Abstract After decades of operation in nuclear power plants, Once-Through Steam Generators (OTSGs) were recently proposed for nuclear fusion applications. In particular, they are supposed to be installed in the primary cooling systems of the European Union Demonstration fusion power plant (EU-DEMO). One of the key reactor components is the Breeding blanket (BB). Among the BB concepts that are currently under study, Water-Cooled Lithium-Lead (WCLL) option was considered for this work. The WCLL blanket is divided in two main subsystems, the breeder zone (BZ) and the first wall (FW), each one provided with an independent cooling circuit, named Primary Heat Transfer System (PHTS). Thermal power removed from BB by BZ and FW PHTS is driven to the Power Conversion System (PCS) to be converted into electricity. The thermal coupling is ensured by two OTSGs per system. At the Department of Astronautical, Electrical and Energy Engineering (DIAEE) of Sapienza University of Rome, a simulation activity was carried out to understand the component thermal-hydraulic behavior during DEMO normal operations. For calculation purposes, a full model of the steam generator was prepared by using a modified version of RELAP5/MOD3.3 system code. The computational activity performed allows to preliminary characterize the OTSG thermal-hydraulic performances during both pulse and dwell phases.
Abstract In fusion reactor blanket design, liquid metals are attractive working fluids since it is possible to combine in a single fluid the functions of coolant, tritium carrier and breeder. These electrically conductive fluids flow in the presence of a strong magnetic field, inducing the appearance of Lorentz forces and magnetohydrodynamic MHD effects. Increased pressure loss, particularly in complex geometry elements, is a critical point for blanket design. The MHD flow through an orifice plate made by electroconductive walls (c = 0.01 ÷ 0.1) has been analysed in this paper using ANSYS CFX in the range Re = 108, and Ha = 0 ÷ 300. A wide recirculation region is detected after the flow exits the orifice, with potentially harmful consequences for efficient tritium removal. Large pressure loss occurs in the orifice due to conductive wall and non-negligible axial length. The 3D pressure drop term is characterized through a local resistance coefficient (k) that is found to be k ≈ 0.205 for well conducting walls (c = 0.1) and k ≈ 0.063 for poorly conducting ones (c = 0.01).
Two metallurgical traditions coexisted in the Chalcolithic Southern Levant: the lost wax casting of polymetallic alloys and the pure copper technology. Details of their operational sequences are still unknown. To date, no production sites of lost wax casting technology have been found. Only the main steps of the pure copper technology can be reconstructed from the archaeological record. Therefore, an archaeological experiment was carried out to shed new light on both technologies. Concerning the pure copper technology, the experiment focussed on the draught technique and high-temperature behaviour of the crucible and furnace clays. Based on archaeological evidence, a furnace and crucibles were reconstructed with local clays used by ancient metallurgists. Instead of the commonly hypothesised blowpipes, bellows were used to produce the draught. The furnace was successfully operated with bellows and reached temperatures high enough to melt copper. Furthermore, the clays’ behaviour varied considerably due to high heat exposure, but they are suitable if used appropriately. Our experiment establishes this draught technique as a viable alternative to the commonly assumed blowpipes as well as the suitability of local clays.
Abstract In this paper we investigated the calculation of the anodic limit of two anions of ionic liquids, largely used as electrolyte of lithium batteries. Starting from a model based on calculations performed on single ions at the MP2 level of theory, we showed that the matching between calculation and experiments decreases while using more expanded basis set with respect to 6-31G**, possibly because of the destabilization of the neutral species when larger basis sets are considered. Additionally, in order to decrease the computational time, the performances for the calculation of the anodic limit obtained by means of a series of DFT functionals with increasing level of complexity (from the Generalized Gradient Approximation to the Range Separated Hybrid meta-Generalized Gradient Approximation) were compared. Overall, the best performing functionals are BMK, ωB97M-V and MN12-SX, while acceptable results can be obtained by M06-2X, M11, M08-HX and M11-L. Some less computationally expensive functionals, like CAM-B3LYP and ωB97X-D, also provide reasonable values of the anodic limit.
