Showing papers by "University of Trento published in 2009"
TL;DR: A seminal view on recent advances in techniques for hyperspectral image processing, focusing on the design of techniques able to deal with the high-dimensional nature of the data, and to integrate the spa- tial and spectral information.
1,481 citations
TL;DR: In this paper, a review of the recent theoretical and experimental advances in the study of ultra-cold gases made of bosonic particles interacting via the long-range, anisotropic dipole-dipole interaction, in addition to the short-range and isotropic contact interaction usually at work in ultracold gases is presented.
Abstract: This paper reviews the recent theoretical and experimental advances in the study of ultra-cold gases made of bosonic particles interacting via the long-range, anisotropic dipole–dipole interaction, in addition to the short-range and isotropic contact interaction usually at work in ultra-cold gases. The specific properties emerging from the dipolar interaction are emphasized, from the mean-field regime valid for dilute Bose–Einstein condensates, to the strongly correlated regimes reached for dipolar bosons in optical lattices. (Some figures in this article are in colour only in the electronic version)
1,230 citations
10 Feb 2009
TL;DR: UkWaC, deWaC and itWaC are introduced, three very large corpora of English, German, and Italian built by web crawling, and the methodology and tools used in their construction are described.
Abstract: This article introduces ukWaC, deWaC and itWaC, three very large corpora of English, German, and Italian built by web crawling, and describes the methodology and tools used in their construction. The corpora contain more than a billion words each, and are thus among the largest resources for the respective languages. The paper also provides an evaluation of their suitability for linguistic research, focusing on ukWaC and itWaC. A comparison in terms of lexical coverage with existing resources for the languages of interest produces encouraging results. Qualitative evaluation of ukWaC versus the British National Corpus was also conducted, so as to highlight differences in corpus composition (text types and subject matters). The article concludes with practical information about format and availability of corpora and tools.
1,132 citations
TL;DR: The Crystallography Open Database is an ongoing initiative by crystallographers to gather all published inorganic, metal–organic and small organic molecule structures in one database, providing a straightforward search and retrieval interface.
Abstract: The Crystallography Open Database (COD), which is a project that aims to gather all available inorganic, metal–organic and small organic molecule structural data in one database, is described. The database adopts an open-access model. The COD currently contains ∼80 000 entries in crystallographic information file format, with nearly full coverage of the International Union of Crystallography publications, and is growing in size and quality.
1,124 citations
TL;DR: In this article, the magnetic field emerging in heavy-ion collisions has the magnitude of the order of $eB_y \sim 10^{-1} \cdot m_\pi^2$ for the SPS energy range and $b_y ǫ \sim m_ \pi^ 2$ for RHIC energies.
Abstract: Magnetic fields created in the noncentral heavy-ion collision are studied within a microscopic transport model, namely the Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). Simulations were carried out for different impact parameters within the SPS energy range (Elab = 10-158A GeV) and for highest energies accessible for RHIC. We show that the magnetic field emerging in heavy-ion collisions has the magnitude of the order of $eB_y \sim 10^{-1} \cdot m_\pi^2$ for the SPS energy range and $eB_y \sim m_\pi^2$ for the RHIC energies. The estimated value of the magnetic field strength for the LHC energy amounts to $eB_y\sim 15 \cdot m_\pi^2$.
939 citations
TL;DR: In this article, the existence of superfluidity in polaritons is investigated in terms of the Landau criterion and manifests itself as the suppression of scattering from defects when the flow velocity is slower than the speed of sound in the fluid.
