BIM SYSTEM FOR THE CONSERVATION AND PRESERVATION OF THE MOSAICS OF SAN MARCO IN VENICE

The Basilica of San Marco in Venice is a well-known masterpiece of World Heritage. It is a real multi-faceted architecture. The management of the church and its construction site is very complicated, and requires an efficient system to collect and manage different kinds of data. The BIM approach appeared to be the most suitable to collect multi-source data, to monitor activities and guarantee the well-timed operations inside the church. The purpose of this research was to build a BIM of the Basilica, considering all aspects that characterize it and that require particular care.Many problems affected the phase of the acquisition of data, and forced the team to establish a clear working pipeline that allowed the survey simultaneously, hand in hand, with all the usual activities of the church. The fundamental principle for the organization of the whole work was the subdivision of the entire complex in smaller parts, which could be managed independently, both in the acquisition and the modelling stage. This subdivision also reflects the method used for the photogrammetric acquisition. The complexity of some elements, as capitals and statues, was acquired with different Level of Detail (LoD) using various photogrammetric acquisitions: from the most general ones to describe the space, to the most detailed one 1:1 scale renderings. In this way, different LoD point clouds correspond to different areas or details.As evident, this pipeline allows to work in a more efficient way during the survey stage, but it involves more difficulties in the modelling stage. Because of the complexity of the church and the presence of sculptural elements represented by a mesh, from the beginning the problem of the amount of data was evident: it is nonsense to manage all models in a single file.The challenging aspect of the research job was the precise requirement of the Procuratoria di San Marco: to obtain the 1:1 representation of all the mosaics of the Basilica. This requirement significantly increased the effort in the acquisition stage, because it was necessary to reach a submillimetre resolution in the photographic images sufficient to distinguish perfectly each single tessera, also in the highest domes (28 meters). Furthermore, it introduced a new problem about the management of the gigapixel - orthophotos.The BIM approach presented in this paper tries to offer a solution to all these problems. The BIM application is based not on commercial software, but on a self-implemented system, which was previously tested on the Main Spire of Milano Cathedral. The multi-scale and multi-area approach have also been maintained in the BIM construction phase.In the case of Basilica di San Marco, the most important requirement was the management of the orthophotos of each single element. It was necessary to give the user the possibility to recover, for each item, not only the geometric model, but also the raster representation -orthophoto- of its surface: in order to do it, the BIM model acts as a three-dimensional catalogue

Contribution of acoustic emission to the understanding of sulfide stress cracking of low alloy steels

cited By 17International audienceThe acoustic emission technique was applied to standard tests devoted to evaluate sulfide stress cracking susceptibility of steels for oil and gas industry. The mapping of the density of AE signals vs. their location on the specimen gauge length as a function of time allowed early detection of cracking, and gave meaningful information on incubation times and propagation rates. Sulfide stress cracking initiation was correlated with the presence of critical surface defects. A mechanism involving plastic strain and/or metal dissolution was proposed to account for crack propagation. © 2011 Elsevier Ltd

Hydrogen charging in low alloy steels exposed to H 2 S: impact of CO 2 or N 2 in the gas mixture

International audienceThis paper examines the influence of CO 2 / H 2 S ratio on hydrogen charging in low alloy steels. Hydrogen flux through the steel surface is the driving force for sulfide stress cracking (SSC). The impact of H 2 S and pH on SSC severity is extremely well documented, and these two parameters are used in the SSC severity diagram of ISO 15156-2 [1]. However, the CO 2 / H 2 S ratio is not considered in standard SSC testing procedures, even though it has a strong impact on corrosion. Indeed, according to several authors, competitive adsorption between HS-and HCO 3-on the steel surface could modify the charging flux, thus the SSC risks. The goal of the present study was to check if hydrogen charging is influenced by other parameters than the sole pH and P H2S. Experiments consisted in hydrogen permeation measurements through HSLA steel thin membranes. They were performed under cathodic charging in order to avoid corrosion products precipitation. Charging solutions with different H 2 S concentrations with or without CO 2 were used, in order to examine the individual contributions to the charging flux, and hence to evaluate a possible impact on SSC risks

Acoustic emission monitoring of wet H2S cracking of linepipe steels: Application to hydrogen-induced cracking and stress-oriented hydrogen-induced cracking

cited By 9International audienceAcoustic emission (AE) was used for monitoring steel cracking during exposure to wet hydrogen sulfide (H2S) environments. A method for filtering AE data related to hydrogen-induced cracking (HIC) was presented and applied for several case studies. In a series of tests on unstressed sweet service steels, evolution of AE indicated three successive HIC phases. An initial incubation period corresponded to hydrogen entry in the steel, during which no cracking occurred. Then two cracking phases were detected. The first was associated with decohesion of weak steel interphases. The second was identified as crack propagation under high internal hydrogen pressure. Crack propagation decreased and eventually ceased over time. Analysis of AE data was then used to evaluate the extent of HIC after sour exposure. Correlation was found when appropriate data filtering was applied. AE analysis was also applied to sour service steels under an applied load. The first steel exhibited HIC AE signals. Its fracture surface was typical of a stress-oriented hydrogen-induced cracking (SOHIC) mode of failure, in good agreement with AE results. For the second steel, which also failed during the test, no AE related to HIC was detected. Fracture surface was typical of sulfide stress cracking (SSC), also in good agreement with AE findings. © 2011, NACE International

Improving pH Prediction for High Pressure and High Temperature Applications in Oil and Gas Production

