Publications

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Authors: Non assegn; AREA MIN. 11 - Scienze storiche, filosofiche, pedagogiche e psicologiche

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Authors: Non assegn; ITA

Journal: Rubettino Editore

Published: title_year

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Authors: Agosti, M; Pretto, L;; Kleinberg's HITS algorithm (Kleinberg 1999), which was originally developed in a Web context, tries to infer the authoritativeness of a Web page in relation to a specific query using the structure of a subgraph of the Web graph, which is obtained considering this specific query. Recent applications of this algorithm in contexts far removed from that of Web searching (Bacchin, Ferro and Melucci 2002, Ng et al. 2001) inspired us to study the algorithm in the abstract, independently of its particular applications, trying to mathematically illuminate its behaviour. In the present paper we detail this theoretical analysis. The original work starts from the definition of a revised and more general version of the algorithm, which includes the classic one as a particular case. We perform an analysis of the structure of two particular matrices, essential to studying the behaviour of the algorithm, and we prove the convergence of the algorithm in the most general case, finding the analytic expression of the vectors to which it converges. Then we study the symmetry of the algorithm and prove the equivalence between the existence of symmetry and the independence from the order of execution of some basic operations on initial vectors. Finally, we expound some interesting consequences of our theoretical results. © 2005 Springer Science + Business Media, Inc. Agosti; Pretto

Journal: English

Published: doi

DOI: WOS:000227178800004

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Volume: INFORMATION RETRIEVAL###1386-4564 Pages: 243-Theoretical study of a generalized version of Kleinberg's HITS algorithm

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Authors: Galletta, G; Ferri, F; Fanti, G; D'Alessandro, M; Bertoloni, G; Pavarin, D; Bettanini, C; Cozza, P; Pretto, P; Bianchini, G; Debei, S;; The Martian Environment Simulator (SAM "Simulatore di Ambiente Marziano") is a interdisciplinary project of Astrobiology done at University of Padua. The research is aimed to the study of the survival of the microorganisms exposed to the "extreme" planetary environment. The facility has been designed in order to simulate Mars' environmental conditions in terms of atmospheric pressure, temperature cycles and UV radiation dose. The bacterial cells, contained into dedicated capsules, will be exposed to thermal cycles simulating diurnal and seasonal Martian cycles. The metabolism of the different biological samples will be analysed at different phases of the experiment, to study their survival and eventual activity of protein synthesis (mortality, mutations and capability of DNA reparing). We describe the experimental facility and provide the perspectives of the biological experiments we will perform in order to provide hints on the possibility of life on Mars either autochthonous or imported from Earth. © 2006 Springer Science+Business Media, B.V. Galletta; Ferri; Fanti; D'Alessandro; Bertoloni; Pavarin; Bettanini; Cozza; Pretto; Bianchini; Debei

Journal: English

Published: doi

DOI: WOS:000243623600028

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Volume: ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE###0169-6149 Pages: 627-SAM, the Italian Martian Simulation Chamber

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Authors: Galletta, G; Ferri, F; Fanti, G; D'Alessandro, M; Bertoloni, G; Pavarin, D; Bettanini, C; Cozza, P; Pretto, P; Bianchini, G; Debei, S;; The Martian Environment Simulator (SAM "Simulatore di Ambiente Marziano") is a interdisciplinary project of Astrobiology done at University of Padua. The research is aimed to the study of the survival of the microorganisms exposed to the "extreme" planetary environment. The facility has been designed in order to simulate Mars' environmental conditions in terms of atmospheric pressure, temperature cycles and UV radiation dose. The bacterial cells, contained into dedicated capsules, will be exposed to thermal cycles simulating diurnal and seasonal Martian cycles. The metabolism of the different biological samples will be analysed at different phases of the experiment, to study their survival and eventual activity of protein synthesis (mortality, mutations and capability of DNA reparing). We describe the experimental facility and provide the perspectives of the biological experiments we will perform in order to provide hints on the possibility of life on Mars either autochthonous or imported from Earth. © 2006 Springer Science+Business Media, B.V. Galletta; Ferri; Fanti; D'Alessandro; Bertoloni; Pavarin; Bettanini; Cozza; Pretto; Bianchini; Debei

Journal: English

Published: doi

DOI: WOS:000243623600028

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Volume: ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE###0169-6149 Pages: 627-SAM, the Italian Martian Simulation Chamber

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Authors: Melucci, M; Pretto, L; Dept Informat Engn; Dept Informat Engn; As PageRank is a ranking algorithm, it is of prime interest to study the order induced by its values on webpages. In this paper a thorough mathematical analysis of PageRank-induced order changes when the damping factor varies is provided. Conditions that do not allow variations in the order are studied, and the mechanisms that make the order change are mathematically investigated. Moreover the influence on the order of a truncation in the actual computation of PageRank through a power series is analysed. Experiments carried out on a large Web digraph to integrate the mathematical analysis show that PageRank - while working on a real digraph -tends to hinder variations in the order of large rankings, presenting a high stability in its induced order both in the face of large variations of the damping factor value and in the face of truncations in its computation. © Springer-Verlag Berlin Heidelberg 2007. Melucci; Pretto