Abstract: Similar to atoms in cold gases, exciton–polaritons in semiconductor microcavities can undergo Bose–Einstein condensation. A striking consequence of the appearance of macroscopic coherence in these systems is superfluidity. Now, clear evidence for such behaviour has been found in an exciton–polariton condensate. Superfluidity, the ability of a quantum fluid to flow without friction, is one of the most spectacular phenomena occurring in degenerate gases of interacting bosons. Since its first discovery in liquid helium-4 (refs 1, 2), superfluidity has been observed in quite different systems, and recent experiments with ultracold trapped atoms have explored the subtle links between superfluidity and Bose–Einstein condensation3,4,5. In solid-state systems, it has been anticipated that exciton–polaritons in semiconductor microcavities should behave as an unusual quantum fluid6,7,8, with unique properties stemming from its intrinsically non-equilibrium nature. This has stimulated the quest for an experimental demonstration of superfluidity effects in polariton systems9,10,11,12,13. Here, we report clear evidence for superfluid motion of polaritons. Superfluidity is investigated in terms of the Landau criterion and manifests itself as the suppression of scattering from defects when the flow velocity is slower than the speed of sound in the fluid. Moreover, a Cerenkov-like wake pattern is observed when the flow velocity exceeds the speed of sound. The experimental findings are in quantitative agreement with predictions based on a generalized Gross–Pitaevskii theory12,13, and establish microcavity polaritons as a system for exploring the rich physics of non-equilibrium quantum fluids.
820 citations
TL;DR: The analysis singles out the class of entangled states which are useful to overcome classical phase sensitivity in metrology and sensors and studies the creation of useful entangled states by the nonlinear dynamical evolution of two decoupled Bose-Einstein condensates or trapped ions.
Abstract: We show that the quantum Fisher information provides a sufficient condition to recognize multi-particle entanglement in a N qubit state. The same criterion gives a necessary and sufficient condition for sub shot-noise phase sensitivity in the estimation of a collective rotation angle θ . The analysis therefore singles out the class of entangled states which are {\it useful} to overcome classical phase sensitivity in metrology and sensors. We finally study the creation of useful entangled states by the non-linear dynamical evolution of two decoupled Bose-Einstein condensates or trapped ions.
703 citations
09 Oct 2009
TL;DR: The key features of peer-to-peer (P2P) systems are scalability and dynamism, so simulation is crucial in P2P research.
Abstract: The key features of peer-to-peer (P2P) systems are scalability and dynamism. The evaluation of a P2P protocol in realistic environments is very expensive and difficult to reproduce, so simulation is crucial in P2P research.
617 citations
TL;DR: An efficient version of the RLDA recently presented by Ye to cope with critical ill-posed hyperspectral image classification problems is introduced in the remote sensing community and several LDA-based classifiers are compared theoretically and experimentally with the standard LDA and theRLDA.
Abstract: This paper analyzes the classification of hyperspectral remote sensing images with linear discriminant analysis (LDA) in the presence of a small ratio between the number of training samples and the number of spectral features. In these particular ill-posed problems, a reliable LDA requires one to introduce regularization for problem solving. Nonetheless, in such a challenging scenario, the resulting regularized LDA (RLDA) is highly sensitive to the tuning of the regularization parameter. In this context, we introduce in the remote sensing community an efficient version of the RLDA recently presented by Ye to cope with critical ill-posed problems. In addition, several LDA-based classifiers (i.e., penalized LDA, orthogonal LDA, and uncorrelated LDA) are compared theoretically and experimentally with the standard LDA and the RLDA. Method differences are highlighted through toy examples and are exhaustively tested on several ill-posed problems related to the classification of hyperspectral remote sensing images. Experimental results confirm the effectiveness of the presented RLDA technique and point out the main properties of other analyzed LDA techniques in critical ill-posed hyperspectral image classification problems.
568 citations
Charles University in Prague1, Google2, University of Trento3, National Institute of Information and Communications Technology4, University of Barcelona5, Polytechnic University of Catalonia6, New York University7, Uppsala University8, University of Stuttgart9, Stanford University10, Brandeis University11, Saarland University12
TL;DR: This shared task combines the shared tasks of the previous five years under a unique dependency-based formalism similar to the 2008 task and describes how the data sets were created and show their quantitative properties.
Abstract: For the 11th straight year, the Conference on Computational Natural Language Learning has been accompanied by a shared task whose purpose is to promote natural language processing applications and evaluate them in a standard setting. In 2009, the shared task was dedicated to the joint parsing of syntactic and semantic dependencies in multiple languages. This shared task combines the shared tasks of the previous five years under a unique dependency-based formalism similar to the 2008 task. In this paper, we define the shared task, describe how the data sets were created and show their quantitative properties, report the results and summarize the approaches of the participating systems.