International audiencepH prediction represents a crucial step before selecting materials for use in sour oil and gas wells as regards weight loss corrosion and H 2 S cracking. Among the numerous parameters which determine the equilibrium pH, important ones are CO 2 and H 2 S partial pressures (P CO2 and P H2S respectively), the total pressure, the ionic strength and the chemical composition of the solution, and the temperature. Most models used by oil and gas operators present a too narrow range of validity for these parameters, which makes them inappropriate for high pressure and high temperature (HPHT) fields or for CO 2 reinjection. This paper presents modeling improvements which allows extending the prediction validity in temperature and pressure to respectively 200 °C and 1,000 bar of total pressure, and for an ionic strength up to 5 mol.kg-1. These improvements take into account the fugacities in gas phase of CO 2 and H 2 S as determined by the Soreide and Whitson formalism. The influence of water and CH 4 pressure is also taken into account up to several hundred bars. Activity coefficients in the water phase are calculated using the Pitzer model. The consistency of the model is verified by comparison with experimental measurements of pH under high pressure. It is then applied to oil and gas applications at high pressure and high temperature. The impact of the new calculation method is discussed both for pH evaluation and also for H 2 S activity, with strong implications for the evaluation of SSC risks

pH prediction in concentrated aqueous solutions under high pressure of acid gases and high temperature

International audienceAn extended model for pH prediction in oil and gas environments has been developed. Accurate pH calculations for high pressure and high temperature applications depends mainly on CO2 and H2S partial pressures, the ionic strength, the chemical composition of the solution, and the temperature. Accounting for the non-ideal behaviors of liquid and gas phases allows pH calculations up to 200 °C, 2000 bar total pressure, and ionic strengths up to 5 mol.L-1. The results are consistent with experimental measurements and with other models reported in the literature

Applications of action CAM sensors in the archaeological Yard

In recent years, special digital cameras called "action camera" or "action cam", have become popular due to their low price, smallness, lightness, strength and capacity to make videos and photos even in extreme environment surrounding condition. Indeed, these particular cameras have been designed mainly to capture sport actions and work even in case of dirt, bumps, or underwater and at different external temperatures. High resolution of Digital single-lens reflex (DSLR) cameras are usually preferred to be employed in photogrammetric field. Indeed, beyond the sensor resolution, the combination of such cameras with fixed lens with low distortion are preferred to perform accurate 3D measurements; at the contrary, action cameras have small and wide-angle lens, with a lower performance in terms of sensor resolution, lens quality and distortions. However, by considering the characteristics of the action cameras to acquire under conditions that may result difficult for standard DSLR cameras and because of their lower price, these could be taken into consideration as a possible and interesting approach during archaeological excavation activities to document the state of the places. In this paper, the influence of lens radial distortion and chromatic aberration on this type of cameras in self-calibration mode and an evaluation of their application in the field of Cultural Heritage will be investigated and discussed. Using a suitable technique, it has been possible to improve the accuracy of the 3D model obtained by action cam images. Case studies show the quality and the utility of the use of this type of sensor in the survey of archaeological artefacts

Apoptosis gene expression profiling in lens development

During lens development, epithelial cells located at the equatorial region of the lens undergo terminal differentiation to form fibre cells resulting in cell elongation and degradation of all intracellular organelles. Failure to complete this process successfully can result in cataract. This process is thought to be an attenuated form of classical apoptosis. This study was completed to give a comprehensive analysis of apoptosis genes in the developing mouse lens. Macroarrays containing 243 immobilised cDNAs with a known role in apoptosis were utilised to examine the gene expression at different developmental stages. The stages examined were postnatal day 7 and postnatal day 14. Over 100 apoptosis genes were shown to be expressed above background with 20 genes demonstrating significantly differential expression (2-fold or greater change in expression, p-value < 0.05), with highest expression at PI4. PCR confirmed expression of all the genes identified from the array results, and differential expression was confirmed for 52% of the genes. Protein expression of two selected genes, axl and mcl-1, was demonstrated using western blotting. Lens morphology was examined in transgenic mice generated to contain an extended CAG repeat in the huntingtin gene (one of the genes identified from the arrays). Morphology was compared between homozygote, heterozygote and wild-type mice. The presence of the mutated gene did not affect denucleation during lens differentiation and no statistically significant difference was seen in the dimensions of the organelle free zone (OFZ) of the wild-type and homozygote mice. A cross-species comparison was completed. Gene expression of the genes shown to be highly expressed and differentially expressed from the array results was examined in embryonic chick lenses. From the results of this part of the study expression was seen for 83% of genes. These results add to the argument that the process of differentiation is similar in both mouse and chick lenses.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Interventions in urban geopolitics

© 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0

Metabolic investigations prevent liver transplantation in two young children with citrullinemia type I

Acute liver failure may be caused by a variety of disorders including inborn errors of metabolism. In those cases, rapid metabolic investigations and adequate treatment may avoid the need for liver transplantation. We report two patients who presented with acute liver failure and were referred to our center for liver transplantation work-up. Urgent metabolic investigations revealed citrullinemia type I. Treatment for citrullinemia type I avoided the need for liver transplantation. Acute liver failure as a presentation of citrullinemia type I has not previously been reported in young children. Although acute liver failure has occasionally been described in other urea cycle disorders, these disorders may be underestimated as a cause. Timely diagnosis and treatment of these disorders may avoid liver transplantation and improve clinical outcome. Therefore, urea cycle disorders should be included in the differential diagnosis in young children presenting with acute liver failure