1,354,678 research outputs found
A Critical Review and Commentary on Cerveri’s ‘popular’ Compositions (BdT 434), with Particular Attention to Relations with Arabic Poetry
No full textreservedLa ricerca si concentra sul trovatore Cerveri ‘de Girona’ (BdT 434) fornendo un’edizione di otto
componimenti, in lingua d’oc, di stampo popolareggiante. Inoltre, lo studio esplora i legami con la poesia arabo-
andalusa in 'Attraversamenti', confrontando motivi e immagini con, per esempio, Ibn Quzmān e Ibn Hamdīs.
L’obiettivo è chiarire la posizione letteraria unica di Cerveri e le prime relazioni liriche tra occitano e arabo.This research focuses on troubadour Cerveri ‘de Girona’ (BdT 434) as a bridge between fading Occitan
lyric and emerging Catalan literature. It provides an analysis of eight ‘popular’ works, using manuscript
evidence, especially from Sg, it reconstructs his poetic voice, blending Provençal and Catalan. The study
explores links to Arabic-Andalusian poetry, particularly in 'Attreversamenti' comparing motifs and imagery for
example with Ibn Quzmān and Ibn Hamdīs. It aims to clarify Cerveri’s unique literary position and early
Occitan-Arabic lyrical relations
Calibrating a video camera pair with a rigid bar
No full textIn this paper a new procedure to determine all the geometrical parameters of a stereo-system is presented. It is based on
surveying a rigid bar carrying two markers on its extremities moved inside the working volume and it does not require
grids or complex calibration structures. The external parameters are estimated through the epipolar geometry up to
a scale factor which is determined from the true length of the bar. The focal lengths are determined using the properties
of the absolute conic in the projective space. The principal points are computed through a non-linear minimisation
carried out through an evolutionary optimisation. The accuracy of the method is assessed on real data and it compares
favourably with that obtained through classical approaches based on control points of known 3D coordinates
Generi poetici di Cerveri de Girona
No full textAccanto ad esempi singoli di virtuosismo e sperimentalismo formale, l'opera del trovatore duecentesco Cerveri de Girona si caratterizza sul versante metrico per due gruppi principali di testi, quelli in forme da ballo (dança, balada) e quelli ascritti alla categoria del "vers". La natura di quest'ultima tipologia si rivela di particolare interesse per seguire l'evoluzione della lirica trobadorica dal 12 secolo sino all'ultimo scorcio del 13.Next to examples of individual virtuosity and formal experimentalism, the work of Catalan troubadour Cerveri de Girona (late thirteenth-century) is characterized, from the point of view of metrics, by two main groups of texts, those in form of dance-songs (dança, balada) and those ascribed to the category of the "vers". The nature of the latter type is of particular interest to follow the evolution of the troubadour lyric from the 12th century until the last glimpse of the 13
Predicting Knee Joint Instability Using a Tibio-Femoral Statistical Shape Model
No full textStatistical shape models (SSMs) are a well established computational technique to represent the morphological variability spread in a set of matching surfaces by means of compact descriptive quantities, traditionally called “modes of variation” (MoVs). SSMs of bony surfaces have been proposed in biomechanics and orthopedic clinics to investigate the relation between bone shape and joint biomechanics. In this work, an SSM of the tibio-femoral joint has been developed to elucidate the relation between MoVs and bone angular deformities causing knee instability. The SSM was built using 99 bony shapes (distal femur and proximal tibia surfaces obtained from segmented CT scans) of osteoarthritic patients. Hip-knee-ankle (HKA) angle, femoral varus-valgus (FVV) angle, internal-external femoral rotation (IER), tibial varus-valgus (TVV) angles, and tibial slope (TS) were available across the patient set. Discriminant analysis (DA) and logistic regression (LR) classifiers were adopted to underline specific MoVs accounting for knee instability. First, it was found that thirty-four MoVs were enough to describe 95% of the shape variability in the dataset. The most relevant MoVs were the one encoding the height of the femoral and tibial shafts (MoV #2) and the one representing variations of the axial section of the femoral shaft and its bending in the frontal plane (MoV #5). Second, using quadratic DA, the sensitivity results of the classification were very accurate, being all >0.85 (HKA: 0.96, FVV: 0.99, IER: 0.88, TVV: 1, TS: 0.87). The results of the LR classifier were mostly in agreement with DA, confirming statistical significance for MoV #2 (p = 0.02) in correspondence to IER and MoV #5 in correspondence to HKA (p = 0.0001), FVV (p = 0.001), and TS (p = 0.02). We can argue that the SSM successfully identified specific MoVs encoding ranges of alignment variability between distal femur and proximal tibia. This discloses the opportunity to use the SSM to predict potential misalignment in the knee for a new patient by processing the bone shapes, removing the need for measuring clinical landmarks as the rotation centers and mechanical axes
Pair-wise vs group-wise registration in statistical shape model construction: representation of physiological and pathological variability of bony surface morphology
