This allows us to avoid the explosion of the search space due to the usually large and possibly infinite ranges of data values that are exchanged among services, and thus to scale up the applicability of state-of-the-art techniques for the automated composition of web services. We present the theoretical framework, implement it, and provide an experimental evaluation that shows the practical advantage of our approach w.r.t. techniques that are not based on a knowledgelevel representation.

Journal ArticleDOI
TL;DR: This paper adopts a formal goal model defined and analyzed in (J.Tropos), to make the goal analysis process concrete through the use of forward and backward reasoning for goal models.

Proceedings ArticleDOI
29 Aug 2005
TL;DR: This paper refine Secure Tropos, introducing the notions of at-least delegation and trust of execution; also, at-most delegation andTrust of permission; and proposes monitoring as a security design pattern intended to overcome the problem of lack of trust between actors.
Abstract: Security requirements engineering is emerging as a branch of software engineering, spurred by the realization that security must be dealt with early on during the requirements phase. Methodologies in this field are challenging, as they must take into account subtle notions such as trust (or lack thereof), delegation, and permission; they must also model entire organizations and not only systems-to-be. In our previous work we introduced Secure Tropos, a formal framework for modeling and analyzing security requirements. Secure Tropos is founded on three main notions: ownership, trust, and delegation. In this paper, we refine Secure Tropos introducing the notions of at-least delegation and trust of execution; also, at-most delegation and trust of permission. We also propose monitoring as a security design pattern intended to overcome the problem of lack of trust between actors. The paper presents a semantic for these notions, and describes an implemented formal reasoning tool based on Datalog.

Journal ArticleDOI
12 Dec 2005-Polymer
TL;DR: In this paper, a trend inversion in the physical properties was detected at the highest filler level tested, which was not previously observed for epoxy systems filled with comparable amounts of unmodified silica.

Proceedings ArticleDOI
04 Nov 2005
TL;DR: This paper proposes a goal-oriented approach to requirement analysis for data warehouses, based on the Tropos methodology, which can be employed within both a demand-driven and a mixed supply/demand-driven design framework.
Abstract: Several surveys indicate that a significant percentage of data warehouses fail to meet business objectives or are outright failures. One of the reasons for this is that requirement analysis is typically overlooked in real projects. In this paper we propose a goal-oriented approach to requirement analysis for data warehouses, based on the Tropos methodology. Two different perspectives are integrated for requirement analysis: organizational modeling, centered on stakeholders, and decisional modeling, focused on decision makers. Our approach can be employed within both a demand-driven and a mixed supply/demand-driven design framework: in the second case, while the operational sources are still explored to shape hierarchies, user requirements play a fundamental role in restricting the area of interest for analysis and in choosing facts, dimensions, and measures. The methodology proposed, supported by a prototype, is described with reference to a real case study.

Journal ArticleDOI
TL;DR: In this article, an experimental study was carried out to investigate the shear strength of a compacted non-active clay (Speswhite kaolin) and a shearbox was modified to allow the direct measurement of negative pore water pressure using Trento high-suction tensiometers.
Abstract: An experimental study was carried out to investigate the shear strength of a compacted non-active clay (Speswhite kaolin). A total of 33 statically compacted specimens were prepared, at vertical stresses of 300, 600 and 1200 kPa and water contents ranging from 0·24 to 0·34. This made it possible to explore a broad range of initial compaction-induced conditions and hence to examine whether differences in water retention characteristics and shear strength are due to differences in initial compaction-induced state or are to be attributed to fundamentally different microfabrics. A shearbox was modified to allow the direct measurement of negative pore water pressure using Trento high-suction tensiometers. Tests were carried out at constant water content by monitoring suction changes. In these tests, it was possible to investigate the transition from unsaturated to saturated states. In the first stage of the test, the specimen was compressed at constant water content. The specimen was therefore wetted, in the s...

Journal ArticleDOI
TL;DR: In this paper, a four-month ethnography conducted in a hospital that has recently introduced a digital clinical records system is described, and the methodological aspects of this study are discussed.
Abstract: Recent years have seen growing sociological interest in the role that objects and non-human actors perform in everyday life. Whether as machines, information technologies, artworks, commodities or architectures, objects today raise issues of complexity and controversy (Pels et al., 2002). Borrowing from actor network theory the idea that humans and non-humans are actively involved in the making of social worlds, there are already those who call for a post-social world and an object-centred sociality (Knorr-Cetina, 1997). But how can non-humans be observed? Sociologists are accustomed to socio-constructionist approaches to the sociology of science, or to analyses of tools and innovations couched in terms of networks of actants; methodologically, however, it seems that ideas about how to proceed methodologically are not very well worked out. On the basis of a four-month ethnography conducted in a hospital that has recently introduced a digital clinical records system, I discuss the methodological aspects of...

