12064 research outputs found
Sort by
An analytical model for predicting the magnetization loss in HTS sector-shaped conductors for fusion
Get PDFWithin the framework of magnetic confinement fusion, several projects worldwide are demonstrating the possibility of integrating high-temperature superconductors (HTS) in the coil systems. HTS-based technologies are highly attractive for practical applications because they can extend the operating margins of fusion coils in terms of higher temperatures, transport currents and magnetic fields. Based on the results achieved with the twisted-stacked tape cable, we have designed a novel low-loss HTS sector cable-in-conduit conductor, with a target of 60 kA at 4.5 k, 18 T, which is presently of interest for the DEMO Central Solenoid coil. In HTS cables, the AC losses can represent a significant limiting factor, therefore they must be taken into consideration both in the design phase and in the assessment of the overall magnet thermal budget. In this work, to assess the loss behavior and to optimize the cable design, we have explored different aspect ratios and arrangements of the stacked tapes within the cable layout. The magnetization losses are calculated with a 2D finite-element model based on the T-A formulation and analytical approximations based on the Brandt-Halse critical state model. Specifically, we have developed an analytical formulation that allows for the calculation of the instantaneous power losses in HTS stacked cables with a limited number of tapes per stack, achieving sufficient accuracy at high fields. The analytical model enables a sufficiently accurate assessment of the heat deposited on the conductor during those particular instants of a plasma scenario where the variation of the field is very high, such as during the critical initial discharge period of the plasma initiation
Prospective regional analysis of olive and olive fly in Andalusia under climate change using physiologically based demographic modeling powered by cloud computing
Get PDFThe Spanish region of Andalusia is the world-leading olive oil producer. Its olive-dominated landscapes are among the most biodiverse drylands of the globe and prospectively among the areas most affected by climate change. This analysis used physiologically based demographic modeling (PBDM) to assess the impact of climate change on the olive/olive fly system of Andalusia. The analysis was implemented on cloud computing, allowing PBDM models to be run from any computer connected to the internet, to interface with state-of-the-art climatic drivers, and to scale efficiently with increasing computational loads and user requests. Findings include that chilling required for olive blooming will decrease in large areas of the Andalusian provinces of Jaen, Cordoba, and Sevilla, with some areas not meeting the minimum chilling threshold and some accumulating no chilling by the end of the century under the high greenhouse gas (GHG) emission scenario. Olive blooming will occur up to five weeks earlier in the Jaen, Cordoba, Sevilla, and Granada provinces, but olive yield is expected to increase or remain stable. Olive fly infestation will decrease with climate change, with infestations below the reference economic threshold of 4 % towards the end of the century in some areas under high GHG emission scenario. Measures to adapt Andalusian olive systems to climate change include: selecting olive cultivars with lower chilling requirements; implementing cover crops to enhance water use efficiency under increased CO2 concentration and uncertain precipitation projections; and targeting the spring generation of the fly and diversifying the olive landscape to reduce infestation levels
Exfoliation of Molecular Solids by the Synergy of Ultrasound and Use of Surfactants: A Novel Method Applied to Boric Acid
Get PDFBoric acid, H3BO3, is a molecular solid made up of layers held together by weak van der Waals forces. It can be considered a pseudo “2D” material, like graphite, compared to graphene. The key distinction is that within each individual layer, the molecular units are connected not only by strong covalent bonds but also by hydrogen bonds. Therefore, classic liquid exfoliation is not suitable for this material, and a specific method needs to be developed. Preliminary results of exfoliation of boric acid particles by combination of ultrasound and the use of surfactants are presented. Ultrasound provides the system with the energy needed for the process, and the surfactant can act to keep the crystalline flakes apart. A system consisting of a saturated solution and large excess solid residue of boric acid was treated in this way for a few hours at 40 °C in the presence of various sodium stearate, proving to be very promising, and an incipient exfoliation was achieved
A High–Throughput Molecular Dynamics Study for the Modeling of Cryogenic Solid Formation
