87,867 research outputs found
Market and Non-Market Mechanisms for the Optimal Allocation of Scarce Resources
No full textBoth market (e.g. auctions) and non-market mechanisms (e.g. lotteries and priority lists) are used to allocate a large amount of scarce public resources that produce large private benefits and small consumption externalities. I study a model in which the use of both market and non-market mechanisms can be rationalized. Agents are risk neutral and heterogeneous in terms of their monetary value for a good and their opportunity cost of money, which are both private information. The designer wants to allocate a set of identical goods to the agents with the highest values. To achieve her goal, she can screen agents on the basis of their observable characteristics, and on the basis of information on their willingness to pay that she can extract using market mechanisms. In contrast to models where willingness to pay and value coincide, a first best cannot be achieved. My main result is that both market and non-market mechanisms, or hybrid mechanisms, can be optimal depending on the prior information available to the designer. In particular, non-market mechanisms may be optimal if the value is positively correlated with the opportunity cost of money.
CULTURAL HERITAGE RECONSTRUCTION FROM HISTORICAL PHOTOGRAPHS AND VIDEOS
No full textHistorical archives save invaluable treasures and play a critical role in the conservation of Cultural Heritage. Old photographs and videos, which have survived over time and stored in these archives, preserve traces of architecture and urban transformation and, in many cases, are the only evidence of buildings that no longer exist. They are a precious source of enormous informative potential in Cultural Heritage documentation and save invaluable treasures. Thanks to photogrammetric techniques it is possible to extract metric information from these sources useful for 3D virtual reconstructions of monuments and historic buildings. This paper explores the ways to search for, classify and group historical data by considering their possible use in metric documentation and aims to provide an overview of criticality and open issues of the methodologies that could be used to process these data. A practical example is described and presented as a case study. The video “Torino 1928”, an old movie dating from the 1930s, was processed for reconstructing the temporary pavilions of the “Exposition” held in Turin in 1928. Despite the initial concerns relating to processing this kind of data, the experimental methodology used in this research has allowed to reach a quality of results of acceptable standard
Una memoria apuleiana in Sidonio Apollinare: tra stile epistolare e modelli retorici
No full textIn the Letter 9, 2 Sidonius Apollinaris declines Euphronius’ request to compose a work of biblical exegesis; even though it is short, the epistle
has a high degree of rhetorical elaboration. The paper focuses the recusatio’s topics, particularly the one in which Sidonius compares himself with the preceding exegetes (Origenes, Hieronimus, Augustinus). The author uses two images for comparison: the second one presents the motif of bird singing and shows evidence of the influence of a passage of the Apuleius’ Florida
BENCHMARK OF METRIC QUALITY ASSESSMENT IN PHOTOGRAMMETRIC RECONSTRUCTION FOR HISTORICAL FILM FOOTAGE
No full textQuality assessment in photogrammetric processing is fundamental to obtain metric information and to reconstruct 3D models of Cultural Heritage, especially when it has been lost or changed over time. The determination of metric precision is technically challenging when dealing with historical films and videos that in many cases represent the only remaining traces of this heritage, which is useful for architectural, archaeological and restoration studies. This paper examines the suitability of existing photogrammetric software to evaluate the maximum possible metric accuracy for processing videos shot with fixed camera motions. In order to evaluate the metric quality obtained processing historical film footage with photogrammetric techniques, a benchmark was created on a new video dataset with the aim of reproducing the camera motions in which old video were shot. Three different camera motions were considered: Up/Down Motion-Tilting, Left/Right Motion-Trucking and Rolling Motion-Panning. The methodology was experimented on Valentino Castle in Turin, a monument inscribed in the UNESCO World Heritage List. Data were processed with the implementation of open source Structure-from-Motion algorithms and the results were analysed for the evaluation of metric quality. Results show the different maximum precision assessments according to the different typologies of camera motion. This research provides fundamental support to historical studies on Cultural Heritage, creating a sharing standard with zero-cost data and tools useful for both geomatics and restorers
