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1.
Using muon rings for the optical throughput calibration of the Cherenkov Telescope Array
Markus Gaug, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution

Abstract: Muon ring images observed with Imaging Atmospheric Cherenkov Telescopes (IACTs) provide a powerful means to calibrate the optical throughput of IACTs and monitor their optical point spread function. We investigate whether muons ring images can be used as the primary optical throughput calibration method for the telescopes of the future Cherenkov Telescope Array (CTA) and find several additional systematic effects in comparison to previous works. To ensure that the method achieves the accuracy required by CTA, these systematic effects need to be taken into account and minor modifications to the hardware and analysis are necessary. We derive analytic estimates for the expected muon data rates to be used for optical throughput calibration, monitoring of the optical point spread function, with achievable statistical and systematic uncertainties, and explore the potential of muon ring images as a secondary method of camera pixel flat-fielding.
Keywords: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array (CTA) Observatory, Imaging Atmospheric Cherenkov Telescopes, IACT optical throughput calibration, IACT camera pixel flat-fielding, IACT optical point spread function (PSF), muon ring images
Published in RUNG: 13.11.2024; Views: 246; Downloads: 5
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2.
Intra- and inter-city variability of ▫$PM_2.5$▫ concentrations in Greece as determined with a low-cost sensor network
Konstantinos Dimitriou, Iasonas Stavroulas, Georgios Grivas, Charalampos Chatzidiakos, Georgios Kosmopoulos, Andreas Kazantzidis, Konstantinos Kourtidis, Athanasios Karagioras, Nikolaos Hatzianastassiou, Spyros N. Pandis, 2023, original scientific article

Abstract: Measurements of PM2.5 concentrations in five major Greek cities over a two-year period using calibrated low-cost sensor-based particulate matter (PM) monitors (Purple Air PA-II) were combined with local meteorological parameters, synoptic patterns and air mass residence time models to investigate the factors controlling PM2.5 spatiotemporal variability over continental Greece. Fourteen sensors nodes in Athens, Patras, Ioannina, Xanthi, and Thermi (in the Metropolitan Area of Thessaloniki) were selected out of more than 100 of a countrywide network for detailed analysis. The cities have populations ranging from 65k to 3M inhabitants and cover different latitudes along the South-North axis. High correlations between the daily average PM2.5 levels were observed among all sites, indicating strong intra- and inter-city covariance of concentrations, both in cold and warm periods. Higher PM2.5 concentrations in all cities during the cold period were primarily associated with low temperatures and stagnant anticyclonic conditions, favoring the entrapment of residential heating emissions from biomass burning. Anticyclonic conditions were also connected to an increased frequency of PM2.5 episodes, exceeding the updated daily guideline value (15 μg m−3) of the World Health Organization (WHO). During the warm period, nearly uniform PM2.5 levels were encountered across continental Greece, independently of their population size. This uniformity strongly suggests the importance of long-range transport and regional secondary aerosol formation for PM2.5 during this period. Peak concentrations were associated mainly with regional northern air flows over Greece and the Balkan Peninsula. The use of the measurements from dense air quality sensor networks, provided that a robust calibration protocol and continuous data quality assurance practices are followed, appears to be an efficient tool to gain insights on the levels and variability of PM2.5 concentrations, underpinning the characterization of spatial and seasonal particularities and supporting real-time public information and warning.
Keywords: particulate matter, PM2.5, biomass burning, low-cost sensors, purple air PA-II, concentration weighted trajectory, potential source contribution function
Published in RUNG: 10.05.2024; Views: 906; Downloads: 4
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3.
Arithmetic functions associated with hypergroups
Irina Elena Cristea, 2023, published scientific conference contribution abstract

Keywords: hypergroups, Euler's function, fuzzy grades, commutativity degrees
Published in RUNG: 05.07.2023; Views: 2274; Downloads: 4
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New aspects in the theory of complete hypergroups
Irina Elena Cristea, 2023, published scientific conference contribution

Keywords: complete hypergroup, reversibility, period of an element regularity, reducibility, class equation, commutativity degree, Euler's totient function
Published in RUNG: 20.06.2023; Views: 1981; Downloads: 12
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Eulerʹs totient function applied to complete hypergroups
Andromeda Cristina Sonea, Irina Elena Cristea, 2023, original scientific article

Keywords: Euler's totient function, complete hypergroups, period of an element, heart of a hypergroup
Published in RUNG: 19.01.2023; Views: 2237; Downloads: 7
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Estensioni di Stone del teorema di approssimazione di Weierstrass
Federico Mangano, undergraduate thesis

Keywords: Function approximation, geometry
Published in RUNG: 23.11.2022; Views: 1668; Downloads: 0
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