A Novel Index to Compare the Representation Quality of Objects Approximated with Spheres

Practical collision detection problems require very fast algorithms. The quality of the object representation plays a key role in the efficiency of these algorithms. In this paper a new index is presented which makes it possible to compare in terms of quality of representation different algorithms that approximate an object by means of spheres. Comparative results with other indexes are provided

Nuovo codice di calcolo per lo studio del contatto tra elementi elastici ed elementi rigidi

This paper presents a new tool to find the spatial configuration of a mechanical system which comprises elastic fibres interacting both with each other and/or with rigid bodies. The configuration is determined by means of the principle of the minimum elastic potential energy of the system. Coulomb friction is neglected at the contacts. The paper gives an overview on the optimal representation of the rigid body shapes in the collison detection problem. In particular, the paper presents an elastic fiber model and describes the rigid body representation adopted. Both have been implemented in the tool. Finally an application of the tool to the biomechanical field is presented which makes it possible to find the spatial configuration of the human ligaments at the ankle joint complex

Sulla qualità di rappresentazione di oggetti approssimati mediante primitive sferiche

Nell’ambito della verifica di collisione fra corpi l’efficienza degli algoritmi gioca un ruolo fondamentale congiuntamente alla precisione nella valutazione dei contatti. Molte delle tecniche adottate in letteratura per risolvere tale problematica si basano sull’approssimazione degli oggetti in studio mediante l’uso di primitive elementari quali, ad esempio, sfere. Efficienza e precisione degli algoritmi sono aspetti strettamente correlati alla qualità di rappresentazione degli oggetti. In questo lavoro viene presentato un nuovo indice che confronta, in termini di qualità di rappresentazione, i differenti algoritmi che approssimano un oggetto mediante primitive sferiche. La validazione dei risultati viene ottenuta attraverso l’analisi ed il confronto con altri indici presenti in letteratura. La validità dell’indice proposto viene infine messa in luce da un’applicazione ad un corpo a geometria complessa quale è la tibiotarsica umana. Both algorithm efficiency and contact evaluation accuracy play a key role when dealing with the problem of Collision Detection. Several techniques from the literature used to solve this problem are based on the object representation by means of spheres. Efficiency and precision of the algorithms are closely connected to the quality of the representation of the objects. In this report, a new index which evaluates the approximation quality of the representation of the object with spheres is presented. Comparing the proposed index with other indexes from previous researches proves its correctness. Finally, as an example of application to a complex geometry bone, from the human ankle highlights the efficiency of the index

Editorial: PsychOncology: clinical psychology for cancer patients—Cancer: the key role of clinical psychology

PsychOncology: clinical psychology for cancer patients-Cancer: the key role of clinical psycholog

Genetic algorithms for finding episodes in temporal networks

Castelli, M., Dondi, R., & Hosseinzadeh, M. M. (2020). Genetic algorithms for finding episodes in temporal networks. Procedia Computer Science, 176, 215-224. https://doi.org/10.1016/j.procs.2020.08.023The evolution of networks is a fundamental topic in network analysis and mining. One of the approaches that has been recently considered in this field is the analysis of temporal networks, where relations between elements can change over time. A relevant problem in the analysis of temporal networks is the identification of cohesive or dense subgraphs since they are related to communities. In this contribution, we present a method based on genetic algorithms and on a greedy heuristic to identify dense subgraphs in a temporal network. We present experimental results considering both synthetic and real-networks, and we analyze the performance of the proposed method when varying the size of the population and the number of generations. The experimental results show that our heuristic generally performs better in terms of quality of the solutions than the state-of-art method for this problem. On the other hand, the state-of-art method is faster, although comparable with our method, when the size of the population and the number of generations are limited to small values.publishersversionpublishe

The Longest Filled Common Subsequence Problem

Inspired by a recent approach for genome reconstruction from incomplete data, we consider a variant of the longest common subsequence problem for the comparison of two sequences, one of which is incomplete, i.e. it has some missing elements. The new combinatorial problem, called Longest Filled Common Subsequence, given two sequences A and B, and a multiset M of symbols missing in B, asks for a sequence B* obtained by inserting the symbols of M into B so that B* induces a common subsequence with A of maximum length. First, we investigate the computational and approximation complexity of the problem and we show that it is NP-hard and APX-hard when A contains at most two occurrences of each symbol. Then, we give a 3/5 approximation algorithm for the problem. Finally, we present a fixed-parameter algorithm, when the problem is parameterized by the number of symbols inserted in B that "match" symbols of A

10th Workshop on Biomedical and Bioinformatics Challenges for Computer Science - BBC2017

Agapito, G., Cannataro, M., Castelli, M., Dondi, R., & Zoppis, I. (2017). 10th Workshop on Biomedical and Bioinformatics Challenges for Computer Science - BBC2017. Procedia Computer Science, 108, 1113-1114. https://doi.org/10.1016/j.procs.2017.05.279We present the 10th Workshop on Biomedical and Bioinformatics Challenges for Computer Science - BBC2017, held in Zurich, 12 - 14 June 2017.publishersversionpublishe