Comparative Evaluation of NeRF Algorithms on Single Image Dataset for 3D Reconstruction
No full textThe reconstruction of three-dimensional scenes from a single image represents a significant challenge in computer vision, particularly in the context of cultural heritage digitisation, where datasets may be limited or of poor quality. This paper addresses this challenge by conducting a study of the latest and most advanced algorithms for single-image 3D reconstruction, with a focus on applications in cultural heritage conservation. Exploiting different single-image datasets, the research evaluates the strengths and limitations of various artificial intelligence-based algorithms, in particular Neural Radiance Fields (NeRF), in reconstructing detailed 3D models from limited visual data. The study includes experiments on scenarios such as inaccessible or non-existent heritage sites, where traditional photogrammetric methods fail. The results demonstrate the effectiveness of NeRF-based approaches in producing accurate, high-resolution reconstructions suitable for visualisation and metric analysis. The results contribute to advancing the understanding of NeRF-based approaches in handling single-image inputs and offer insights for real-world applications such as object location and immersive content generation
Antiphosphotyrosine immunoprecipitation of an insulin-stimulated receptor phosphatase activity from FRTL5 cells
No full textRelation of various plasma growth factor levels in patients with stable angina pectoris and total occlusion of a coronary artery to the degree of coronary collaterals
No full textWe assessed (1) angiogenic factors in patients with stable angina and longstanding (> or =24 months) total occlusion of a single coronary artery and (2) the relation between plasma levels of angiogenic factors and the development of collateral vessels as evaluated by coronary angiography. Plasma concentrations of vascular endothelial growth factor (VEGF(165)), fibroblast growth factor, placenta-derived growth factors (PlGFs), and hepatocyte growth factor were assessed in 96 patients with stable angina and longstanding (> or =24 months) total occlusion of a single coronary artery. According to coronary angiographic results, 18 patients had no visible collaterals (group 0), 21 patients had visible collaterals but no filling of the recipient epicardial vessel (group 1), and 57 patients showed filling (partial or complete) of the recipient epicardial vessel by collaterals (group 2). Plasma VEGF(165) and PlGF concentrations were higher in group 1 than in groups 0 and 2 (VEGF(165) 75 pg/ml, range 24 to 105, vs 23 pg/ml, range 15 to 29, and 19 pg/ml, range 10 to 41, respectively, F = 5.53, p = 0.006; PlGF 35 pg/ml, range 3.5 to 105, vs 1 pg/ml, range 1 to 38, and 1 pg/ml, range 1 to 5, respectively, F = 7.09, p = 0.008). Plasma VEGF(165) and PlGF levels were similar in groups 0 and 2. There was no significant difference in plasma levels of fibroblast and hepatocyte growth factor concentrations across the 3 groups. In conclusion, plasma levels of angiogenic growth factors differ among patients with stable angina pectoris and longstanding total coronary occlusion
A MATCH-MOVING METHOD COMBINING AI AND SFM ALGORITHMS IN HISTORICAL FILM FOOTAGE
No full textSearching for suitable material for photogrammetry is a key part in the documentation of Cultural Heritage. Photogrammetry can be used to produce a metrically certified 3D model. Material contained in historical film footage archives is especially useful for documentation when the heritage has been lost. In this research an innovative match-moving method is proposed that aims to exploit Artificial Intelligence and SfM algorithms to identify the frames extracted from a film footage in which the lost monument appears and that are suitable to be processed with photogrammetry for its 3D reconstruction. First of all the identification and tracking of the heritage in the videos was performed training an object detection Neural Network. Then the frames detected were automatically extracted with the coordinates of the bounding boxes that contain the monument. The camera motions were identified by selecting only the shots taken from multiple points of view of the same scene and analysing the evolution of the bounding boxes position over time. A further check of the material was necessary to select only sequences and to eliminate single frames and images from different historic periods. After this process, only the correct frames were automatically selected and processed with photogrammetry and the quality of the obtained 3D model was assessed. The method experimented in this research represents a powerful tool in the field of Cultural Heritage because it makes the selection of suitable material for photogrammetry automatic. Moreover it offers important insights that could be extended to other sectors
A first proposal of an algorithm for the evaluation of the error in the photogrammetric restitution
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