531 citations
TL;DR: Results suggest that volumes derived from automated segmentation of T1-weighted structural images are reliable measures within the same scanner platform, even after upgrades; however, combining data across platform and across field-strength introduces a bias that should be considered in the design of multi-site studies, such as clinical drug trials.
TL;DR: In this paper, radio-frequency magnetron sputtering and a sol-gel method were used to study hydrogen generation by photocatalytic water-splitting under visible light irradiation.
TL;DR: In this article, the authors provide a comprehensive overview of the existing literature in this subject area and focus on the legal implementation of social enterprises, concluding that the lack of a common understanding of social enterprise should not be regarded as a limitation as such debate encourages a rethinking of the theoretical definition of enterprise and its legal structure.
Abstract: – The purpose of this paper is to analyze the evolution of the social enterprise concept at an international level. It provides a comprehensive overview of the existing literature in this subject area and focuses on the legal implementation of social enterprises., – The paper is an analytic review, building on previous work. Conclusions are on how the social enterprise concept has been legally implemented in a number of representative European countries., – The lack of a common understanding of social enterprise should not be regarded as a limitation as such debate encourages a rethinking of the theoretical definition of enterprise and its legal structure. The legal recognition of social enterprise contributes to conceptual clarification in the countries concerned., – This is a conceptual discussion paper, which stimulates further research on the most interesting mechanisms and consistent models of social enterprise that are developing at an international level., – The paper synthesises existing conceptual studies on social enterprise. It contributes to enrich the current debate on social enterprise and aids in focusing future research.
13 Apr 2009
TL;DR: It is shown that the system deployed in Torre Aquila, a medieval tower in Trento, is an effective tool for assessing the tower's stability, as it delivers data reliably and has an estimated lifetime beyond one year.
Abstract: Wireless sensor networks are untethered infrastructures that are easy to deploy and have limited visual impact—a key asset in monitoring heritage buildings of artistic interest. This paper describes one such system deployed in Torre Aquila, a medieval tower in Trento (Italy). Our contributions range from the hardware to the graphical front-end. Customized hardware deals efficiently with high-volume vibration data, and specially-designed sensors acquire the building's deformation. Dedicated software services provide: i) data collection, to efficiently reconcile the diverse data rates and reliability needs of heterogeneous sensors; ii) data dissemination, to spread configuration changes and enable remote tasking; iii) time synchronization, with low memory demands. Unlike most deployments, built directly on the operating system, our entire software layer sits atop our TeenyLIME middleware. Based on 4 months of operation, we show that our system is an effective tool for assessing the tower's stability, as it delivers data reliably (with loss ratios ≪0.01%) and has an estimated lifetime beyond one year.
TL;DR: A new robust and accurate SPH scheme, able to track correctly complex three-dimensional non-hydrostatic free surface flows and, even more important, also able to compute an accurate and little oscillatory pressure field, which can handle any moving rigid body with arbitrarily irregular geometry is proposed.
TL;DR: The findings demonstrate that the medial-to-lateral bias by conceptual domain in the ventral visual pathway does not require visual experience in order to develop and suggest the operation of innately determined domain-specific constraints on the organization of object knowledge.
TL;DR: In this article, the authors studied the statistical properties of the web of import-export relationships among world countries using a weighted-network approach and found that the distribution of positive link weights is slowly moving from a log-normal density towards a power law.
Abstract: This paper studies the statistical properties of the web of import-export relationships among world countries using a weighted-network approach. We analyze how the distributions of the most important network statistics measuring connectivity, assortativity, clustering, and centrality have coevolved over time. We show that all node-statistic distributions and their correlation structure have remained surprisingly stable in the last 20 years—and are likely to do so in the future. Conversely, the distribution of positive link weights is slowly moving from a log-normal density towards a power law. We also characterize the autoregressive properties of network-statistics dynamics. We find that network-statistics growth rates are well-proxied by fat-tailed densities like the Laplace or the asymmetric exponential power. Finally, we find that all our results are reasonably robust to a few alternative, economically meaningful, weighting schemes.