Journal ArticleDOI
TL;DR: In this article, the rheological behavior of high-concentration granular-liquid mixtures is studied using a recirculating flume, where the granular motions are observed through the channel sidewall, and analyzed with recently developed Voronoi imaging methods.
Abstract: Laboratory experiments are conducted to study the rheological behaviour of high-concentration granular-liquid mixtures. Steady uniform free-surface flows are obtained using a recirculating flume. Cases in which a loose deposit forms underneath the flow are contrasted with runs for which basal shear occurs along the flume bottom. The granular motions are observed through the channel sidewall, and analysed with recently developed Voronoi imaging methods. Depth profiles of mean velocity, solid concentration, and granular temperature are obtained, and complemented by stress estimates based on force balance considerations. These measurements are used to probe variations in rheological behaviour over depth, and to clarify the role of the granular temperature. The flows are found to evolve a stratified structure. Distinct sublayers are characterized by either frictional or collisional behaviour, and transitions between one and the other occur at values of the Stokes number which suggest that viscous effects intervene. The observed frictional behaviour is consistent with shear cell tests conducted at very low shear rates. On the other hand, the collisional data corroborate both the Bagnold description and the more recent kinetic theories of granular flows, provided that one accounts for the inertia of the interstitial liquid.

Book ChapterDOI
29 May 2005
TL;DR: The paper describes the design and implementation principles of a distributed reasoning system, called DRAGO (Distributed Reasoning Architecture for a Galaxy of Ontologies), that implements such distributed decision procedure.
Abstract: The paper addresses the problem of reasoning with multiple ontologies interconnected by semantic mappings. This problem is becoming more and more relevant due to the necessity of building the interoperable Semantic Web. In contrast to the so called global reasoning approach, in this paper we propose a distributed reasoning technique that accomplishes reasoning through a combination of local reasoning chunks, internally executed in each separate ontology. Using Distributed Description Logics as a formal framework for representation of multiple semantically connected ontologies, we define a sound and complete distributed tableau-based reasoning procedure which is built as an extension to standard Description Logic tableau. Finally, the paper describes the design and implementation principles of a distributed reasoning system, called DRAGO (Distributed Reasoning Architecture for a Galaxy of Ontologies), that implements such distributed decision procedure.

Journal ArticleDOI
TL;DR: A simulation study indicates that the test involving the proposed entropy estimate has higher power than other well-known competitors under heavy tailed alternatives which are frequently used in many financial applications.
Abstract: This paper proposes a new class of estimators of an unknown entropy of random vector Its asymptotic unbiasedness and consistency are proved Further, this class of estimators is used to build both goodness-of-fit and independence tests based on sample entropy A simulation study indicates that the test involving the proposed entropy estimate has higher power than other well-known competitors under heavy tailed alternatives which are frequently used in many financial applications

Journal ArticleDOI
TL;DR: This paper is aimed at assessing the effectiveness of the proposed PSO-based approach in locating, shaping, and reconstructing the dielectric parameters of unknown two-dimensional scatterers in microwave-imaging applications.
Abstract: A computational approach based on an innovative stochastic algorithm, namely, the particle swarm optimizer (PSO), is proposed for the solution of the inverse-scattering problem arising in microwave-imaging applications. The original inverse-scattering problem is reformulated in a global nonlinear optimization one by defining a suitable cost function, which is minimized through a customized PSO. In such a framework, this paper is aimed at assessing the effectiveness of the proposed approach in locating, shaping, and reconstructing the dielectric parameters of unknown two-dimensional scatterers. Such an analysis is carried out by comparing the performance of the PSO-based approach with other state-of-the-art methods (deterministic, as well as stochastic) in terms of retrieval accuracy, as well as from a computational point-of-view. Moreover, an integrated strategy (based on the combination of the PSO and the iterative multiscaling method) is proposed and analyzed to fully exploit complementary advantages of nonlinear optimization techniques and multiresolution approaches. Selected numerical experiments concerning dielectric scatterers different in shape, dimension, and dielectric profile, are performed starting from synthetic, as well as experimental inverse-scattering data.

Proceedings ArticleDOI
11 Jul 2005
TL;DR: It is shown that the proposed technique for the automated synthesis of new composite Web services can scale up to cases in which the manual development of BPEL4WS composite services is not trivial and is time consuming.
Abstract: In this paper we propose a technique for the automated synthesis of new composite Web services. Given a set of abstract BPEL4WS descriptions of component services, and a composition requirement, we automatically generate an executable BPEL4WS process that, once deployed, is able to interact with the components to satisfy the requirement. We implement the proposed approach exploiting efficient synthesis techniques, and experiment with some case studies taken from real world applications and with a parameterized domain. We show that the technique can scale up to cases in, which the manual development of BPEL4WS composite services is not trivial and is time consuming.

Journal ArticleDOI
TL;DR: In this paper, the Anderson localized modes are observed as narrow high-transmission peaks in the transmission spectrum, whereas the average of the logarithm of the transmission coefficient decreases linearly with thickness.
Abstract: We report on the observation of nonlocalized modes or necklace states of light waves in disordered systems in the Anderson localized regime. The samples consist of positional-disordered binary multilayer systems. Anderson localized modes manifest themselves as narrow high-transmission peaks in the transmission spectrum, whereas the average of the logarithm of the transmission coefficient decreases linearly with thickness. Optical necklace states are observed as modes with a characteristic multiresonance time response and relatively fast decay time.

Journal ArticleDOI
TL;DR: In this paper, the authors evaluated the opportunities provided by the use of Carbon Fiber Reinforced Polymer (CFRP) composites for the seismic repair of reinforced concrete (RC) structures on a full-scale dual system subjected to pseudodynamic tests in the ELSA laboratory.