1,720,958 research outputs found
Application of reverse engineering techniques for the analysis of orthodontic models
No full textIl settore bio-medicale è un campo in cui l’utilizzo di tecniche di Reverse Engineering porta molteplici vantaggi. In questo lavoro si presenta un’applicazione del RE in ambito ortodontico, finalizzato all’analisi della morfologia del palato. Principale problema in questa tipologia di analisi è la definizione di una procedura ripetibile per la ricostruzione del modello matematico e per l’ottenimento di parametri significativi al variare della morfologia dovuta alla crescita del soggetto. Lo studio è rivolto in particolare all’analisi del volume e dei parametri della superficie delimitata dal colletto. Si illustra inoltre l’ottimizzazione della procedura finalizzata alla riduzione delle esigenze hardware e software necessarie senza penalizzare la precisione dei risultati finali. Il metodo proposto è stato utilizzato nell’analisi delle variazioni morfologiche del palato di pazienti affetti da Palatoschisi, curati mediante l’utilizzo della tecnica del disgiuntore rapido, e nello studio degli effetti a lungo termine dell’intubazione neo natale. Per entrambi i casi si riportano i risultati geometrici principali
Measurement accuracy improvement of laser-based CMM
No full textIn the last years, a wide attention to the methodologies for the reverse engineering (RE) has been given, as an answer to the increased interest in the industrial and scientific fields. The reverse engineering is always envisaged as a technology focused on the selection of the digitalization equipment and on the software tools for the manipulation of the data and the reconstruction of the surface: the technological aspects are not considered therefore of it the demands work them relating the object. At the Dipartimento di Architettura Urbanistica e Rilevamento of the University of Padova, it is in course the "project Functional Integrated Reverse Engineering", finalized to the realization of a new technological workplace for the reverse engineering of prototypes and industrial products. This ambient consists of hardware technologies, based on a CMM Laser, and of software technologies. A critical aspect, in the phase of reconstruction of geometric feature, is the accuracy of the acquisition system that can be obtained with the precision of the workings and the methods of assemblage. Its however possible to increase the precision of the acquired data by means of the modeling of the geometric errors of the system, and numerous are the relevant scientific contributions. This job describes the application and the elaboration of a mathematical model based on the cinematic of the rigid bodies, for the correction of the geometric errors of the machine of measure to scansion laser used for the acquisition of small archaeological biomedicali and mechanical manufacts.. The model of compensation of the geometric errors is realized with the direct method, measuring the motion of the movement guides using an external device. Every error has been acquired experimentally using a commercial CMM which metrological reference. The proposed model is therefore an elaboration of the direct mapping of the positions assumed from the system in its movements to the inside of the working volume. In the following pages they introduce the mathematical model, the process of acquisition of the experimental data and the analysis of the characteristics of the CMM Laser. Finally they are introduced the results of the validation of the system using a calibrated artefact, specifically realized
Dark energy and dark matter
No full textIt is a puzzle why the densities of dark matter and dark energy are nearly equal today when they scale so differently during the expansion of the universe. This conundrum may be solved if there is a coupling between the two dark sectors. In this Letter we assume that dark matter is made of cold relics with masses depending exponentially on the scalar field associated to dark energy. Since the dynamics of the system is dominated by an attractor solution, the dark matter particle mass is forced to change with time as to ensure that the ratio between the energy densities of dark matter and dark energy become a constant at late times and one readily realizes that the present-day dark matter abundance is not very sensitive to its value when dark matter particles decouple from the thermal bath. We show that the dependence of the present abundance of cold dark matter on the parameters of the model differs drastically from the familiar results where no connection between dark energy and dark matter is present. In particular, we analyze the case in which the cold dark matter particle is the lightest supersymmetric particle. © 2003 Elsevier B.V. All rights reserved
Analisi Di Tolleranze Di Componenti Deformabili: Validazione Di Uno Strumento CAT
No full textNella progettazione di componenti meccanici un ruolo sempre più importante è svolto dagli strumenti di prototipazione virtuale. In particolare, oltre ai comuni strumenti FEM per l’analisi strutturale, si stanno diffondendo strumenti di Computer Aided Tolerancing per l’analisi di catene di tolleranze dimensionali e geometriche in ambiente CAD. Solo recentemente, tuttavia, sono apparsi i primi strumenti di analisi della propagazione della variabilità geometrica e dimensionale, che tengano conto di un aspetto fondamentale del comportamento dei corpi nella fase di assemblaggio: la loro deformabilità.
Per potere prendere in considerazione questo aspetto è necessario affiancare ai metodi di analisi delle tolleranze uno strumento FEM adatto a gestire la risoluzione di problemi di deformazione che possano avvenire durante la fase di assemblaggio. Le deformazioni in gioco durante la fase di assemblaggio, pur trascurabili per la maggior parte dei componenti, svolgono un ruolo molto importante per prodotti dalla spiccata geometria bidimensionale, schematizzabili come gusci sottili. Questi componenti, in genere in materiale plastico o lamiera, hanno un vasto utilizzo in settori produttivi chiave come l’industria aeronautica e automobilistica.
In questo lavoro si presenta una metodologia per la validazione di un applicativo per l’analisi delle tolleranze in assiemi di componenti deformabili: TAA prodotto dalla Dassault Systemes e disponibile nel suo pacchetto di modellazione Catia V5. E’ stato in particolare testato su un semplice assieme realizzato con lamiere in alluminio. A fianco della simulazione numerica è stata eseguita una campagna di misurazione sperimentale, mediante l’impiego di una macchina di misura a coordinate (CMM) basata su sensore a contatto, mettendo a confronto i risultati ottenuti
Collaborative design and manufacturing of a customizable voice prosthesis
No full textAn innovative approach to the development of biomedical devices must be intrinsically collaborative, because it requires a strict correlation among medical specialists and engineers, and a careful calibration of Rapid Prototyping and Rapid Tooling techniques in order to account for the required prosthesis design optimisation, customisation and lead time. In this paper, besides a discussion on some critical aspects relevant to the collaborative development of a voice prosthesis, some preliminary results on the functional design and the analysis of the fitting conditions of a composite mold manufactured using Rapid Prototyping (RP) techniques will be presented
An integrated tool for geometric reconstruction of functional surfaces
No full textAt Laboratory of Design Tools and Methods in Industrial Engineering, University of Padova, the FIRE project "Functional Integrated Reverse Engineering" was started, which focuses in the realisation of a novel technological environment for performing the reverse engineering of functional prototypes or products. This environment consists of hardware technologies, a multi-probes system integrated ina 5-axis machine, and of software technologies, a software module aimed at phases of pre-processing, correction and analysis of the acquired data. In the present work, an introduction to the project is given together with the description of the equipment and the software module characteristics already set up, with some example of recostruction of functional surfaces
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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