3,203 research outputs found

    Theoretical backgrounds of durability analysis by normalized equivalent stress functionals

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    Generalized durability diagrams and their properties are considered for a material under a multiaxial loading given by an arbitrary function of time. Material strength and durability under such loading are described in terms of durability, safety factor and normalized equivalent stress. Relations between these functionals are analysed. We discuss some material properties including time and load stability, self-degradation (ageing), and monotonic damaging. Phenomenological strength conditions are presented in terms of the normalized equivalent stress. It is shown that the damage based durability analysis is reduced to a particular case of such strength conditions. Examples of the reduction are presented for some known durability models. The approach is applicable to the strength and durability description at creep and impact loading and their combination

    Search for invisible decays of sub-GeV dark photons in missing-energy events at the CERN SPS

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    We report on a direct search for sub-GeV dark photons (A') which might be produced in the reaction e^- Z \to e^- Z A' via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The A's would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75\cdot 10^{9} electrons on target. We set new limits on the \gamma-A' mixing strength and exclude the invisible A' with a mass < 100 MeV as an explanation of the muon g_\mu-2 anomaly.Comment: 6 pages, 3 figures; Typos corrected, references adde

    Dark Matter Search Perspectives with GAMMA-400

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    GAMMA-400 is a future high-energy gamma-ray telescope, designed to measure the fluxes of gamma-rays and cosmic-ray electrons + positrons, which can be produced by annihilation or decay of dark matter particles, and to survey the celestial sphere in order to study point and extended sources of gamma-rays, measure energy spectra of Galactic and extragalactic diffuse gamma-ray emission, gamma-ray bursts, and gamma-ray emission from the Sun. GAMMA-400 covers the energy range from 100 MeV to ~3000 GeV. Its angular resolution is ~0.01 deg(Eg > 100 GeV), and the energy resolution ~1% (Eg > 10 GeV). GAMMA-400 is planned to be launched on the Russian space platform Navigator in 2019. The GAMMA-400 perspectives in the search for dark matter in various scenarios are presented in this paperComment: 4 pages, 4 figures, submitted to the Proceedings of the International Cosmic-Ray Conference 2013, Brazil, Rio de Janeir

    ТЕОРЕТИЧЕСКИЕ И ЭКСПЕРИМЕНТАЛЬНЫЕ ИССЛЕДОВАНИЯ ПО ОПРЕДЕЛЕНИЮ СТРУЙНОГО ДАВЛЕНИЯ РАБОЧЕЙ ЖИДКОСТИ НА ОБРАБАТЫВАЕМУЮ ПЛОСКУЮ ПОВЕРХНОСТЬ

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    A mathematical model for  calculation of a jet power impact on a barrier consisting of a corrosive deposit layer  has been proposed on the basis of an upper-bound method and accepted assumptions. A variational problem associated with determination of a minimum destruction pressure has been solved and a theoretical dependence for pressure calculation at the point of jet-barrier collision with due account of mechanical properties of the destroyed material and kinematic jet parameters has been obtained in the paper. Comparison of experimental data obtained by means of the EDP-30 sensor with the theoretical ones has shown a divergence of 15–19 % within velocity range of the jet impact from 150 to 300 m/s.На основе метода верхней оценки и принятых допущений предложена математическая модель для расчета силового воздействия струи на преграду, состоящую из слоя коррозионных отложений. Решена вариационная задача, связанная с нахождением минимального давления разрушения, получена теоретическая зависимость для расчета давления в точке соударения струи с преградой, учитывающая механические свойства разрушаемого материала, а также кинематические параметры струи. Сопоставление экспериментальных данных, полученных с помощью датчика ЭДП-30, с теоретическими в диапазоне скоростей струйного воздействия 150–300 м/с показало расхождение 15–19 %
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