Publications

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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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Authors: Smith, AG;

Journal: English

Published: title_year

DOI: WOS:000265844200013

Pages: 188-Information Access through Search Engines and Digital Libraries

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Authors: Pretto, I; Ruffieux, S; Menon, C; Ijspeert, AJ; Cocuzza, S; Sch Engn Sci; Sch Engn Sci; Biol Inspired Res Grp; CISAS G Colombo Ctr Studies & Activ Space; Bio-inspired climbing robots relying on adhesion systems are believed to become essential tools for several industrial applications in the near future. In recent years, research has mainly focused on modeling micro-scale adhesion phenomena; a macro-scale adhesion model has however to be developed for the design of macro-scale systems. In this paper a macro-model of adhesion suitable for real-time applications is presented; it relies on a continuous representation of adhesion. An extension of the von Mises criterion is proposed as failure adhesion criterion in order to estimate the occurrence of detachment at any point of the contacting surface. An experimental set up has been designed in order to define the parameters of the model. A semi-automatic process has been developed to ensure repeatability and accuracy of the results. Polydimethylsiloxane (PDMS), which has revealed promising adhesive features for robotic use, has been used during the experimental phase. The macro-model of adhesion has been implemented in a multi-body dynamics environment based on Open Dynamics Engine (ODE) to simulate a spider-inspired robot. Simulations based on this model are suitable to represent the behaviour of climbing robots and also to optimize their design. © 2008 Jilin University. Pretto; Ruffieux; Menon; Ijspeert; Cocuzza

Journal: English

Published: doi

DOI: WOS:000260115200017

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Volume: JOURNAL OF BIONIC ENGINEERING###1672-6529 Pages: 105-A Point-Wise Model of Adhesion Suitable for Real-Time Applications of Bio-Inspired Climbing Robots

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Authors: Peserico, E; Pretto, L; Dip Ing Informaz; Dip Ing Informaz; This paper explores the fundamental question of how many iterations the celebrated HITS algorithm requires on a general graph to converge in score and, perhaps more importantly, in rank (i.e. to "get right" the order of the nodes). We prove upper and almost matching lower bounds. We also extend our results to weighted graphs. © 2009 Springer Berlin Heidelberg. Peserico; Pretto

Journal: English

Published: doi

DOI: WOS:000269148100035

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Pages: 357-HITS Can Converge Slowly, but Not Too Slowly, in Score and Rank

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Authors: Peserico, E; Pretto, L; Dip Ing Informaz; Dip Ing Informaz; How many iterations does the (ever more) popular HITS algorithm require to converge in score and, perhaps more importantly, in rank (i.e. to get the nodes of a graph "in the right order")? After pinning down the elusive notion of convergence in rank we provide the first non-trivial bounds on the convergence of HITS. A "worst case" example, requiring a number of iterations superexponential in the size of the target graph to achieve even "mild" convergence, suggests the need for greater caution in the experimental evaluation of the algorithm - as recent results of poor performance (e.g. vs. SALSA) might be due to insufficient iterations, rather than to an intrinsic deficiency of HITS. An almost matching upper bound shows that, as long as one employs exponential acceleration e.g. through a "squaring trick", a polynomial running time (practical in many application domains) always provides strong convergence guarantees. Peserico; Pretto

Journal: English

Published: doi

DOI: WOS:000270976500152

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Pages: 771-Score and Rank Convergence of HITS