Get PDFTo predict the favorable thermodynamical conditions and characterize cryogenic pellet formations for applications in nuclear fusion reactors, a high–throughput molecular dynamics study based on a unified framework to simulate the growth process of cryogenic solids (molecular deuterium, neon, argon) under gas pressure have been designed. These elements are used in fusion nuclear plants as fuel materials and to reduce the damage risks for the plasma-facing components in case of a plasma disruption. The unified framework is based on the use of workflows that permit management in HPC facilities, the submission of a massive number of molecular dynamics simulations, and handle huge amounts of data. This simplifies a variety of operations for the user, allowing for significant time savings and efficient organization of the generated data. This approach permits the use of large-scale parallel simulations on supercomputers to reproduce the solid–gas equilibrium curves of cryogenic solids like molecular deuterium, neon, and argon, and to analyze and characterize the reconstructed solid phase in terms of the separation between initial and reconstructed solid slabs, the smoothness of the free surfaces and type of the crystal structure. These properties represent good indicators for the quality of the final materials and provide effective indications regarding the optimal thermodynamical conditions of the growing process
Photo-Thermal Dry Reforming of Methane with PGM-Free and PGM-Based Catalysts: A Review
Get PDFDry reforming of methane (DRM) is considered one of the most promising technologies for efficient greenhouse gas management thanks to the fact that through this reaction, it is possible to reduce CO2 and CH4 to obtain syngas, a mixture of H2 and CO, with a suitable ratio for the Fischer–Tropsch production of long-chain hydrocarbons. Two other main processes can yield H2 from CH4, i.e., Steam Reforming of Methane (SRM) and Partial Oxidation of Methane (POM), even though, not having CO2 as a reagent, they are considered less green. Recently, scientists’ challenge is to overcome the many drawbacks of DRM reactions, i.e., the use of precious metal-based catalysts, the high temperatures of the process, metal particle sintering and carbon deposition on the catalysts’ surfaces. To overcome these issues, one proposed solution is to implement photo-thermal dry reforming of methane in which irradiation with light is used in combination with heating to improve the efficiency of the process. In this paper, we review the work of several groups aiming to investigate the pivotal promoting role of light radiation in DRM. Focus is also placed on the catalysts’ design and the progress needed for bringing DRM to an industrial scale
The Mu2e crystal and SiPM calorimeter
Get PDFThe calorimeter of the Mu2e experiment is being assembled, with all production components completed and tested, apart from the digital electronics that is still underway. The mechanical structure is fully built, with a complete integration and test of all the analog sensors and electronics. We summarize construction and assembly phases, Quality Control tests, calibration procedures and first tests performed in the assembly area, as well as the installation and commissioning plans of the final disks in the Mu2e hall
Heat Supply to Industrial Processes via Molten Salt Solar Concentrators
Get PDFAbout one-third of world energy production is destined to the industrial sector, with process heat accounting for about 70% of this demand; almost half of this quota is required by endothermic processes operating at temperatures above 400 °C. Concentrated solar thermal technology, thanks to cost-effective high-temperature thermal energy storage solutions, can respond to the renewable thermal energy needs of the industrial sector, thus supporting the decarbonization of hard-to-abate processes. Particularly, parabolic trough technology using binary molten salts as heat transfer fluid and storage medium, operating up to 550 °C, could potentially supply a large part of the high-temperature process heat required by the industry. In this work, four industrial processes, representative of the Italian industrial context, that are well suited for integration with molten salt concentrators are presented and discussed, conceiving for each considered process a specific coupling solution with the solar plant, sizing the solar field and the thermal storage unit, and computing the cost of the process heat and its variation with the storage capacity. Considering cost data from the literature associated with the pre-COVID-19 era, an LCOH comprising the range 5–10 c€/kWhth was obtained for all the cases studied, while taking into account more updated cost data, the calculated LCOH varies from 7 to 13 c€/kWhth
Polar Stratospheric Cloud Observations at Concordia Station by Remotely Controlled Lidar Observatory
Get PDFPolar stratospheric clouds (PSCs) form in polar regions, typically between 15 and 25 km above mean sea level, when the local temperature is sufficiently low. PSCs play an important role in the ozone chemistry and the dehydration and denitrification of the stratosphere. Lidars with a depolarization channel may be used to detect and classify different classes of PSCs. The main PSC classes are water ice, nitric acid trihydrate (NAT), and supercooled ternary solutions (STSs), the latter being liquid droplets consisting of water, nitric acid, and sulfuric acid. PSCs have been observed at the lidar observatory at Concordia Station from 2014 onward. The harsh environmental conditions at Concordia during winter render successful lidar operation difficult. To facilitate the operation of the observatory, several measures have been put in place to achieve an almost complete remote control of the system. PSC occurrence is strongly correlated with local temperatures and is affected by dynamics, as the PSC coverage during the observation season shows. PSC observations in 2021 are shown as an example of the capability and functionality of the lidar observatory. A comparison of the observations with the satellite-borne CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar has been made to demonstrate the quality of the data and their representativeness for the Antarctic Plateau