TL;DR: In this article, the microstructural and mechanical characterization of a biomedical Ti•6Al•4V alloy produced by electron beam melting, and the study of the stability of the as-built microstructure upon heat treatment are presented.
Abstract: Purpose – The purpose of this paper is the microstructural and mechanical characterization of a biomedical Ti‐6Al‐4V alloy produced by electron beam melting, and the study of the stability of the as‐built microstructure upon heat treatment.Design/methodology/approach – Ti‐6Al‐4V alloy produced by electron beam melting has been mechanically characterized through tensile and fatigue testing. Its microstructure has been investigated by optical observation after etching and by X‐ray diffractometry analysis. The stability of the microstructure of the as‐built material has been deepened carrying out suitable heat treatments, after an analysis by dilatometry test.Findings – The microstructure of a Ti‐6Al‐4V alloy produced by electron beam melting has a very fine and acicular morphology, because of the intrinsically high‐solidification rate of the process. This microstructure is very stable, and the traditional thermal treatments cannot modify it; the microstructure changes significantly only when an amount of st...
TL;DR: In this paper, the authors investigate the ongoing process of labour market "flexibilization" and its consequences for individual labour market careers and social inequalities and ask whether the deregulation has fulfilled the expectations attached to it.
Abstract: Labor market 'flexibilization' or 'deregulation' is seen by many as a requirement for economic and occupational growth. As one route towards more flexibility, many European countries increased the so-called atypical or non-standard forms of employment while leaving the regulation of existing employment relations largely unchanged. In Italy, this led to a strong segmentation of the labour market. As employment is the only connection to a series of welfare entitlements, this praxis might lead to strong cleavages in the society. In this paper, we investigate the ongoing process of labour market 'flexibilization' and its consequences for individual labour market careers and social inequalities and ask whether the deregulation has fulfilled the expectations attached to it. In detail, we study the entries into the marginal labour market and the consequences for employment careers of these forms of 'new' flexible employment. Empirical findings based on Indagine Longitudinale sulle Famiglie Italiane data cast doubts on the effectiveness of the specific form of market deregulation in Italy and confirm strong long-term implications of atypical employment episodes for career chances.
29 Jun 2009
TL;DR: It is shown that the optimal strategy is different from the fixed one, and supports more effective and efficient interaction sessions, and allows conversational systems to autonomously improve a fixed strategy and eventually learn a better one using reinforcement learning techniques.
Abstract: Conversational recommender systems (CRSs) assist online users in their information-seeking and decision making tasks by supporting an interactive process. Although these processes could be rather diverse, CRSs typically follow a fixed strategy, e.g., based on critiquing or on iterative query reformulation. In a previous paper, we proposed a novel recommendation model that allows conversational systems to autonomously improve a fixed strategy and eventually learn a better one using reinforcement learning techniques. This strategy is optimal for the given model of the interaction and it is adapted to the users' behaviors. In this paper we validate our approach in an online CRS by means of a user study involving several hundreds of testers. We show that the optimal strategy is different from the fixed one, and supports more effective and efficient interaction sessions.
04 Jul 2009
TL;DR: This chapter presents algorithms for both schema mapping creation via query discovery, and for query generation for data exchange that can be used in pure relational, pure XML, nested relational, or mixed relational and nested contexts.
Abstract: The Clio project provides tools that vastly simplify information integration. Information integration requires data conversions to bring data in different representations into a common form. Key contributions of Clio are the definition of non-procedural schema mappings to describe the relationship between data in heterogeneous schemas, a new paradigm in which we view the mapping creation process as one of query discovery, and algorithms for automatically generating queries for data transformation from the mappings. Clio provides algorithms to address the needs of two major information integration problems, namely, data integration and data exchange . In this chapter, we present our algorithms for both schema mapping creation via query discovery, and for query generation for data exchange. These algorithms can be used in pure relational, pure XML, nested relational, or mixed relational and nested contexts.
TL;DR: In this article, a historical and conceptual analysis of multi-level governance (MLG) is performed in order to tease out its characterizing traits and allow for its utilization for both empirical and normative purposes.
