1931. How size of target avalanches influences prediction efficiencyAlexander Shapoval, M. Shnirman, 2004, original scientific article Abstract: Bak, Tang, and Wiesenfeld [Phys. Rev. Lett.59, 381 (1987)] introduced their sand-pile (BTW sand-pile) as the cellular automata coming to their critical state without tuning any inner model parameters. The main model features deal with grains falling slowly onto the two-dimensional lattice and a quick deterministic transport of the superfluous grains to the boundary. The simplest modifications of the BTW sand-pile develop a random transport mechanism instead of a deterministic one. The model transportation of the grains generates avalanches. We find that before the big avalanches the height of the pile increases and the singular grains organize themselves in special clusters. These observations lead to the formal algorithm that predicts the big avalanches in advance with a certain efficiency. However the efficiency for the BTW sand-pile is worse than that for its stochastic modifications.
Keywords: sandpile, prediction, avalanches
Published in RUNG: 19.04.2021; Views: 1676; Downloads: 0
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1932. Strong events in the sand-pile modelAlexander Shapoval, M. Shnirman, 2004, original scientific article Abstract: Here is a sand-pile introduced by Bak et al. The system accumulates particles one by one. From time to time it topples. Every toppling initiates an event. The distribution of the events' size follows a power law for all the events except the strongest ones. The fraction of the strongest events does not depend on the system length. The number of particles and their clustering increase before the strongest events.
Keywords: sandpile, prediction, power-law
Published in RUNG: 19.04.2021; Views: 1771; Downloads: 0
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1933. Two regimes in the regularity of sunspot numberAlexander Shapoval, Jean-Louis Le Mouël, Vincent Courtillot, M. Shnirman, 2013, original scientific article Abstract: Sunspot numbers WN display quasi-periodical variations that undergo regime changes. These irregularities could indicate a chaotic system and be measured by Lyapunov exponents. We define a functional λ (an "irregularity index") that is close to the (maximal) Lyapunov exponent for dynamical systems and well defined for series with a random component: this allows one to work with sunspot numbers. We compute λ for the daily WN from 1850 to 2012 within 4 yr sliding windows: λ exhibit sharp maxima at solar minima and secondary maxima at solar maxima. This pattern is reflected in the ratio R of the amplitudes of the main versus secondary peaks. Two regimes have alternated in the past 150 yr, R1 from 1850 to 1915 (large λ and R values) and R2 from 1935 to 2005 (shrinking difference between main and secondary maxima, R values between 1 and 2). We build an autoregressive model consisting of Poisson noise plus an 11 yr cycle and compute its irregularity index. The transition from R1 to R2 can be reproduced by strengthening the autocorrelation a of the model series. The features of the two regimes are stable for model and WN with respect to embedding dimension and delay. Near the time of the last solar minimum (~2008), the irregularity index exhibits a peak similar to the peaks observed before 1915. This might signal a regime change back from R2 to R1 and the onset of a significant decrease of solar activity.
Keywords: Lyapunov exponent, solar activity, solar cycle
Published in RUNG: 19.04.2021; Views: 1868; Downloads: 59
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1934. Determination of Aethalometer multiple-scattering enhancement parameters and impact on source apportionment during the winter 2017/18 EMEP/ACTRIS/COLOSSAL campaign in MilanVera Bernardoni, Luca Ferrero, Ezio Bolzacchini, Alice Corina Forello, Asta Gregorič, Dario Massabo, Griša Močnik, Paolo Prati, Martin Rigler, Luca Santagostini, 2021, original scientific article Abstract: In the frame of the EMEP/ACTRIS/COLOSSAL campaign in Milan during winter 2018, equivalent black carbon measurements using the Aethalometer 31 (AE31), the Aethalometer 33 (AE33), and a Multi-Angle Absorption Photometer (MAAP) were carried out together with levoglucosan analyses on 12 h resolved PM2.5 samples collected in parallel.
From AE31 and AE33 data, the loading-corrected aerosol attenuation coefficients (bATN) were calculated at seven wavelengths (λ, where λ values are 370, 470, 520, 590, 660, 880, and 950 nm). The aerosol absorption coefficient at 637 nm (babs_MAAP) was determined by MAAP measurements. Furthermore, babs was also measured at four wavelengths (405, 532, 635, 780 nm) on the 12 h resolved PM2.5 samples by a polar photometer (PP_UniMI).
After comparing PP_UniMI and MAAP results, we exploited PP_UniMI data to evaluate the filter multiple-scattering enhancement parameter at different wavelengths for AE31 and AE33. We obtained instrument- and wavelength-dependent multiple-scattering enhancement parameters by linear regression of the Aethalometer bATN against the babs measured by PP_UniMI. We found significant dependence of the multiple-scattering enhancement parameter on filter material, hence on the instrument, with a difference of up to 30 % between the AE31 and the AE33 tapes. The wavelength dependence and day–night variations were small – the difference between the smallest and largest value was up to 6 %.
Data from the different instruments were used as input to the so-called “Aethalometer model” for optical source apportionment, and instrument dependence of the results was investigated. Inconsistencies among the source apportionment were found fixing the AE31 and AE33 multiple-scattering enhancement parameters to their usual values. In contrast, optimised multiple-scattering enhancement parameters led to a 5 % agreement among the approaches.
Also, the component apportionment “MWAA model” (Multi-Wavelength Absorption Analyzer model) was applied to the dataset. It was less sensitive to the instrument and the number of wavelengths, whereas significant differences in the determination of the absorption Ångström exponent for brown carbon were found (up to 22 %).
Keywords: black carbon, filter photometer, Aethalometer, source apportionment
Published in RUNG: 16.04.2021; Views: 2329; Downloads: 0
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1936. Timing techniques applied to distributed modular high-energy astronomy : the HERMES projectA. Sanna, Aurora Clerici, P. Efremov, Dejan Gačnik, Andreja Gomboc, Uroš Kostić, Mile Karlica, David Selčan, 2020, published scientific conference contribution Keywords: nanosateliti, izbruhi sevanja gama, astrofizika
Published in RUNG: 16.04.2021; Views: 2235; Downloads: 69
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1937. GrailQuest & HERMES : hunting for gravitational wave electromagnetic counterparts and probing space-time quantum foamLuciano Burderi, Aurora Clerici, P. Efremov, Dejan Gačnik, Andreja Gomboc, Uroš Kostić, Mile Karlica, David Selčan, 2020, published scientific conference contribution Keywords: nanosateliti, izbruhi sevanja gama, astrofizika
Published in RUNG: 16.04.2021; Views: 2081; Downloads: 64
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1939. The scientific payload on-board the HERMES-TP and HERMES-SP CubeSat missionsY. Evangelista, Aurora Clerici, P. Efremov, Dejan Gačnik, Andreja Gomboc, Uroš Kostić, Mile Karlica, David Selčan, 2020, published scientific conference contribution Keywords: nanosateliti, izbruhi sevanja gama, astrofizika
Published in RUNG: 15.04.2021; Views: 2318; Downloads: 58
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1940. The HERMES-technologic and scientific pathfinderF. Fiore, Aurora Clerici, P. Efremov, Darja Gačnik, Andreja Gomboc, Uroš Kostić, Mile Karlica, David Selčan, 2020, published scientific conference contribution Keywords: nanosateliti, izbruhi sevanja gama, astrofizika
Published in RUNG: 15.04.2021; Views: 2157; Downloads: 59
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