Analysis of the integral zeolite molecular sieve process for helium CPS application
Get PDFZeolite Molecular Sieves (ZMSs) are commonly adopted in tritium handling facilities for impurity removal from gaseous streams, particularly for tritiated water trapping. Several activities have been conducted to characterize the adsorption and desorption behaviour of the sieving materials. Instead, less attention has been put on the analysis of the integral process comprising the adsorption of the tritiated humidity, the regeneration of the molecular sieve and the recovery of the desorbed water. Focusing on the application for the EU-DEMO helium Coolant Purification System (CPS), this work presents a process simulator relying on a MATLAB dynamic model of the ZMS bed and on a RELAP5/MOD3.3 model for the regeneration loop. The dynamic model can simulate both the adsorption and regeneration modes of the ZMS by providing the temperature and the adsorbate concentration profile along the column, while the thermal-hydraulic model is used to assess the conditions of the regeneration loop. By coupling the outcomes of the two models it is possible to establish the effective regeneration efficiency of the process and the amount of the tritiated water recovered. For the case of helium CPS, the analysis demonstrates the feasibility of the proposed operative scheme and the capabilities of the regeneration procedure to ensure a 74.4 % regeneration efficiency of the ZMS bed
Progettazione e realizzazione di una scheda elettronica per sensori elettrochimici di gas inquinanti dell'atmosfera
Get PDFIl monitoraggio della qualità dell'aria è effettuato dalle agenzie preposte con strumentazione basata su tecnologie estremamente affidabili, ma che comportano costi elevati, sia per quanto riguarda l'acquisto degli strumenti stessi, sia per ciò che concerne la loro manutenzione e gestione. Un alternativa a tali tecnologie è rappresentata dai sensori elettrochimici per gas che, sebbene siano caratterizzati da minore accuratezza, presentano vantaggi quali: costi molto contenuti, alto livello di miniaturizzazione, e necessità di manutenzione pressoché nulla. Tra i sensori per gas inquinanti presenti nell'ambiente, quelli che offrono le prestazioni più interessanti sono rappresentati dai sensori a celle elettrochimiche. Per il funzionamento di tali dispositivi, è necessario un circuito elettronico appositamente progettato che è realizzato su schede elettroniche solitamente fornite dall'azienda produttrice dei sensori. Il lavoro presentato in questo documento concerne la progettazione e realizzazione di una scheda elettronica per la serie "B" dei sensori elettrochimici prodotti dalla Alphasense. Tale azienda fornisce schede elettroniche su cui è possibile installare solo un singolo sensore, ma non dà la possibilità di usare più tipi di sensori in contemporanea. Tale caratteristica limita fortemente il livello di miniaturizzazione dei dispositivi per il monitoraggio della qualità dell'aria il cui funzionamento si basa su tali sensori. Questa, ed altre limitazioni, hanno motivato la progettazione e realizzazione di una nuova scheda elettronica, della quale vengono illustrati i dettagli progettuali e realizzativi in questo documento.Air quality monitoring is performed by on-purpose agencies through instrumentation based on extremely reliable technologies, but featured by high costs, both as concerning their purchase, and their maintenance and management. An option for these technologies is represented by the electrochemical gas sensors which, even though characterized by a lower accuracy, offer some advantages, such as: low costs, high miniaturization grade, and no maintenance. Among the gas sensors designed for air quality monitoring, the most interesting are the ones based on the electrochemical cells. To operate such sensors, it is necessary an electronic circuit typically implemented on electronic boards provided by the sensor manufacturer. The work exposed in this document regards the design and implementation of an electronic board to support the operation of the “B” series of the electrochemical gas sensors produced by Alphasense. This brand provides electronic boards on which it is possible to install only one sensor, but they do not allow the use of more sensors at the same time. This feature heavily restrains the grade of miniaturization of the devices which design is based on such sensors. To overcome this and other limitations, a new electronic board has been designed and implemented. In this document, its design and the implementation details are exposed