Abstract: In this paper I perform a historical and conceptual analysis of multi‐level governance (MLG) in order to tease out its characterizing traits and allow for its utilization for both empirical and normative purposes MLG is a dynamic three‐dimensional concept that blurs and problematizes three analytical distinctions that have been central to the conventional reflection on the European modern state: (1) that between centre and periphery, (2) that between state and society and (3) that between the domestic and the international Each dimension or axis involves, in its turn, changes that occur at three analytical levels: political mobilization, policy‐making and polity restructuring Through the combination of these dimensions I generate a three‐dimensional conceptual space within which the empirical scope and reach of MLG can be gauged and its desirability in normative terms assessed
TL;DR: The paper presents extensive empirical analysis of the protocol along with theoretical analysis of certain aspects of its behavior, and describes a practical application of T-Man for building Chord distributed hash table overlays efficiently from scratch.
TL;DR: Experimental results show that the proposed pattern-recognition system to identify and classify buried objects from ground-penetrating radar (GPR) imagery exhibits promising performances both in terms of object detection and material recognition.
Abstract: In this paper, we propose a novel pattern-recognition system to identify and classify buried objects from ground-penetrating radar (GPR) imagery. The entire process is subdivided into four steps. After a preprocessing step, the GPR image is thresholded to put under light the regions containing potential objects. The third step of the system consists of automatically detecting the objects in the obtained binary image by means of a search of linear/hyperbolic patterns formulated within a genetic optimization framework. In the genetic optimizer, each chromosome models the apex position and the curvature associated with the candidate pattern, while the fitness function expresses the Hamming distance between that pattern and the binary image content. Finally, in the fourth step, the problem of the recognition of the material type of the identified objects is approached as a classification issue, which is solved by means of an opportune feature-extraction strategy and a support vector machine classifier. To illustrate the performances of the proposed system, we conducted a thorough experimental study based on GPR images generated by a GPR simulator based on the finite-difference time-domain method so as to construct different acquisition scenarios by varying the number of buried objects, their position, their size, their shape, and their material type. In general, the obtained experimental results show that the proposed system exhibits promising performances both in terms of object detection and material recognition.
TL;DR: Logopenic progressive aphasia and posterior cortical atrophy showed largely overlapping anatomic and biologic features with early age at onset of Alzheimer disease, suggesting that these clinical syndromes represent the spectrum of clinical manifestation of the nontypical form of Alzheimer Disease that presents at an early age.
Abstract: Objective: Posterior cortical atrophy (PCA) and logopenic progressive aphasia (LPA) are clinical syndromes associated with posterior brain atrophy. We compared PCA and LPA to each other and to an age-matched group of patients with early age at onset of Alzheimer disease (EO-AD). We hypothesized that these 3 syndromes are part of a single clinical and biologic continuum. Methods: Voxel-based morphometry (VBM) was used to assess atrophy in 14 PCA, 10 LPA, and 16 EO-AD patients compared to 65 healthy controls. Genetic analysis for APOE was conducted in 30 patients and 44 controls. Four patients came to autopsy. An additional 14 were studied with the beta-amyloid specific PET with tracer 11 C-labeled Pittsburgh Compound-B (PIB). Results: VBM results demonstrated that, compared to controls, each patient group showed a large area of overlapping atrophy in bilateral parietal, occipital, precuneus, posterior cingulate, posterior temporal, and hippocampal regions. Surrounding this common area, group-specific atrophy was found in small, symptom-specific regions for each group: the right ventral-occipital and superior parietal regions in PCA, the left middle and superior temporal gyri in LPA, and the prefrontal cortex in EO-AD. APOE e4 frequency was higher in all patient groups compared to controls. Four PCA, 5 LPA, and 8 EO-AD patients showed evidence of cortical amyloid at pathology (n = 3) or on PIB-PET (n = 14). Conclusions: Logopenic progressive aphasia and posterior cortical atrophy showed largely overlapping anatomic and biologic features with early age at onset of Alzheimer disease, suggesting that these clinical syndromes represent the spectrum of clinical manifestation of the nontypical form of Alzheimer disease that presents at an early age. AD = Alzheimer disease; CBD = corticobasal degeneration; EO-AD = early age at onset of Alzheimer disease; LPA = logopenic progressive aphasia; MAC = Memory and Aging Center; PCA = posterior cortical atrophy; PIB = Pittsburgh Compound-B; PPA = primary progressive aphasia; UCSF = University of California San Francisco; VBM = voxel-based morphometry.