Journal: English

Published: title_year

DOI: WOS:000246044300051

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Pages: +-PageRank: When order changes

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Authors: Agosti, M; Coppotelli, T; Ferro, N; Pretto, L; Dept Informat Engn; Dept Informat Engn; The increasing number of users and the diffusion of Digital Libraries (DLs) has increased the demand for newer and improved systems to give better assistance to the user during the search of resources in collections managed by Digital Library Systems (DLSs). In this perspective, the annotations made on documents offer an interesting possibility for improving both the user experience of the DLS and the retrieval performance of the system itself. However, while different approaches based on annotations have been proposed, they still lack a full experimental evaluation, mainly because an experimental collection with annotation is missing. Therefore, this paper addresses the problem of setting an adequate experimental test-bed for DL search algorithms which exploit annotations, and discusses a flexible strategy for creating test collections with annotated documents. © Springer-Verlag Berlin Heidelberg 2007. Agosti; Coppotelli; Ferro; Pretto

Journal: English

Published: Agosti M.; Coppotelli T.; Ferro N.; Pretto L.

DOI: WOS:000252143400023

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Pages: 159-Annotations and digital libraries: Designing adequate test-beds

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Authors: Agosti, M; Coppotelli, T; Ferro, N; Pretto, L; Dept Informat Engn; Dept Informat Engn; This study addresses the lack of an adequate test collection that can be used to evaluate search systems that exploit annotations to increase the retrieval effectiveness of an information search tool. In particular, a new approach is proposed that enables the automatic creation of multiple test collections without human effort. This approach takes advantage of the human relevance assessments contained in an already existing test collection and it introduces content-level annotations in that collection. © Springer-Verlag Berlin Heidelberg 2007. Agosti; Coppotelli; Ferro; Pretto

Journal: English

Published: title_year

DOI: WOS:000252882500016

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Pages: 176-An approach for the construction of an experimental test collection to evaluate search systems that exploit annotations

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Authors: This paper presents the theoretical formulation and the experimental validation of an innovative algorithm for the kinematic inversion of redundant free-flying space robotic systems, which causes minimum attitude disturbances on the spacecrafts on which they are mounted. The subject is of particular interest because robotic systems used in space need to limit induced spacecraft attitude disturbances while performing manipulator manoeuvres in order to avoid communications problems. Reduced spacecraft attitude disturbances will result in a lower fuel consumption, and therefore in an increase of the system useful life. The proposed algorithm is based on the use of a weighted pseudo-inversion of the Jacobian matrix of the robot and is aimed at minimizing the torque transferred to the spacecraft due to the robotic arm movement during continuous end-effector path tracking. The algorithm has been tested using a 3D free-flying robot previously tested in an ESA Parabolic Flight Campaign. In this test campaign the 3D robot has been converted in a 2D robot taking advantage of its modular structure, and it has been suspended by means of air-bearings on a granite plane. In this way it is possible to perform planar tests, which have the advantage that it is possible to simulate a microgravity environment without time constraints. The base of the robot has been fixed on ground by means of a custom designed dynamometer, which measures the forces and torques transferred to ground to be minimized. The forces and torques transferred to ground using the proposed kinematic inversion method have been compared with those relevant to a classical kinematic inversion which minimizes only the joints velocities. The experimental results validated the proposed algorithm and confirmed its good performance. Cocuzza; Pretto; Menon; Angrilli

Journal: 2007

Published: Cocuzza S.; Pretto I.; Menon C.; Angrilli F.

DOI: 352573454

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Authors: This paper presents the theoretical formulation and the experimental validation of an innovative algorithm for the kinematic inversion of redundant space robotic systems aimed at minimizing the torque transferred to the spacecraft due to the robotic arm movement. The differential kinematics has been formulated at the acceleration level and an additional constraint has been imposed in order to minimize the torque transferred to the spacecraft center of mass. This problem results to be a constrained linear least squares problem and a closed form solution has been proposed for non singular trajectories. An extension of this algorithm has been presented for singular trajectories, or for non singular trajectories in which joint accelerations exceed their limits, in order to limit the joint accelerations under acceptable values. In this case the problem results to be a constrained linear least squares problem with both equality and inequality constraints, and need iterative or recursive calculations to be solved. The proposed algorithm has been experimentally tested using a 3D free-flying robot previously tested in an ESA Parabolic Flight Campaign. In this test campaign the 3D robot has been converted in a 2D robot taking advantage of its modular structure, and it has been suspended by means of air-bearings on a granite plane. In this way it is possible to perform simulated microgravity tests without time constraints. The base of the robot has been fixed on ground by means of a custom design dynamometer, which measures the torque transferred to the ground to be minimized. The experimental results validated the proposed algorithm and confirmed its good performance. Cocuzza; Pretto; Angrilli

Journal: 2008

Published: title_year

DOI: 358576037

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