187,345 research outputs found
2D-3D registration of CT vertebra volume to fluoroscopy projection: A calibration model assessment (doi:10.1155/2010/806094)
No full textThis study extends a previous research concerning intervertebral motion registration by means of 2D dynamic fluoroscopy to obtain a more comprehensive 3D description of vertebral kinematics. The problem of estimating the 3D rigid pose of a CT volume of a vertebra from its 2D X-ray fluoroscopy projection is addressed. 2D-3D registration is obtained maximising a measure of similarity between Digitally Reconstructed Radiographs (obtained from the CT volume) and real fluoroscopic projection. X-ray energy correction was performed. To assess the method a calibration model was realised a sheep dry vertebra was rigidly fixed to a frame of reference including metallic markers. Accurate measurement of 3D orientation was obtained via single-camera calibration of the markers and held as true 3D vertebra position; then, vertebra 3D pose was estimated and results compared. Error analysis revealed accuracy of the order of 0.1 degree for the rotation angles of about 1?mm for displacements parallel to the fluoroscopic plane, and of order of 10?mm for the orthogonal displacement.<br/
HRV Adaptive Spectral Estimation for Transient Detection
No full textQuantitative monitoring of cardiac autonomic control can be provided, non invasively, by of heart rate variability (HRV) analysis. The study of the HRV is finding more and more fields of application. HRV long-term and short-term analysis can be performed. Among the latter, some applications have to deal with relatively brief changes of the simpatho-vagal activity, as, for example, the study of the fetal heart rate (correlated with uterine contractions). Parametric AR spectral estimation is commonly used to analyse the HRV signal association with the power spectrum bands related to simpatho-vagal activities. However, the computation is limited by a compromise between time resolution and stability. This study aims to indicate and to evaluate the performances of a multiple, recursive, time-varying AR identification of HRV power spectral density, which adapts to signal characteristic. This solution provides both synthetic information in stationary periods and accurate signal tracking during transients. An additional information, related to signal variation speed, can be used to provide a recognition of transient episodes. Test signals were used to measure the performance of the adaptive method with respect to the standard spectral estimation. Error analysis confirms the enhanced performances of the adaptive metho
Maradona e la Cina: tra passione e politica
No full textDiego Armando Maradona rappresenta agli occhi del
mondo occidentale un mito sportivo (Mitra, Naha, 2017;
Massarelli, Terret, 2011), ricco di sfumature e contraddizioni
che hanno reso l’uomo una leggenda. Maradona ha forse rap presentato il primo fenomeno veramente globale nel mondo
del calcio e dello sport in generale: il suo nome è giunto anche
negli angoli più remoti del globo, dopo la vittoria della Cop pa del Mondo del 1986 (Bavassi, Kaczer, Fernández, 2019;
Bifulco, Tirino, 2018; Bifulco, Dini, 2014; Hughson, Moore,
2012). Come hanno accuratamente descritto Goldblatt e Ac tonharac in The soccer book:
Si potrebbe quasi dire che il calcio è il linguaggio universale.
Se vi trovaste nel bel mezzo di un paese sconosciuto senza
conoscere la lingua locale, sareste comunque in grado di av viare una conversazione utilizzando alcuni gesti delle mani
accompagnati dai nomi di alcuni giocatori importanti. Met tete una mano all’altezza del petto mentre dite “Pelé” e poi
alzatela con la parola “Maradona”, e inizierete rapidamente a
fare amicizia (Goldblatt, Actonharac, 2018, p. 10)
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