TL;DR: Failure to find cross-modal adaptation for executed and observed motor acts is not compatible with the core assumption of mirror neuron theory, which holds that action recognition and understanding are based on motor simulation.
Abstract: Neurons in macaque ventral premotor cortex and inferior parietal lobe discharge during both the observation and the execution of motor acts. It has been claimed that these so-called mirror neurons form the basis of action understanding by matching the visual input with the corresponding motor program (direct matching). Functional magnetic resonance imaging (fMRI) adaptation can be used to test the direct matching account of action recognition by determining whether putative mirror neurons show adaptation for repeated motor acts independently of whether they are observed or executed. An unambiguous test of the hypothesis requires that the motor acts be meaningless to ensure that any adaptation effect is directly because of movement recognition/motor execution and not contextually determined inferences. We found adaptation for motor acts that were repeatedly observed or repeatedly executed. We also found adaptation for motor acts that were first observed and then executed, as would be expected if a previously seen act primed the subsequent execution of that act. Crucially, we found no signs of adaptation for motor acts that were first executed and then observed. Failure to find cross-modal adaptation for executed and observed motor acts is not compatible with the core assumption of mirror neuron theory, which holds that action recognition and understanding are based on motor simulation.
TL;DR: A panorama on how practice-based studies (PBS) concerned with organizational learning have developed in recent years, and to describe the topics that such studies have debated, can be found in this article.
Abstract: Purpose – The aim of this introduction to the special issue is to furnish a panorama on how practice‐based studies (PBS) concerned with organizational learning have developed in recent years, and to describe the topics that such studies have debatedDesign/methodology/approach – The articles in this special issue were first presented at the standing working group on “Practice‐based Studies of Knowledge and Innovation in Workplaces” of the European Group for Organizational Studies, and will therefore provide the background to PBS and an idea of its methodologyFindings – The practice‐ based approach may be useful for: a renewed conception of organization as a texture of interrelated practices which extend to form an action‐net sustained by a knowing‐in‐action which renews itself and transforms itself into being practiced; a renewed conception of knowledge as a situated, negotiated, emergent and embedded activity; a renewed conception of materiality as a form of distributed agency and an intimate relationsh
TL;DR: This work theoretically investigates the optical response of a one-dimensional array of strongly nonlinear optical microcavities, and signatures of strong correlations are identified in the transmission spectrum of the system, as well as in the intensity correlations of the transmitted light.
Abstract: We theoretically investigate the optical response of a one-dimensional array of strongly nonlinear optical microcavities. When the optical nonlinearity is much larger than both losses and intercavity tunnel coupling, the nonequilibrium steady state of the system is reminiscent of a strongly correlated Tonks-Girardeau gas of impenetrable bosons. Signatures of strong correlations are identified in the transmission spectrum of the system, as well as in the intensity correlations of the transmitted light. Possible experimental implementations in state-of-the-art solid-state devices are discussed.
TL;DR: In this paper, the authors argue that taste is a sense of what is aesthetically fitting within a community of practitioners, a preference for "the way we do things together" and is learnt and taught as part of becoming a practitioner.
Abstract: This article aims to enhance our understanding of how practice is socially sustained, learnt and constantly refined by arguing that practice is much more than a set of activities—it involves, beside instrumental and ethical judgements, taste and appraisal. Taste is a sense of what is aesthetically fitting within a community of practitioners—a preference for ‘the way we do things together’. Taste is based on subjective attachment to the object of practice and is learnt and taught as part of becoming a practitioner; it is performed as a collective, situated activity within a practice. The elaboration of taste and the refining of practice within a community involves taste-making, which is based on ‘sensible knowledge’ and the continual negotiation of aesthetic categories. The article examines how in a variety of practices, taste-making occurs through three processes: sharing a vocabulary for appraisal; crafting identities within epistemic communities; and refining performances.