Multifractal characterization of stochastic resonance

We use a multifractal formalism to study the effect of stochastic resonance in a noisy bistable system driven by various input signals. To characterize the response of a stochastic bistable system we introduce a new measure based on the calculation of a singularity spectrum for a return time sequence. We use wavelet transform modulus maxima method for the singularity spectrum computations. It is shown that the degree of multifractality defined as a width of singularity spectrum can be successfully used as a measure of complexity both in the case of periodic and aperiodic (stochastic or chaotic) input signals. We show that in the case of periodic driving force singularity spectrum can change its structure qualitatively becoming monofractal in the regime of stochastic synchronization. This fact allows us to consider the degree of multifractality as a new measure of stochastic synchronization also. Moreover, our calculations have shown that the effect of stochastic resonance can be catched by this measure even from a very short return time sequence. We use also the proposed approach to characterize the noise-enhanced dynamics of a coupled stochastic neurons model.Comment: 10 pages, 21 EPS-figures, RevTe

Synthesis, Crystal Structure and Luminescent Properties of Pyrovanadates A2CaV2O7 (A = Rb, Cs)

The novel vanadium oxides Rb2CaV2O7 and Cs2CaV2O7 have been prepared by solid-state reaction and their crystal structures determined and refined using X-ray, neutron powder and electron diffraction data. Rb2CaV2O7 and Cs2CaV2O7 are isostructural, crystallizing in space group P21/n with unit cell parameters: a = 13.8780(1), b = 5.96394(5), c = 10.3376(1) Å, β = 104.960(1)° and a = 14.0713(2), b = 6.0934(1), c = 10.5944(1) Å, β = 104.608(1)°, respectively. Their crystal structures can be described as a framework of CaO6 octahedra and V2O7 pyrogroups with alkaline metals found in the tunnels formed. Photoluminescence (PL) and PL excitation spectra of the considered pyrovanadates have been studied in the vacuum ultraviolet (VUV) to visible light (Vis) range as well as their pulse cathode luminescence (PCL) spectra and the kinetic parameters of PCL. In the PL and the PCL spectra of both pyrovanadates recorded at T = 300 K a broad band with maxima at 2.2, 2.4 eV and two shoulders (bands) at 2.0 and 2.58 eV have been observed. At T = 10 K the band at 2.0 eV becomes the main band in the spectra. Two types of luminescence centers for each pyrovanadate, with very similar excitation bands at 3.75, 4.84, 6.2, 7.3 and 9.1 eV, have been found. The nature of the luminescence centers connected with the bands at 2.0, 2.2, 2.4 and 2.58 eV is discussed. © 2008 Elsevier Masson SAS. All rights reserved.This work was supported by the Russian–American program “Fundamental research and higher education” (CRDF REC-005: grant EK-005-X1 fund of the Ural Scientific Educational Center “Perspectivnie materiali”), by the Russian Foundation for Basic Research under Grant No. 07-03-00143, by the Council for Grants of the President of the Russian Federation for Support of Young Scientists (grant no. MK–84.2007.3) and ICDD Grant-in-Aid № 93-09 (2005–2006). Gunnar Svensson wants to thank the Swedish research council for financial support

RADIATION-OPTICAL PROPERTIES OF RARE-EARTH ION DOPED ALYMINIUM OXYNITRIDE

Pulsed cathodoluminescence and X-ray luminescence spectra of Al50 6N:Ce3+ and A1506N:Eu2+ have been investigated. The concentration dependencies of luminescence intensity have been measured and discussed.Работа выполнена при финансовой поддержке Минобрнауки РФ (стипендия Президента РФ - 2015) и УрФУ (грант молодым ученым - кандидатам наук)

CATHODOLUMINESCENCE OF ALUMINUM OXYNITRIDE Al5O6N WITH DOUBLE DOPING BY RARE-EARTHED IONS

Pulsed cathodoluminescence of aluminum oxynitride Al5O6N doped with Er3+, Ho3+ and Ho3+, Tm3+ ions has been measured. The narrow lines registered at 460, 480 and 663 nm are related to 1D2→3F4, 1G4→3H4 transitions in Tm3+ ion and 5F5→6I8 transition in Ho3+ ion.Работа выполнена при поддержке Российского Фонда Фундаментальных Исследований (проект РФФИ № 17-03-00630_а)

NEW OPTICAL MATERIALS BASED ON ALUMINUM OXYNITRIDE

Aluminum oxynitride is a promising compound for creating optical ceramics for designing phosphors, LED components and radiation detectors. Our research is focused on luminescent properties of Ce- and Eu-doped aluminum oxynitride Al5O6N

THERMOLUMINESCENT DETECTOR BASED ON ALUMINUM OXYNITRIDE Al5O6N:Ce3+

The new working medium for thermoluminescent dosimetry based on Сe-doped aluminum oxynitride has been proposed. It has a number of advantages for radiation monitoring due to low temperature of main dosimetric peak, high luminescence quantum yield and upper limit of linear dose dependence range at 60 Gy

PHOTOLUMINESCENCE OF ALUMINUM OXYNITRIDE Al5O6N DOPED WITH RARE-EARTH IONS

Photoluminescence (PL) spectra and pulsed PL decay curves of aluminum oxynitride Al5O6N (ALON) doped with Ce3+ and Eu2+ ions were measured. In PL spectra broad bands with maximum at 380 nm (ALON:Ce) and 500 nm (ALON: Eu) related to d-f transitions in rare-earth ions are observed. Pulsed PL decay curves approximated with exponential expression with one component (ALON:Ce) and two components (ALON: Eu), de-cay times is 24 ns and 313 ns, 1025 ns respectively.Работа выполнена при поддержке Российского Фонда Фундаментальных Исследований (проект РФФИ № 17-03-00630_а)