In the American West, wildfires and earthquakes are increasingly threatening the archaeological, historical, and tribal resources that define the collective identity and connection with the past for millions of Americans. The loss of said resources diminishes societal understanding of the role cultural heritage plays in shaping our present and future. This paper examines the viability of employing stationary and SLAM-based terrestrial laser scanning, close-range photogrammetry, automated surface change detection, GIS, and WebGL visualization techniques to enhance the preservation of cultural resources in California. Our datafication approach combines multi-temporal remote sensing monitoring of historic features with legacy data and collaborative visualization to document and evaluate how environmental threats affect built heritage. We tested our methodology in response to recent environmental threats from wildfire and earthquakes at Bodie, an iconic Gold Rush-era boom town located on the California and Nevada border. Our multi-scale results show that the proposed approach effectively integrates highly accurate 3D snapshots of Bodie’s historic buildings before/after disturbance, or post-restoration, with surface change detection and online collaborative visualization of 3D geospatial data to monitor and preserve important cultural resources at the site. This study concludes that the proposed workflow enhances the monitoring of at-risk California’s cultural heritage and makes a call to action to employ remote sensing as a pathway to advanced planning.
Abstract The Rongorongo is a system of writing, still undeciphered, from Easter Island in the Pacific. It consists of a corpus of twenty-six inscriptions, scattered around the world. This article presents the state-of-the art in the study of one of these inscriptions, Text D or the ‘Échancrée’ tablet housed in a museum in Rome, Italy. Through an integrated methodology based on photogrammetry and high-precision structured light scanning, a 3D model of the inscriptions is made available through a public 3D Viewer for the first time. The technique made use of the benefits of both methods of image acquisition: a very accurate, precise, high resolution, and metric reconstruction of the tablet geometry gained through the scanning process, and a high-quality texture achieved through photogrammetry. In addition, we present a new analysis of the text, through a close palaeographic examination of its signs, and corrections of previous hand drawings and transcriptions. The ultimate aim is to reach unbiased ‘readings’ of the signs through an integrated synergy of traditional palaeographic analysis and an advanced 3D model. These, applied to all the inscriptions, constitute the necessary stepping-stones for any decipherment attempt.
Despite the recent great success of the sequence-to-sequence paradigm in Natural Language Processing, the majority of current studies in Semantic Role Labeling (SRL) still frame the problem as a sequence labeling task. In this paper we go against the flow and propose GSRL (Generating Senses and RoLes), the first sequence-to-sequence model for end-to-end SRL. Our approach benefits from recently-proposed decoder-side pretraining techniques to generate both sense and role labels for all the predicates in an input sentence at once, in an end-to-end fashion. Evaluated on standard gold benchmarks, GSRL achieves state-of-the-art results in both dependency- and span-based English SRL, proving empirically that our simple generation-based model can learn to produce complex predicate-argument structures. Finally, we propose a framework for evaluating the robustness of an SRL model in a variety of synthetic low-resource scenarios which can aid human annotators in the creation of better, more diverse, and more challenging gold datasets. We release GSRL at github.com/SapienzaNLP/gsrl.
The high artistic and cultural relevance of particular objects, in this case from the Nuragic civilization, have stimulated the growth of a forgery industry, replicating small bronze boats (navicelle), statues (bronzetti), and other objects. It is often the case where the forgeries are of such quality that it becomes difficult to distinguish them from authentic artifacts without a proper chemical analysis. In this research, a Monte Carlo simulation algorithm for X-ray interactions with matter is used to obtain the chemical composition from the bulk of each object from a set of five. The method employed has the advantage of being completely nondestructive and relatively fast. The objects’ chemical composition and morphology were compared with the data available from authentic artifacts so their authenticity could be inferred. Four of the five objects are likely to be authentic, where two of them could be associated with a Sardinian origin.
Miniaturized bronze flasks represent a small portion of a wide metallurgical production that flourished in Sardinia (Italy) between the Final Bronze Age (FBA) and the Early Iron Age (EIA). They replicate a well-known and symbolic type of object, the pilgrims’ flask, common in all Europe and Mediterranean basin, and have but few archaeological parallels. For these reasons, their characterization can be considered important from an archaeological perspective. Three flasks, preserved at the Antiquarium Arborense museum (Oristano), were analyzed by X-Ray Fluorescence Spectroscopy (XRF) and Raman spectroscopy, integrated by multispectral images. The samples, coming from illegal excavations, posed two problems: establishing their authenticity and investigating the alloy composition of such particular objects. All specimens presented a widespread degradation in the outer surface: XRF and Raman spectroscopy indicated the presence of copper oxides, calcium and copper carbonates deposits. The abscence of Zn, a clear marker of forgeries, was not detected by XRF. In two of the flasks, an unusual Sn content above 20%, was detected. For FBA and EIA, especially regarding southern Europe, Sn was extremely rare, and was possibly used with caution. Further results are presented herein.