No full textStatistical shape models (SSM) of bony surfaces have been widely proposed in orthopedics, especially for anatomical bone modeling, joint kinematic analysis, staging of morphological abnormality, and pre- and intra-operative shape reconstruction. In the SSM computation, reference shape selection, shape registration and point correspondence computation are fundamental aspects determining the quality (generality, specificity and compactness) of the SSM. Such procedures can be made critical by the presence of large morphological dissimilarities within the surfaces, not only because of anthropometrical variability but also mainly due to pathological abnormalities. In this work, we proposed a SW pipeline for SSM construction based on pair-wise (PW) shape registration, which requires the a-priori selection of the reference shape, and on a custom iterative point correspondence algorithm. We addressed large morphological deformations in five different bony surface sets, namely proximal femur, distal femur, patella, proximal fibula and proximal tibia, extracted from a retrospective patient dataset. The technique was compared to a method from the literature, based on group-wise (GW) shape registration. As a main finding, the proposed technique provided generalization and specificity median errors, for all the five bony regions, lower than 2mm. The comparative analysis provided basically similar results. Particularly, for the distal femur that was the shape affected by the largest pathological deformations, the differences in generalization, specificity and compactness were lower than 0.5mm, 0.5mm, and 1%, respectively. We can argue the proposed pipeline, along with the robust correspondence algorithm, is able to compute high-quality SSM of bony shapes, even affected by large morphological variability
Complete calibration of a stereo photogrammetric system through control points of unknown coordinates
No full textLocal shape similarity and mean-shift curvature for deformable surface mapping of anatomical structures
No full textThis paper reports a novel method for deformable registration of digital anatomical surfaces. The method capitalizes upon the iterative local affine iterative closest point (ICP) approach that applies an affine transformation per surface vertex along with a regularization constraint to force neighboring surface vertices to undergo similar transformations. More robust vertex correspondence with respect to simple closest point was obtained by exploiting local shape similarity metrics, which includes vertex distance, surface normal, and local curvature. The local curvature was mean shifted at run-time, during the iterative optimization, to make the point correspondence process less dependent upon the surface noise and resolution. The experimental validation was performed on three surface datasets (femur, hemi-pelvic bone, and liver). The registration results showed that the proposed method outperforms, across all the three surface datasets (rmse: 0.19 mm, 0.30mm, 0.61 mm), global affine ICP (rmse: 2.89mm, 3.95mm, and 8.30 mm), local affine ICP (rmse: 0.31 mm, 1.61 mm, and 1.63 mm) and coherent point drift (rmse: 1.99 mm, 2.39 mm, and 4.78 mm) methods. As a whole, the mean-shifted curvature increased the registration accuracy by about 20%
Representative 3D shape of the distal femur, modes of variation and relationship with abnormality of the trochlear region
No full textThe anatomy of the distal femur has a predominant influence on the mechanics of both patello- and tibio-femoral joints. Especially, the morphological degeneration of the trochlear region dramatically affects the overall knee biomechanics and, from a clinical point of view, the staging of such a degeneration is fundamental to tailor the optimal therapeutic solution. The description of morphological variability and pathological inter-subject differences of the trochlea can be achieved by means of statistical shape modeling of a set of three-dimensional surfaces. This representation encodes information, spread into the dataset, in terms of modes of variations that model global, regional and even local morphological features. In view of that, the aim of this study was to develop a statistical shape model of the distal femur to capture the variability of the trochlear region into specific modes of variation and to study the interplay between the variation of the trochlea and the condylar regions. Using CT scans of patients affected by different levels of abnormality of the trochlear region, the distal femur geometries were co-registered to a reference shape using the pair-wise correspondence approach and principal component analysis provided the key modes of variation (MoVs). Apart from the first two MoVs, which described the global magnitude of the femur and the shaft length, the main following ones showed high correlation with sulcus depth (r(2) = 0.70), sulcus angle (r(2) = 0.70), lateral trochlear inclination (r(2) = 0.66), and height of the two condylar facets in the anterior direction (r(2) = 0.66), whose abnormal variations are typical signs of trochlear degeneration. High interplay between trochlear abnormalities and notch width (r(2) = 0.71), lateral condylar size (r(2) = 0.67), and medial condylar size (r(2) = 0.99) was found. Interestingly, the model predicted morphological associations not included in the training dataset, nonetheless difficult to demonstrate physiologically. Interestingly from a biomechanical point of view, the distribution of some MoVs was found statistically different across the patients featuring physiological and pathological ranges of hip-knee-ankle alignment, femoral internal-external rotation and tibial slope. However, no linear correlation was found between the angular indexes and such MoVs. As a result, we can assert that statistical modeling of the distal femur are to date an effective way to visualize and quantify abnormalities of the trochlear regions supporting the introduction of advanced analysis, diagnostic and treatment support tools to elucidate physiologic and pathological variability in the morphology, to drive the staging and assist the selection of the optimal treatment option tailored to the patient. (C) 2019 Elsevier Ltd. All rights reserved
Evolution strategies and epipolar geometry for dynamic calibration of a photogrammetric camera system
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