1,721,165 research outputs found
Retopology and Simplification of Reality-based Models for Finite Element Analysis
No full textReality-based 3D techniques and Finite Element Analysis share the way the object under investigation is discretized. Although their purpose, the generation methods and the quality metrics are dierent, both of them ground on the concept of mesh. Unfortunately, a mesh derived from a reality-based technique are not suitable to be used in a nite element solver directly. This paper aims at comparing dierent methods to prepare computational mesh of geometries derived from non-contact reality-based technologies. A benchmark test object has been acquired with dierent devices, a triangulation laser scanner, a multi-stripe triangulation scanner and a digital camera, and post processed in order to x artifacts. Then, two dierent decimation approaches have been used: a triangular simplication and retopology. The acquired geometry, before and after the simplications, has been compared with a CAD model employed as reference: mean and standard deviation between the nominal and the acquired geometries have been tracked. Finally, a tensile test has been simulated making use of a general-purpose nite element analysis software and the results have been compared with the exact solution
3D Modelling from Real Data
Full text linkThe genesis of a 3D model has basically two definitely different paths. Firstly we can consider the CAD generated models, where the shape is defined according to a user drawing action, operating with different mathematical “bricks” like B-Splines, NURBS or subdivision surfaces (mathematical CAD modelling), or directly drawing small polygonal planar facets in space, approximating with them complex free form shapes (polygonal CAD modelling). This approach can be used for both ideal elements (a project, a fantasy shape in the mind of a designer, a 3D cartoon, etc.) or for real objects. In the latter case the object has to be first surveyed in order to generate a drawing coherent with the real stuff. If the surveying process is not only a rough acquisition of simple distances with a substantial amount of manual drawing, a scene can be modelled in 3D by capturing with a digital instrument many points of its geometrical features and connecting them by polygons to produce a 3D result similar to a polygonal CAD model, with the difference that the shape generated is in this case an accurate 3D acquisition of a real object (reality-based polygonal modelling).
Considering only device operating on the ground, 3D capturing techniques for the generation of reality-based 3D models may span from passive sensors and image data (Remondino and El-Hakim, 2006), optical active sensors and range data (Blais, 2004; Shan & Toth, 2008; Vosselman and Maas, 2010), classical surveying (e.g. total stations or Global Navigation Satellite System - GNSS), 2D maps (Yin et al., 2009) or an integration of the aforementioned methods (Stumpfel et al., 2003; Guidi et al., 2003; Beraldin, 2004; Stamos et al., 2008; Guidi et al., 2009a; Remondino et al., 2009; Callieri et al., 2011). The choice depends on the required resolution and accuracy, object dimensions, location constraints, instrument’s portability and usability, surface characteristics, working team experience, project’s budget, final goal, etc.
Although aware of the potentialities of the image-based approach and its recent developments in automated and dense image matching for non-expert the easy usability and reliability of optical active sensors in acquiring 3D data is generally a good motivation to decline image-based approaches. Moreover the great advantage of active sensors is the fact that they deliver immediately dense and detailed 3D point clouds, whose coordinate are metrically defined. On the other hand image data require some processing and a mathematical formulation to transform the two-dimensional image measurements into metric three-dimensional coordinates. Image-based modelling techniques (mainly photogrammetry and computer vision) are generally preferred in cases of monuments or architectures with regular geometric shapes, low budget projects, good experience of the working team, time or location constraints for the data acquisition and processing.
This chapter is intended as an updated review of reality-based 3D modelling in terrestrial applications, with the different categories of 3D sensing devices and the related data processing pipelines
Consolidation of Carrara Marble by Hydroxyapatite and Behaviour After Thermal Ageing
No full textIn this study, the use of hydroxyapatite (HAP), recently proposed for limestone consolidation, was investigated on unweathered and artificially weathered Carrara marble and the behaviour of HAP-treated samples towards thermal weathering was evaluated, by means of an accelerated thermal weathering test. The results of the study indicate that HAP is a very promising consolidant for marble, able to significantly improve mechanical properties without substantially altering pore size distribution and to provide some mitigation against thermal weathering
Farmhouses in the Phlegrean Fields between archaeology and architectural palimpsest. A multi-disciplinary approach
No full textThe contribution aims to deepen the study of the rural architectures in
Campi Flegrei, with particular reference to the territorial area of Pozzuoli. Country
houses, manor houses in the countryside, agricultural and lookout towers, rural
outbuildings, farms born on archaeological remains, are the components of a rich
architectural heritage strewn over agricultural land of Campi Flegrei; a heritage not
yet fully known and cataloged, which pours in a state of apparent abandonment and
constitutes an irreproducible repertoire of building traditions, materials and local
techniques of undeniable interest. The study, which uses the results of a research,
started by a group of scholars of the “Federico II” and funded by Regione
Campania for the biennium 2004–2006, is characterized by an interdisciplinary
approach, and will address (1) the relationship with the landscape of these settlements,
(2) the reuse of ancient and existing buildings highlighting the continuity of
use, (3) the technical-constructive and typological aspects and more specifically the
architectural and materials ones. Two illustrative case-studies will be chosen,
detailed through a careful graphic and stratigraphic relief, as well as through
diagnostic surveys: the first one, relative to the area of Via Campana, which consists
of a farm built on Roman remains witnessed by the presence of a nymphaeum in
opus reticolatum, and the second one related to a home-farm, with a more complex
plant, arose ex novo in the eighteenth century for the production of wine. In both
cases will be highlighted the recurring conservative critical and the mechanisms of
degradation and damage, aimed to the detection of correct methods for the conservation
of this ‘fragile’ heritage
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
Recovery and Reuse of the Architectural and Urban Heritage of Carbonia, a 20th-Century Company Town. Materials for a Handbook
No full textThe policies and strategies put in place in 2001 for the requalification of the architectural heritage of the company town of Carbonia, and for the recovery of the “Great Mine of Serbariu” (that won the Landscape Award of the Council of Europe in 2010-2011), was based on a close collaboration between the University of Cagliari and the municipal administration of Carbonia.“The Handbook for the recovery” whose construction is still underway, fits this framework and coincides with an operational tool that regulates the action on the built heritage. It does not provide a catalogue of standardized solutions, but merely defines a knowledge base to guide the designers towards the recognition of the buildings’ invariant aspects and towards the understanding of the original architectural expression
A multidisciplinary approach for the assessment of great historical structures: Ties of “Duomo di Milano”
No full textAn investigation methodology, based on a scientific approach for historical structures, has been applied to the case study of the Duomo di Milano. In particular, a continuous process of data acquisition, analysis of structural behaviour, diagnosis and safety evaluation is followed with the aim of assessing metallic ties present in the Cathedral. Different techniques and fields of expertise were used for data acquisition: historical investigation gave important information on the ties origin, their structural purpose and the construction process of the Cathedral; the wide experimental campaign included visual inspection, material characterization, and dynamic tests on the original ties and contributed to the understanding of the structural system. The main results and considerations from such a multidisciplinary investigation are presented in the paper, providing a reference from a real case-study. Relevant aspects for the study of the Cathedral’s structural behaviour are addressed, various approaches to be used are proposed, such as limit analysis or Finite Element Modelling (FEM) and their benefits are outlined. These models, once validated through the prediction of past and present states of the structure, will be used during diagnosis and safety evaluation to predict the future behaviour, or identify potential causes of eventual observed damage, as well as to evaluate the current state of the stress in ties measured with a more refined Non-destructive testing (NDT) approach
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
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