51. Mass composition of Telescope Array's surface detectors events using deep learningI. Kharuk, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: We report on an improvement of deep learning techniques used for identifying primary particles of atmospheric air showers. The progress was achieved by using two neural networks. The first works as a classifier for individual events, while the second predicts fractions of elements in an ensemble of events based on the inference of the first network. For a fixed hadronic model, this approach yields an accuracy of 90% in identifying fractions of elements in an ensemble of events. Keywords: Telescope Array, indirect detection, ground array, surface detection, ultra-high energy, cosmic rays, composition, deep learning, machine learning, neural networks Published in RUNG: 29.09.2023; Views: 951; Downloads: 4 Full text (788,87 KB) This document has many files! More... |
52. Telescope Array anisotropy summaryI. Tkachev, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: In this talk, we summarise the results of recent anisotropy studies conducted by the Telescope Array (TA) collaboration. At largest scales we test the TA data for the presence of a dipole. On smaller scales, an update on the excess of events in the direction of Ursa Major previously found in the TA data will be presented. These flux variations may trace the distribution of UHECR sources. We will examine the data for correlations with large-scale structures in the nearby Universe, and as a result, hints for the chemical composition of primaries will be provided. We also discuss a related anisotropy of the UHECR spectrum. Keywords: Telescope Array, indirect detection, ground array, surface detection, ultra-high energy, cosmic rays, composition, energy spectrum, anisotropy Published in RUNG: 29.09.2023; Views: 703; Downloads: 4 Full text (1,83 MB) This document has many files! More... |
53. Downward Terrestrial Gamma-ray Flashes at the Pierre Auger Observatory?R. Colalillo, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, published scientific conference contribution Abstract: At the Pierre Auger Observatory, designed primarily to study ultra-high-energy cosmic rays, phenomena related to atmospheric electricity are also observed. Particularly, events have been detected with the surface detector, characterized by long-lasting signals (tens of microseconds) and event footprints much larger (up to 200 km2) than those produced by the highest energy cosmic rays. Moreover, some of them appear to be accompanied by smaller events occurring in the same area within about 1 ms and probably produced by the same phenomenon. A previously reported correlation with the World Wide Lightning Location Network, as well as the observation of very low-altitude clouds, confirm that such events are related to thunderstorms. An ad-hoc reconstruction points to high-energy particles being produced very close to the ground, suggesting that they originate from electrons accelerated to relativistic energies in strong electric fields inside low clouds, as is the case for terrestrial gamma-ray flashes above thunderstorms.
A clear explanation of the observed phenomenon is hindered by two facts. One is that the rate of such events, detected serendipitously, is very small (less than 2 events/year) and decreases further after optimization of the surface detector trigger for low-energy shower-events. The second is that most events show a puzzling lack of signals in the central part of the footprint. We have studied in detail both effects and will present such studies here. We developed a strategy for a dedicated trigger to enhance the detection efficiency for these events associated with atmospheric-electricity events. Keywords: Pierre Auger Observatory, surface detection, ultra-high energy, cosmic rays, photons, electrons, gamma-ray flashes, lightning Published in RUNG: 29.09.2023; Views: 814; Downloads: 6 Full text (2,42 MB) This document has many files! More... |
54. Performance and simulation of the surface detector array of the TAx4 experimentK. Fujisue, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: The TAx4 experiment is a project to observe highest energy cosmic rays by expanding the detectionarea of the Telescope Array (TA) experiment with newly constructed surface detectors (SDs) andfluorescence detectors (FDs). New SDs are arranged in a square grid with 2.08 km spacing atthe north east and south east of the TA SD array. We use CORSIKA simulations and implementthe calibration data of the new SDs to calculate the performance of the new SDs. We comparethe data with the simulation and validate the performance of the SDs. The comparison and theperformance will be shown in the presentation. Keywords: Telescope Array, TAx4, indirect detection, ground array, surface detection, ultra-high energy, cosmic rays, CORSIKA Published in RUNG: 29.09.2023; Views: 846; Downloads: 5 Full text (3,16 MB) This document has many files! More... |
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56. Electronic and chemical surface properties of Bi2Se3 derived compoundsZipporah Rini Benher, doctoral dissertation Keywords: Bismuth selenide derived compounds, surface chemical and electronic properties, topological insulators, single crystals, phase separation, inorganic bulk heterostructures, ix
Bridgman method, X-ray powder diffraction, scanning electron microscopy, photoelectron spectroscopy Published in RUNG: 16.12.2022; Views: 1813; Downloads: 24 Full text (9,56 MB) |
57. CO[sub]2 activation over nanoshaped CeO[sub]2 decorated with nickel for low-temperature methane dry reformingKristijan Lorber, Janez Zavašnik, Iztok Arčon, Matej Huš, Janvit Teržan, Blaž Likozar, Petar Djinović, original scientific article Abstract: Dry reforming of methane (DRM) is a promising way to
convert methane and carbon dioxide into H2 and CO (syngas). CeO2
nanorods, nanocubes, and nanospheres were decorated with 1−4 wt % Ni.
The materials were structurally characterized using TEM and in situ
XANES/EXAFS. The CO2 activation was analyzed by DFT and
temperature-programmed techniques combined with MS-DRIFTS. Synthesized CeO2 morphologies expose {111} and {100} terminating facets,
varying the strength of the CO2 interaction and redox properties, which
influence the CO2 activation. Temperature-programmed CO2 DRIFTS
analysis revealed that under hydrogen-lean conditions mono- and bidentate
carbonates are hydrogenated to formate intermediates, which decompose
to H2O and CO. In excess hydrogen, methane is the preferred reaction
product. The CeO2 cubes favor the formation of a polydentate carbonate
species, which is an inert spectator during DRM at 500 °C. Polydentate covers a considerable fraction of ceria’s surface, resulting in
less-abundant surface sites for CO2 dissociation Keywords: surface carbonates, in situ characterization, Ni XANES, Ni EXAFS, spectator species, CeO2 nanoshapes, CO2 activation Published in RUNG: 13.07.2022; Views: 1645; Downloads: 0 This document has many files! More... |
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60. Fractal and inertia moment analyses for thin film quality monitoringMohanachandran Nair Sindhu Swapna, 2022, original scientific article Abstract: The widespread applications of thin films in optronics demand innovative techniques for its characterizations. The work reported here proposes electronic speckle pattern interferometry and fractal-based methods for assessing the quality of thin films taking the industrially relevant molybdenum oxide (MoO3) incorporated niobium oxide (Nb2O5) films. The films with different levels of MoO3 incorporation (1, 2, 3, 5, and 10 wt. %) are prepared by radio frequency sputtering. The study reveals the structure modifications of Nb2O5 from the orthorhombic to monoclinic phases with an associated morphological variation revealed through atomic force microscopy and field-emission scanning electron microscopy analyses. The films’ specklegrams are recorded under thermal stress; the inertia moment (IM) and fractal analyses are computed and compared with the root-mean-square surface roughness of the films. The lacunarity analysis of the AFM films agrees well with the specklegrams. Thus, the lower IM and lacunarity values of the specklegrams can be regarded as indicators of the good quality of thin films. Keywords: cross-correlation, fractal dimension, inertia moment, lacunarity, speckle, surface roughness. Published in RUNG: 30.06.2022; Views: 1365; Downloads: 0 This document has many files! More... |